Embed Size (px)
Citation preview
The Pennsylvania State University
The Graduate School
Department of Architectural Engineering
METHODOLOGY FOR DESIGN, CALIBRATION, SYSTEM IDENTIFICATION
AND OPERATION OF AN EXPERIMENTAL HVAC SYSTEM
A Thesis in
Architectural Engineering
by
Li Cui
2013 Li Cui
Submitted in Partial Fulfillment
of the Requirements
for the Degree of
Master of Science
May 2013
ii
The thesis of Li Cui was reviewed and approved* by the following:
Stephen Treado
Associate Professor of Architectural Engineering
Thesis Advisor
James D. Freihaut
Professor of Architectural Engineering
Jelena Srebric
Professor of Architectural Engineering
Chimay Anumba
Department Head & Professor of Architectural Engineering
*Signatures are on file in the Graduate School
iii
ABSTRACT
It is well known that building control systems rarely function as designed, contributing to
excessive energy use and poor environmental control performance. In addition, most
conventional building control systems do not incorporate many energy efficient functions thereby
missing potential energy savings opportunities. Part of the reason for this problem is the lack of
effective modeling and simulation tools for building control systems, and the difficulty in
obtaining the information required to accurately model specific HVAC components and systems,
along with the difficulty of implementing and exercising the models at the design stage. Also,
models that have been verified by laboratory or field measurements are lacking, putting into
doubt the validity of simulation results when they are undertaken.
In order to address these issues, this project will focus on the design and construction of
an HVAC experimental system with control capability, system performance identification and
development of components characteristics. The facility consists of an air handling unit with
heating and cooling coils, a water heater, a chiller and a chilled water storage tank. Two
customized chambers are constructed for both outdoor and indoor air simulation which allows the
system to be operated under various realistic conditions. Tests will be conducted using the facility
first for system performance identification, and second to develop and evaluate different
component characteristics.
This document includes a literature review about different HVAC control strategies and
an overview of several HVAC control test centers in the United States. The procedure of design
and constructing an experimental HVAC system and the performance identification are also
presented.
iv
TABLE OF CONTENTS
LIST OF FIGURES ........................................................................................................... vi
LIST OF TABLES ........................................................................................................... viii
Chapter 1 INTRODUCTION ............................................................................................. 1
1.1 Background ............................................................................................................................ 1
1.2 Objectives .............................................................................................................................. 5
Chapter 2 LITERATURE REVIEW .................................................................................. 7
2.1 HVAC Control ....................................................................................................................... 7
2.1.1 Classical Control ............................................................................................................. 7
2.1.2. Auto-tuning PID Control ............................................................................................... 8
2.1.3 Optimal Control .............................................................................................................. 9
2.1.6 Direct Digital Control (DDC) ....................................................................................... 10
2.1.4 Non-linear Control ........................................................................................................ 10
2.1.5 Fuzzy Logic Control ..................................................................................................... 11
2.1.7 MIMO Robust Control .................................................................................................. 12
2.2 HVAC System Simulation ................................................................................................... 13
2.3 HVAC System Modeling ..................................................................................................... 15
Chapter 3 REVIEW OF HVAC SYSTEM TEST CENTERS ......................................... 16
3.1 Iowa Energy Center-Energy Resource Station (ERS) ......................................................... 16
3.2 Lawrence Berkeley National Laboratory (LBNL) ............................................................... 19
3.2.1 Building Controls Virtual Test Bed .............................................................................. 19
3.2.2 Modelica Buildings Library .......................................................................................... 20
3.3 Syracuse University-Full Scale Thermal and Air Quality Research Facility ...................... 21
Chapter 4 EXPERIMENTAL HVAC AND CONTROL SYSTEM ............................... 23
4.1 HVAC System Design ......................................................................................................... 24
4.1.1 Load Calculation ........................................................................................................... 24
4.1.2 Pipe and Duct Sizing ..................................................................................................... 26
4.1.3 Control System Design ................................................................................................. 30
4.2 HVAC and Control System Setup ....................................................................................... 31
4.2.1 Equipment ..................................................................................................................... 31
4.2.2 Piping and Ducting ....................................................................................................... 37
4.2.2 Control Instruments ...................................................................................................... 41
v
4.2.3 Control Modules Installation and Power Enclosure ..................................................... 46
4.2.4 Insulation for the HVAC System .................................................................................. 49
4.3 Software Development for Control Operation and Data Acquisition .................................. 50
4.3.1 Control System Setup in MAX and LabVIEW ............................................................. 53
Chapter 5 SYSTEM OPERATION AND PERFORMANCE IDENTIFICATION ........ 58
5.1 Equipment and System Operation ....................................................................................... 58
5.1.1 Chilled Subsystem Operation ....................................................................................... 58
5.1.2 Hot Water Subsystem Operation .................................................................................. 60
5.1.3 Air Handler Unit Operation .......................................................................................... 62
5.1.4 AHU Cooling/Heating Coil Subsystem Operation ....................................................... 64
5.1.5 HXZ and HXO Subsystem Operation ........................................................................... 65
5.2 System Performance Identification ...................................................................................... 67
5.2.1 Steady State Verification .............................................................................................. 67
5.2.2 Energy Balance Identification ....................................................................................... 70
5.3 Characteristics of the System Components .......................................................................... 78
5.3.1 Outdoor Box ................................................................................................................. 78
5.3.2 Indoor Box .................................................................................................................... 80
Chapter 6 ANALYSIS AND DISCUSSION ................................................................... 82
6.1 Experimental HVAC System Design vs. Actual Operation ................................................ 82
6.2 Measurement Uncertainty and Sensor Calibration .............................................................. 82
6.3 System Control Capability ................................................................................................... 83
Chapter 7 CONTRIBUTIONS AND RECOMMENDATIONS ..................................... 84
7.1 Contribution to HVAC Control Test Facility ...................................................................... 84
7.2 Future Work Recommendations .......................................................................................... 84
Appendix LABVIEW PROGRAMMING ...................................................................... 86
REFERENCES ................................................................................................................. 91
vi
LIST OF FIGURES
Figure 1 Building Share of U.S. Primary Energy Consumption (Percent) ...................................... 1
Figure 2 Major Fuel Consumptions by End Use for All Buildings, 2003 ....................................... 2
Figure 3 PID control (McDowall 2009) ........................................................................................... 8
Figure 4 Schematic Diagram of System Model (House and Smith 1995) ....................................... 9
Figure 5 Comparison of the performances between the fuzzy controller and the PI controller on a
non-linear model (Ying et al. 1990) ............................................................................................... 12
Figure 6 Diagram of the experimental system and interface signals (M. Anderson et al. 2007) ... 13
Figure 7 Block Diagram of the Serial Communication (Modified) Virtual Instrument (Liew 2003)
....................................................................................................................................................... 14
Figure 8 HVAC Plan for Test Rooms (Iowa Energy Center 2010) ............................................... 17
Figure 9 Typical Test Room AHU (Iowa Energy Center 2010) .................................................... 19
Figure 10 Ptolemy II system model that links an actor with MatLab (LBNL 2011) ..................... 20
Figure 11 Full Scale Thermal and Air Quality Research Facility (BEEL at SU 2010) ................. 21
Figure 12 HVAC System Scheme ................................................................................................. 23
Figure 13 System and Pump Curves .............................................................................................. 28
Figure 14 HVAC System 3D Layout ............................................................................................. 28
Figure 15 Sensor Placement Scheme ............................................................................................. 30
Figure 16 Portable Air Cooled Chiller ........................................................................................... 32
Figure 17 SPI Control of the Chiller .............................................................................................. 32
Figure 18 Hot Water Heater ........................................................................................................... 33
Figure 19 Expansion Tank and Water Filters ................................................................................ 33
Figure 20 Side Glass for the Storage Tank .................................................................................... 34
Figure 21 Air Handling Unit .......................................................................................................... 35
Figure 22 Outdoor Box .................................................................................................................. 36
Figure 23 Outdoor Box .................................................................................................................. 36
Figure 24 Indoor Box ..................................................................................................................... 37
Figure 25 Copper Piping and Components ................................................................................... 38
Figure 26 Filters ............................................................................................................................. 38
Figure 27 Circulating Pump ........................................................................................................... 39
Figure 28 Leakage Test .................................................................................................................. 39
Figure 29 Support Base for Water Heater ...................................................................................... 40
Figure 30 Adjustable Clamps ......................................................................................................... 40
Figure 31 3-Way Control Valve .................................................................................................... 41
Figure 32 RTD ............................................................................................................................... 42
Figure 33 RTD Calibration ............................................................................................................ 42
Figure 34 Water Flow Meter .......................................................................................................... 43
Figure 35 Air Flow Station Control Panel ..................................................................................... 44
Figure 36 Air Flow Station Sensor Probe ...................................................................................... 44
Figure 37 Partition of Supply and Return Ducts ............................................................................ 45
Figure 38 Partition of Outdoor Duct .............................................................................................. 45
Figure 39 NI Control Modules ....................................................................................................... 47
vii
Figure 40 Power Distribution Unit ................................................................................................ 48
Figure 41 System Control Desk ..................................................................................................... 49
Figure 42 Insulation of the HVAC System .................................................................................... 49
Figure 43 Measurement and Automation Explorer (MAX) Operation Window ........................... 53
Figure 44 Controller Configurations in LabVIEW ........................................................................ 54
Figure 45 Main Operation VI for the Summer Condition.............................................................. 55
Figure 46 Chilled Water Storage Subsystem Operation VI ........................................................... 55
Figure 47 Water Temperature Indicators ....................................................................................... 56
Figure 48 TDMS File for Water Temperatures ............................................................................. 57
Figure 49 Supply Water Temperatures .......................................................................................... 68
Figure 50 Water Flow Rates ......................................................................................................... 68
Figure 51 Air Temperatures ........................................................................................................... 69
Figure 52 Air Flow Rates ............................................................................................................... 70
Figure 53 Installed Valve Characteristics for HXO Hot Water ..................................................... 78
Figure 54 Installed Valve Characteristic for HXO Chill ............................................................... 79
Figure 55 Output and Process Variable Chart ............................................................................... 80
Figure 56 Installed Valve Characteristic for HXZ Hot Water ....................................................... 81
Figure 57 Installed Valve Characteristic for HXZ Chill ................................................................ 81
Figure 58 Data Logging Main VI .................................................................................................. 86
Figure 59 Chilled Water Storage Control VI ................................................................................. 86
Figure 60 System Monitor VI ........................................................................................................ 87
Figure 61 Summer Operation Main VI .......................................................................................... 88
Figure 62 Summer Monitor VI ...................................................................................................... 89
Figure 63 Winter Operation VI ...................................................................................................... 90
viii
LIST OF TABLES
Table 1 Design Conditions ............................................................................................................. 25
Table 2 Load Calculation ............................................................................................................... 25
Table 3 Pipe Sizing ........................................................................................................................ 27
Table 4 Equipment Schedule ......................................................................................................... 29
Table 5 Sensor Schedule ................................................................................................................ 31
Table 6 Signal Schedule ................................................................................................................. 46
Table 7 Control Modules Specification ......................................................................................... 47
Table 8 System Outputs ................................................................................................................. 51
Table 9 Test Conditions - Summer ................................................................................................ 70
Table 10 Test Conditions - Winter ................................................................................................. 71
Table 11 Outdoor Simulation Heat Exchanger Load Calculations – Summer (Heating) .............. 71
Table 12 Outdoor Simulation Heat Exchanger Load Calculations – Winter (Cooling) ................ 72
Table 13 Indoor Simulation Heat Exchanger Load Calculations – Summer (Heating) ................. 73
Table 14 Indoor Simulation Heat Exchanger Load Calculations – Winter (Cooling) ................... 74
Table 15 AHU Heat Exchanger Load Calculations – Summer (Cooling) ..................................... 75
Table 16 AHU Heat Exchanger Load Calculations – Winter (Heating) ........................................ 76
Table 17 Overall System Energy Balance ..................................................................................... 77
ix
ACKNOWLEDGEMENTS
I would like to thank my advisor Dr. Treado whose instruction and expertise in HVAC
control is the central driver of my research and graduate study. The plentiful guidance,
encouragement and assistance he gave me are deeply appreciated.
I am also grateful to my committee member Dr. James Freihaut and Dr. Jelena Srebric
who helped to identify this topic and provided me this great research opportunity.
Special recognition is due to Mr. Paul Kremer who provided useful guidance and
assistance throughout the HVAC system construction and control program development. Thanks
are also due to fellow research assistant Samuel Fonseca Soto for his assistance during the
construction of the project, configuration of the control modules, especially the assembly of
electrical facilities, to Ke Xu and Yan Chen for their assistance on the control system design and
LabVIEW development, and to Hiroki Ota whose assistance and encouragement throughout the
project.
I would also like to thank all the other fellow graduate students who provided me with
great moral support and assistance.
x
DEDICATION
To my parents
1
Chapter 1
INTRODUCTION
1.1 Background
In recent years, building energy consumption is in a rising trend, as shown in Figure 1.
Building sectors consumed 33.8% of the total primary energy use in 1980 which increased to 40%
by the year 2008. These primary energy consumptions include industry and manufacturing,
transportation and building sectors. 84% of energy consumed is attributed to building operations
such as heating, cooling and lighting. The sharp increase in building energy consumption raises
concerns of energy savings in building operation.
Figure 1 Building Share of U.S. Primary Energy Consumption (Percent)
HVAC system energy usage has a significant impact on buildings’ fuel consumption by
end use, as shown in Figure 2. One of the ways to realize sizable decrease in building energy
consumption is applying better HVAC control systems.
30.0%
32.0%
34.0%
36.0%
38.0%
40.0%
42.0%
Per
cen
tage
Year
Building Share of U.S. Primary Energy Consumption
2
Figure 2 Major Fuel Consumptions by End Use for All Buildings, 2003
A wide range of equipment is involved in HVAC systems, to name a few general
components: chillers, compressors, boilers and pumps. HVAC control systems aim to operate the
equipment efficiently as well as provide a high quality environment. In operation, each HVAC
system should be suitable for the requirements in the facility; in combination, HVAC system
controls provide the link between varying thermal loads and maintaining suitable indoor
environmental conditions. The designed HVAC system will not operate as expected without an
adequately designed and properly functioning control system (McDowall 2009). A control loop
generally includes a controller, a sensor and a control device. The controller compares the data
from sensors with the set point or the desired value, relaying a command to the controlled device,
which passes to the process plant. The command will have an effect on the controlled variable
and then the process will start all over again.
Space Heating, 36%
Lighting, 20%
Cooling, 8%
Ventilation, 7%
Water Heating, 8%
Cooking, 3%
Refrigeration, 6%
Office Equipment, 1%
Computers, 2%
Other, 9%
3
Over a century ago, the first control device-the bimetallic strip was applied for space-
heating systems. It controlled boiler output or air combustion damper, which were known as
regulators. These regulators, now called thermostats are used to control temperature in various
circumstances and functions, such as cars, restaurants, and houses. In the 1950’s, pneumatic
sensors and controllers were used in commercial buildings to control the heated or cooled air flow.
At that time the pneumatic controllers had to be installed and supervised by the controls
manufacturer resulting in highly expensive implementation that could not easily be used
nationwide. Improved pneumatic control systems were widely used in industry by the 1960’s.
Electronic HVAC control systems appeared in the 1970’s which was known as micro-
chip analog electric controls. These controllers were used to connect or break an electric circuit
that turns on a fan or pump, as well as switch a valve or damper. Initial computer based systems
were costly and performed minimal control functions. The need for affordable controllers led to
the development of pneumatic controls in favor of electrical controls.
In the late 20th century, the development and use of computers and microprocessors have
triggered great changes in HVAC control systems. Microprocessors made it possible for remote
data acquisition and direct digital control. Computers were used as on-site controllers and became
efficient tools in an integrated HVAC control system.
There are basically five control types today: self-powered controls are that controllers do
not require an external power source such as electricity or pneumatic control air. These systems
generally used on small HVAC systems or individual units. The most common and basic
controller is one of the electric controllers called thermostat. Electric controls are most typically
two positions, using thermostats, humidistats, or pressure-stats where the controlled variable is
sensed and compared to the set point and a contact is opened and closed accordingly. The other
4
kind of electric controls is modulating controllers, which are used as a bridge circuit. Pneumatic
controls use compressed air as the power source. They are simple and cheap, which make it ideal
for temperature, humidity and pressure control. Analog electric controls are known as typical
modern controls. Several electric controllers are packaged in a single zone for controlling the
whole system. However, they are not as popular as pneumatic controls for commercial buildings
due to their high cost and lack of standardization. Digital control is the most advanced control
which means the microprocessors can operated on a series of pulses just as the typical PC.
Intelligent control strategies focus on providing a better control of indoor environment
while using less energy. As processing capabilities increased, more and more studies focused on
advanced HVAC controllers such as fuzzy control and robust control. However, most of the
studies are based on simulation and modeling results, while this may indicate the potential
benefits of advanced control strategies, translating the predictive performance into an actual
installation is not guaranteed. In order to prove the effectiveness of new control strategies and
designs, it is necessary to conduct validation testing using real HVAC systems. Verification of the
accuracy of dynamic models of actual HVAC systems also plays an essential role in controller
design and calibration.
There are a number of HVAC control system modeling and simulation tools currently
available with varying degrees of complexity and capability. Many of the tools impose significant
simplifying assumptions and idealizations that make them easier to use but also limit their ability
to realistically model control system performance. At the other extreme, a few tools require very
specialized knowledge and skill to use, two attributes that are generally not part of the normal
skill set HVAC control designs. Several general purpose simulation tools are being proposed for
use on this project.
5
MatLab (Matrix Laboratory) is a high-level technical computing language and interactive
environment for algorithm development, data analysis and numerical computation. MatLab can
be applied in a wide range of fields such as control design, test and measurement, modeling and
simulating processes. Architectural engineers can use it to develop dynamic models of HVAC
systems for controller development and calibration.
Simulink is a commercial tool for simulation, model based design of dynamic systems. The
interactive graphic environment and a set of block libraries enable engineers and scientists to
design, simulate, implement and test a variety of time-varying systems such as communications,
controls and signal processing.
LabVIEW (short for Laboratory Virtual Instrumentation Engineering Workbench) is a
graphical programming environment used by engineers and scientist to develop sophisticated
measurement, test, and control systems by using graphic icons and wires that resemble a
flowchart. The purpose of this programming is automating the usage of processing and measuring
equipment in any laboratory setup. LabVIEW is commonly used for data acquisition, instrument
control, and industrial automation on a variety of platforms including Microsoft Windows,
various versions of UNIX, Linux, and Mac OS X. The latest version of LabVIEW is version
LabVIEW 2011, released in August 2011.
1.2 Objectives
An experimental HVAC system will be designed, constructed, configured, and
commissioned, including a control and a data acquisition system. The HVAC system is designed
for both heating and cooling conditions, using two chambers for outdoor and indoor condition
simulations. An air handler, electric heater, air cooled chiller, heat exchangers and 3-way valves
are the basic components of the experimental HVAC system. An integrated software environment
6
will be created for data acquisition and control using LabVIEW. During the system identification
stage, tests will be conducted to enable the development of dynamic models of each of the
components. Different model types will be investigated and compared relative to their level of
effort to complete and their accuracy and performance. Several goals will be achieved in this
project:
Design, construct and commission an experimental HVAC system for control
performance evaluation
Develop test facility control and data acquisition software:
o Providing system control functions
o Conducting dynamic tests
o Collecting and processing measured data
Conduct system performance tests to provide measured data for system and components
identification
Determine component characteristics for modeling
7
Chapter 2
LITERATURE REVIEW
There are a wide array of articles pertaining to HVAC controls studies. A brief literature
review is completed and presented in the following.
2.1 HVAC Control
The HVAC control history consists of classical control and advanced control according to
the control requirement. The common purpose on various control modes is to maintain the
controlled variable at the desired set point.
2.1.1 Classical Control
Classical control is known as the traditional and most economic control modes. There are
two subgroups in classical control: On/Off control and PID (proportional, integral plus derivative)
control.
On/Off control is also called two-position control which only provides two outputs, on or
off (Harrold and Lush 1988). It is widely used in residential houses for starting or stopping a
thermostat. Ahn and Song (2010) studied the on/off control characteristics and heating
performances for a radiant slab heating system in residential apartments (Ahn and Song 2010).
The fact is that the control doses not maintain the indoor air set point and creates a fluctuation in
temperature. They concluded it is important to set the proper point and use a differential gap.
PID control (see Figure 3) is generally applied to systems with continuous or modulating
capacity capability, it may also be applied to systems with staged capacity capability to improve
the accuracy versus two-position control logic (McDowall 2009).
8
Figure 3 PID Control (McDowall 2009)
Classic controllers have the relatively acceptable function and low cost. However, with
regard to the efficiency and energy consumption, advanced controllers are more cost and energy
effective.
2.1.2. Auto-tuning PID Control
Turning a PID controller requires an accurate model of a process and an effective
controller design rule. Auto-tuning relieves the pain of manually tuning a controller. PID auto-
tuning means automatically determine PID parameters without human intervention (McDowall
2009)
(Ya-Gang Wang et al. 2001) developed a PID auto-tuner and presented its application to
HVAC systems. They found that the PID turning rules with accurate identification method has a
better control performance than the standard relay auto-tuner.
Although auto-tuning control can offer many advantages and are normally superior to the
PID control, this approach is limited to large range applications because model identification is
9
required as initial step, together with model parameter identification in real time mode (Mirinejad
et al. 2008).
2.1.3 Optimal Control
The goal of optimal control is to determine the minimum energy usage or operating cost
for the system to achieve the desired comfort level. In comparison to conventional control
strategies, optimal control has been demonstrated to have the potential for energy savings of 12 to
30 percent (Nizet et al. 1984).
A comparison of optimal control with conventional control for a two-zone building and
HVAC system (Figure 4) is presented in (House and Smith 1995). The utility cost for the
optimum case is 11 percent less than the utility cost for the conventional cost. This difference is
mainly attributed to the cooling coil energy term and cost even less by allowing the temperature
in the zones to float within a predefined comfort range.
Figure 4 Schematic Diagram of System Model (House and Smith 1995)
10
(Komareji et al. 2008) established a HVAC system which is made of two heat exchangers
and the optimal control structure was designed and implemented. Dynamic model of the system
was developed. The results of applying the developed control system showed that the system
respected optimal control policy while it had the perfect tracking of the set point of the inlet air
temperature. However, there is a problem with the bypass flow which cannot satisfy the
optimization criteria. A controller is then introduced to deal with this problem in (Komareji et al.
2009) and a simplified control structure is finally proposed for optimal control of the HVAC
system.
2.1.6 Direct Digital Control (DDC)
DDC systems can reduce energy cost by enabling mechanical systems to operate at peak
efficiency. The DDC technology can be used in diverse applications, such as commercial HVAC,
surgical suites, and laboratory clean rooms (McDowall 2009).
(Swanson 1993) discussed the most common deficiencies of conventionally controlled
HVAC systems and advantages of DDC systems. DDC offers an array of features to correct some
of the operation and maintenance problems identified, while also reducing HVAC system energy
consumption. A case study retrofit from pneumatic control to digital control is also studied in this
paper. By avoiding the cost of installing a new HVAC system, the applied DDC system realized
annual savings and improved indoor air quality.
2.1.4 Non-linear Control
Since HVAC systems are essentially a non-linear system, a number of Non-linear
Controllers are designed and utilized in HVAC systems since the 80’s (Mirinejad et al. 2008).
(Bing Dong 2010) introduces several non-linear optimal controllers for a single zone
heating system in buildings. MatLab/ Simulink response optimizer and non-linear programming
11
are applied into optimal controller design and the results are compared. Linearization makes the
controller design easier but results in the fan consuming more energy. The non-linear
programming results in much less energy cost for both the fan and pump. This conclusion is not
only useful in the optimal controller design but also in the predictive controller design when real-
time weather files could be forecasted.
A back-stepping controller for a non-linear, MIMO HVAC system is demonstrated by
(Semsar et al. 2003). Using feedback linearization method, heat and moisture loads can be
compensated, considering them as measureable disturbances. The simulation results are brought
to show the ability of the method to present a controller with high disturbance decoupling and
good tracking properties.
2.1.5 Fuzzy Logic Control
The main problem in HVAC systems are variable conditions, intense non-linear factors,
interaction between climatic parameters, variation in system parameters and impossibility of
accurate modeling of the system (Mirinejad et al. 2008). With regard to the problems, fuzzy logic
control will be an excellent controlling choice.
(Ying et al. 1990) compared the function of the fuzzy controller with a non-fuzzy linear
PI controller. The control performances of the two controllers were almost the same; however, the
fuzzy controller could control the time-delay process model and non-linear process model
significantly better than the non-fuzzy linear PI controller (see Figure 5).
Fuzzy modeling methods for non-linear system identification and control design from
process data were reviewed and attention was paid to the choice of a suitable fuzzy model
structure for the identification task by (Babuška and Verbruggen 1996). An algorithm has also
been proposed for FLC design. A control policy for non-linear system was generated by
12
developing a number of local linear models and designing optimal control policies for each of
these local models (J. Singh et al. 2006).
Figure 5 Comparison of the performances between the fuzzy controller and the PI
controller on a non-linear model (Ying et al. 1990)
2.1.7 MIMO Robust Control
Robust control theory addresses the effects that discrepancies between the model and the
physical system may have on the design and performance of linear feedback systems. (M.
Anderson et al. 2007) created an experimental HVAC system consisting of two air dampers, a
variable speed blower, and a heating coil and applied MIMO robust control strategies to the
system (Figure 6). As a result, the robust controller was able to make a coordinated change in
several actuators to achieve essentially independent control over the reference variables.
13
Figure 6 Diagram of the experimental system and interface signals (M. Anderson et al. 2007)
An adaptive and robust controller was design by (Ming-Li Chiang and Li-Chen Fu 2006)
for a non-linear MIMO HVAC system which is modeled with some unknown parameters and
uncertainties. The robust controller can tolerance system uncertainties and made the tracking
error to converge residue set.
2.2 HVAC System Simulation
Various control assist tools have been developed for HVAC simulation. Mathworks
provides a large number of tools and toolboxes such as MatLab, Simulink and FemLab. (Clarke
et al. 2002) gave a synthesis on the use of MatLab/Simulink for the improvement of buildings and
HVAC systems. An overview on the related tools than can be applied and the issues solved by
using them is also studied.
A complete code for solving a 2-D steady state heat transfer problem and the results are
given by (van Schijndel 2003) in order to show how FemLab works. FemLab models can be
exported and connected with MatLab/Simulink models, creating a flexible simulation
14
environment for combined PDE (partial differential equation) and ODE (ordinary differential
equation) based models.
(Liew 2003) used LabVIEW to do remote control of HVAC system. LabVIEW is chosen
instead of other programming languages because of its ease of programming and debugging.
LabVIEW is a graphical programming language (Figure 7). Almost other programming languages
use lines of text codes to create applications which make it difficult to create an application.
Figure 7 Block Diagram of the Serial Communication (Modified) Virtual Instrument
(Liew 2003)
15
2.3 HVAC System Modeling
Models for HVAC components, particularly heat exchangers, have been the subject of a
number of articles over the past thirty years (M. L. Anderson 2001). The ASHRAE publication
Reference Guide for Dynamic Models of HVAC Equipment (ASHRAE 1996) provides a concise
overview of the dynamic models available for HVAC related equipment such as air and water
handling, heating and cooling coils and control equipment.
(Platt et al. 2010) studied adaptive HVAC zone modeling for sustainable buildings. This
paper focuses on real-time HVAC zone model fittings and prediction techniques based on
physical principles, as well as the use of genetic algorithms for optimization.
EnergyPlus is a new building performance and energy simulation program with a lot of
capabilities. (“EnergyPlus” 2000) gives an introduction of EnergyPlus and its applications in
building simulation.
16
Chapter 3
REVIEW OF HVAC SYSTEM TEST CENTERS
3.1 Iowa Energy Center-Energy Resource Station (ERS)
The ERS was established for the purpose of examining various energy-efficiency
measures and demonstrating HVAC concepts. It is the only public facility in the United States
with the ability to simultaneously test and demonstrate multiple, full scale commercial building
systems in a real world environment (Iowa Energy Center 2010).
There are four matched pairs of test rooms allow for side-by-side comparisons of systems
in real time and in a controlled environment (see Figure 8). ERS has three separate air handling
units with three separate hydronic piping loops, which makes it possible for a wide variety of
performance testing options:
constant and variable air volume
dual duct
ventilation air only
perimeter heating
fan powered variable air volume
low temperature air distribution
unit ventilator
fan coil unit
custom system configurations
17
Figure 8 HVAC Plan for Test Rooms (Iowa Energy Center 2010)
Several different types of testing and research have been done in energy efficiency and
building controls:
fault detection and diagnostics testing
reverse airflow testing
18
validation and optimization of building energy control systems
building energy simulation software
testing of an adaptive fuzzy logic controller for HVAC applications
day lighting research projects
effect of return air configuration on building energy and indoor air quality
testing of lighting circuit power reducers
For the data acquisition and control system, ERS has one DDC system for general area
and two individually controlled systems for test rooms. The general control system for ERS is an
Ethernet network which allows the operator workstation or a remote workstation to communicate
with network controllers. There are several different components for the test room system. Each
test room is equipped with an air distribution system with VAV or reheat coil (see Figure 9).
Several control sequences were implemented in the test room controls: air handling unit
control sequence, outside air injection fan control sequence, variable air volume control sequence
and fan coil control sequence. Detailed operation of each control sequence can be found in (Iowa
Energy Center 2010). On/Off and PID controllers were applied to the whole control system and
intelligent control strategies have been rarely used in this system.
19
Figure 9 Typical Test Room AHU (Iowa Energy Center 2010)
3.2 Lawrence Berkeley National Laboratory (LBNL)
3.2.1 Building Controls Virtual Test Bed
The Building Controls Virtual Test Bed (BCVTB) is a software environment that allows
expert users to couple different simulation programs for co-simulation (LBNL 2011).
Typical applications of the BCVTB include:
Performance assessment of integrated building energy and controls systems.
Development of new control algorithms.
Formal verification of controls algorithms prior to deployment in a building in order to
reduce commissioning time.
20
The BCVTB is based on the Ptolemy II software which can link various simulation
programs such as Energy Plus and MatLab (see Figure 10). Ptolemy II’s graphical modeling
environment allows model development of control systems, physical devices and communication
systems.
Figure 10 Ptolemy II system model that links an actor with MatLab (LBNL 2011)
3.2.2 Modelica Buildings Library
The Modelica Buildings library is a free open-source library with dynamic simulation
models for building energy and control systems. The primary use of the library is for flexible and
fast modeling of building energy and control (LBNL 2011). The library is particularly suited for:
Rapid prototyping of new building systems
Analysis of the operation of existing building systems
Development, specification, verification and development of building controls within a
model-based design process
21
Reuse of models during operation for functional testing, for verification of control
sequences, for energy-minimizing controls, fault detection and diagnostics.
The control systems include continuous time controls and discrete time controls. Both of
the two controls have various models. The Modelica Buildings library also has a large variety of
dynamic models for heating and cooling systems which can be implemented to this project. The
system configuration and set points descriptions can be found at (LBNL 2011).
3.3 Syracuse University-Full Scale Thermal and Air Quality Research Facility
The full scale thermal and air quality research facility is a coupled indoor/outdoor
environmental simulator which has three main components (see Figure 13):
An indoor environmental chamber (16ft by 12ft by 10 t high)
An outdoor climate chamber (6.5ft by 12ft by 10ft high)
An removable “separation wall” or “test wall” between the indoor environmental
chamber and the outdoor climate chamber
Figure 11 Full Scale Thermal and Air Quality Research Facility (BEEL at SU 2010)
22
The indoor environment chamber is capable of simulating various indoor environmental
conditions including air temperature, relative humidity, air change rate and room air distribution.
The climate chamber is capable of simulating a wide range of outdoor weather conditions from
cold and dry winters to hot and humid summers, including air temperature, relative humidity and
dynamic wind pressure (BEEL at SU 2010). Both of the chambers use programmable DDC
control system which can evaluate the performance of the sensors and controllers. However, this
test facility is mainly focused on the indoor air quality and particle research, few experiments
have been done on the controller side.
23
Chapter 4
EXPERIMENTAL HVAC AND CONTROL SYSTEM
An experimental HVAC system with both simulated indoor and outdoor environment
chambers was built in Architectural Engineering Lab (see Figure 12). The system consists of an
air handling unit (AHU) with both heating coil (HC) and cooling coil (CC); an air-cooled portable
chiller connects to a storage tank and an electrical hot water heater. Each of the simulated
chambers includes two heat exchangers (HXO and HXZ). The system is designed to mimic the
operation of a typical HVAC system providing space conditioning including ventilation to a
single zone. Currently, there is a limitation on latent loads, but this feature is expected to be
added at a future time. The primary purpose of the experimental HVAC test facility is to develop
and demonstrate advanced control strategies on real systems. Thus, considerable operating
flexibility has built in to the facility.
Figure 12 HVAC System Scheme
24
In summer conditions, the AHU supplies 58.6°F (dry bulb temperature) air flowing
through the indoor chamber (HXZ), removing heat load and returning to the AHU. A part of the
return air mixed with the outdoor air goes through the cooling coil and then supplies to the zone
(HXZ). Chilled water goes through the cooling coil, cooling the mixed air. Hot water goes
through the outdoor chamber (HXO, in this study the laboratory air will be fed into the HXO),
heating the lab air to the simulated outdoor temperature. The heat load of the HXZ is also
supplied by the hot water.
In winter conditions, chilled water goes through the HXO, cooling the lab air to the
simulated outdoor temperature. Amount of the return air mixed with simulated outdoor air being
heated to 106.4°F and supplied to the HXZ. Chilled water also goes in the HXZ to simulate the
heat loss. The storage tank for chilled water is used to simulate thermal storage option.
4.1 HVAC System Design
4.1.1 Load Calculation
The load calculation is based on the design condition of the air handler unit. In addition,
the design temperatures and humilities are listed in Table 1, which are referring to ASHRAE
Fundamentals. The Philadelphia weather data is used as outdoor air conditions. The load
calculation results are listed in Table 2. The selection of the outdoor heat exchangers uses log-
mean temperature method. Since the lowest supply chilled water is 45 °F, the simulated outdoor
air temperature in winter condition can be as low as 47.6 °F.
25
Table 1 Design Conditions
Weather Data 1%
Philadelphia DB (°F) MCWB (°F) HR
Cooling 90.6 74.5 0.0166
Heating DB 99% (°F)
Heating 16.9
Design Indoor Conditions Heating (°F) Cooling (°F) HR
Indoor temp 68 75 0.0092
Indoor relative humidity N/A 50%
Table 2 Load Calculation
Sensible Load
CASE Amount of
OA (%)
Water Heater
Capacity (MBh)
Chiller Capacity
(MBh)
Heating Coil
Capacity (MBh)
Cooling Coil
Capacity (MBh)
To (F) Tz (F) Ts (F)
Cooling
0% 7.078 7.078 0 7.078 90.6 75 58.59
10% 8.424 7.751 0 7.751 90.6 75 58.59
20% 9.770 8.424 0 8.424 90.6 75 58.59
30% 11.116 9.097 0 9.097 90.6 75 58.59
40% 12.462 9.770 0 9.770 90.6 75 58.59
Heating
0% 9.490 9.490 9.490 0 47.6 68 90
10% 11.043 12.897 11.043 0 47.6 68 90
20% 12.595 16.305 12.595 0 47.6 68 90
30% 14.148 19.713 14.148 0 47.6 68 90
40% 15.701 23.120 15.701 0 47.6 68 90
Latent Load
CASE Amount of
OA (%)
Water Heater
Capacity (MBh)
Chiller Capacity
(MBh)
Heating Coil
Capacity (MBh)
Cooling Coil
Capacity (MBh)
HR_o HR_z HR_s
Cooling
0% 0.774 0.774 0.774 0.774 0.0166 0.0092 0.0096
10% 1.742 0.658 1.742 0.658 0.0166 0.0092 0.0096
20% 4.259 2.091 4.259 2.091 0.0166 0.0092 0.0096
30% 6.776 3.524 6.776 3.524 0.0166 0.0092 0.0096
40% 9.293 4.956 9.293 4.956 0.0166 0.0092 0.0096
26
4.1.2 Pipe and Duct Sizing
Equivalent length method was applied for pipe sizing in this project as shown in Table 3.
Besides, equal-friction method was used to sizing the duct system. Pumps are selected depending
on the total pressure drops calculated form the pipe sizing chart. The piping system and pump
curve are shown in figure 14. The supply and return ducts are sized to be 8 x 10 inches according
to the pressure drop. The system was designed in Revit MEP; equipment arrangements and
system layout depend on available lab space (Figure 13). The indoor environment simulation
chamber is 1m³ with an exhaust on one side and two heat exchangers to simulate the
cooing/heating load. The size of the outdoor air simulation chamber is based on the heat
exchangers. Detailed specifications of each component are listed in Table 4.
27
Table 3 Pipe Sizing
Section Size (in)
Flow rate (gpm)
Length
Fittings
Accessory ∆P/L ( ft.H2O/100' pipe)
Equiv Length of Fittings (ft.)
Frictional ∆P (ft. H2O)
Valve ∆P (ft.H2O)
Coil ∆P (ft.H2O)
Total ∆P (ft.H2O)
Transition Elbow Tee
1 3/4'' 4 1' 1''-3/4'' (1) 1 3-way control valve for chiller
4.60 0.00
2 3/4'' 4 5' 3 4.60 0.00
3 3/4'' 4 1'10'' 1 4.60 60.00 1.50 1.50
4 1/2'' 2.32 1'10'' 1 6.00 20.00 0.54 0.54
5 1/2'' 2.32 6'4'' 1 Control Valve AHU 6.00 30.00 0.81 7.36 1.84 10.01
6 1/2'' 2 11'8'' 2 2-way control valve HXO 5.00 60.00 1.62 6.42 6.93 14.97
7 1/2'' 2 16'4'' 4 3-way control valve HXZ 5.00 120.00 3.24 6.42 9.24 18.90
8 1/2'' 2 17' 4 check valve 5.00 180.00 4.86 4.86
9 1/2'' 2.32 5'9'' 1 1 check valve 6.00 90.00 2.43 2.43
10 1/2'' 2 11'2'' 3 check valve 5.00 90.00 2.43 2.43
11 1/2'' 2.32 1'2'' 1 6.00
12 3/4" 4 3' 3-way valve for chiller,
strainer, pump 4.60
13 3/4" 4 5' 1''-3/4'' (1) 1 1 4.60
14 3/4" 4 4'5'' 2 Ball valve 4.60
15 3/4" 4 1' Process bypass valve 4.60
1 3/4'' 4 4' 3/4''-1/2'' (1) 1 1 Air separator ,ball valve 4.60 90 2.25 2.25
2 1/2'' 2 7'10'' 2 2-way control valve HXO 6.00 60 1.62 6.42 6.93 14.97
3 1/2'' 2 2'8'' 1 6.00 20 0.54 0.54
4 1/2'' 1.58 6'8'' 1 Control Valve AHU 3.50 30 0.81 7.36 1.52 9.69
5 1/2'' 2 17'8'' 4 3-way control valve HXZ 6.00 120 3.24 6.42 9.24 18.90
6 1/2'' 2 17' 4 1 check valve 6.00 180 4.86 4.86
7 1/2'' 1.58 7' 1 check valve 3.50 90 2.43 2.43
8 1/2'' 2 3'2'' 1 6.00 60 1.62 1.62
9 1/2'' 2 8' 3 check valve 6.00 90 2.43 2.43
10 3/4" 4 4' 3/4''-1/2'' (1) 1 Ball valve 4.60
28
Figure 13 System and Pump Curves
Figure 14 HVAC System 3D Layout
0
20
40
60
80
100
120
140
0 2 4 6 8
Tota
l He
ad, f
t
Flow Rate, gpm
Pump
System
29
Table 4 Equipment Schedule
Name Description Numbers Specification
Air Handling Unit Supply hot and cool air to the simulated
indoor chamber
1 Cooling capacity: 11630 Btu/hr;
Heating capacity: 15780 Btu/hr;
Supply chilled water: 45°F, 2.32 gpm;
Supply hot water: 180°F or 150°F, 1.58gpm
Chiller Produce chilled water and deliver it to
storage tank or system
1 Capacity: 19640 Btu/hr;
Supply 45°F chilled water, 55°F return;
Flow rate 4.8 gpm;
208VAC, 60Hz;
Pipe connection: 3/4''
Electric hot water
heater
Produce hot water 1 Capacity; 15780 Btu/hr;
Supply 180°F hot water (could also use 150°F ), return 160°F (if use 150°F supplied
then return is 130°F);
Flow rate5.58 gpm; pipe connection: 3/4''
HXO (Outdoor heat
exchanger)
Simulate outdoor air using ambient lab air 2 Heating air case: capacity 3860 Btu/hr,
Water temperature: 180°F to 160°F ( or 150°F to 130°F),
Air temperature:75°F to 85°F
Cooling air case: capacity 3640 Btu/hr,
Water temperature: 45F to 55°F, air 75°F to 50°F
HXZ (Indoor heat
exchanger )
Simulate indoor environment using heat
exchanger or other panels
2 Heating air case: capacity 15780 Btu/hr,
Water temp 180°F to 160°F ( or 170°F to 150°F), in coming air temperature:59°F;
Cooling air case: capacity 11630 Btu/hr, water temp 45°F to 55°F, in coming air
106.38°F
Storage tank Store chilled water and then deliver to the
system
1 80 gallon for 20min supply, based on the chiller flow rate
Water connection size: 3/4''
Pumps Circulate chilled/heated water to system 1 Based on the total requirement of system, 25 psi for 4 gpm
Pipe size:3/4''
3 way control valves Change between chiller and storage modes 3 Used for chilled water supply and return
2-way control valves Control water flow rate goes through HXO 2 Control the water flow rate go into the heat exchangers
3-way control valves Control the flow rate in the AHU and HXZ 4 Hot and chilled water supply pipes of the AHU
30
4.1.3 Control System Design
For the control system design, the measurement points were determined first. The sensor
locations are shown in Figure 15. Since this project intends to achieve accurate control results,
RTD temperature sensors and air flow stations were chosen for parameter measurements. Control
valves were selected based on the water flow rate and temperature. Control modules used for
sensor connection and data acquisition were sized according to the sensor and control valve
wiring diagram. This sensor layout gave the ability of knowing the water temperature goes in and
out of each heat exchanger, heater and chiller and the flow rate goes in each heat exchanger as
well as the air flow rate and temperature of supply, return and outdoor air. All the sensor
specifications are listed in Table 5.
Figure 15 Sensor Placement Scheme
31
Table 5 Sensor Schedule
Sensors Specified Requirements
Name Description Range Accuracy Notes
Tc Chilled water temperature sensor (40-60)°F 1°F Analog Output
Th Hot water temperature sensor (60-190)°F 1°F Analog Output
Fw Water meter 0 to 3 gpm 0.1 gfm Analog Output
Tz Zone air temperature sensor (45-120)°F 1°F Analog Output
Fa Air flow station 0-500cfm ±2% Analog Output
4.2 HVAC and Control System Setup
After designing the system, a market research and purchases of all the equipment and
components for the project were done. Next will be the equipment assembling, piping and control
system construction. Once the system is finished, the power box and electrical wires need to be
all hooked up and connected to the controller.
4.2.1 Equipment
The main components of the HVAC system are the chiller, air handling unit, storage tank,
heater and heat exchangers. The selection of that equipment based on the schedule and
calculation which were done in the system design stage.
Since the chiller should be easily fit in a lab space and be able to connect to the control
module. A portable air cooled chiller with communication capabilities, which can accept inputs
and deliver outputs was selected as shown in Figure17. The chilled has 2 tons of cooling load and
a 1 hp pump designed for 5 gpm at 39 psi. The design flow rate is 5 gpm and design chilled water
temperature is 50°F, which can be cooled as low as 40°F. In addition, the following
32
communications are supported: process temperature set point; high temperature deviation; low
temperature deviation; to process temperature and process status.
Figure 16 Portable Air Cooled Chiller
Figure 17 SPI Control of the Chiller
An 80 gallons commercial electrical hot water heater is shown in Figure 18. It has two
elements of 6KW and the hot water temperature can range from 120°F to 180°F. An expansion
tank and two water filters installed as shown in Figure 19.
33
Figure 18 Hot Water Heater
Figure 19 Expansion Tank and Water Filters
In addition, an 80 gallons commercial storage tank was implemented for the chilled water
storage. In order to see the water level in the storage tank, a side glass was installed on the side of
34
it. Figure 20 shows the position of the side glass. All the extra holes on the tank were sealed to
prevent leakage.
Figure 20 Side Glass for the Storage Tank
As shown in Figure 21, the air handling unit consists of a vertical blower coil with
hydronic cooling and heating and a mixing box with damper actuators. The fan has a variable
speed frequency drive (VFD) which gives the capability of providing different air flow rates. The
air handling unit also comes with two 3-way control valves for the cooling and heating coils
which can be controlled through the controller. For the automatic control capability, the VFD and
damper actuators can communicate with a remote controller.
35
Figure 21 Air Handling Unit
Two heater exchangers were used to simulate the outdoor condition. They are tube-fin
liquid to air heat exchangers with 4500 BTU/Hour capacity. Figure 22 shows the outdoor box
which was built based on the size of the heat exchangers and the shape the heat exchangers.
Another two 10900 BTU/Hour heat exchangers were used for simulating the indoor loads.
They are also tube-fin water to air heat exchangers and the maximum temperature is 400°F.
Figure 23 shows the heat exchanger and their position in the indoor box.
36
Figure 22 Outdoor Box
The indoor box is a 1m³ sheet metal box which has two heater exchangers of 10900
BTU/Hour in the middle (as shown in Figure 24). The supply air goes from the top of the box and
the return is on the bottom. There is an exhaust on the bottom of the box used for air balance.
Figure 23 Outdoor Box
37
Figure 24 Indoor Box
4.2.2 Piping and Ducting
The piping in this project is cooper tube with pro-press connector, which is easily
attached and has more flexibility. Unions and shut off valves were used on each side of the
components, which gave the capability of un-attach the components if there is a problem (Figure
25). The other components used in the water line are water filters and circulating pumps.
38
Figure 25 Copper Piping and Components
Filters were used for the chilled and hot water (Figure 26). The chilled water filters are
located before and after the chiller. The maximum pressure and temperature are 150 psi and
100°F and the micron rating is 5. The hot water filters are located before and after the hot water
heater. The maximum pressure and temperature are 250 psi and 250°F.
Figure 26 Filters
39
As shown in Figure 27, two circulating pumps were used for the chilled and hot water
distribution. The maximum flow rate and pressure are 256 gph and 150 psi. The hot water pump
head was customized for hot water.
Figure 27 Circulating Pump
Soap water was used for the leakage test of the water pipes. Referring Figure 28, if there
are bulbs on the connections, which means it needs to be fixed.
Figure 28 Leakage Test
40
Every facility has its own support with casters which means that the equipment can be
moved right away (Figure 29). The pipes are supported by strut and adjustable clamps (Figure 30).
Figure 29 Support Base for Water Heater
Figure 30 Adjustable Clamps
41
4.2.2 Control Instruments
The control instruments include control valves, damper actuators, VFD for the fan, water
temperature sensors and flow meters, air flow stations, humidity sensors and air temperature
sensors in the indoor box.
There are two 3-way control valves in the chilled water storage and two 2-way control
valves for the outdoor box piping (see Figure 31). The valves are all proportional and run
between 2 to 10 volts. The run time of these valves are 90 seconds. The 3-way control valves of
the indoor box are used to bypass the rest of the flow. There are also one 3-way floating control
valve and two proportional valves for the chilled water storage loop used for the chiller and the
storage tank.
Figure 31 3-Way Control Valve
The damper actuators and VFD are as described in 4.2.1. The temperature sensors used
for the water system are RTD sensors with high accuracy (±0.12%). As shown in Figure 32, the
sensor includes a stainless steel probe stem and 1/8 NPT mounting fitting which fit for the cooper
fitting used in the water system. The other end of the sensor is an electrical terminal which can be
connected to the control module.
42
Figure 32 RTD
A rotating plate with a magnet and a RTD calibrator as shown in Figure 33 were used for
the calibration of the RTD sensors. By putting the calibrator and the RTD sensor in water, the
difference between them will record and a correct factor will be used if the difference is greater
than the accuracy of the RTD sensors.
Figure 33 RTD Calibration
The water meter is a piston type, variable area flow meter with solid state circuitry
including non-contact sensor electronics, electronic signal conditioning circuit, digital flow rate
and total indication and proportional analog output. The water flow rates were measured using
flow meter with analog outputs which can be connected to the control modules. As shown in
43
Figure 34, the flow meter also has a digital flow rate indicator so people can see the flow rate
directly from the flow meter. The measurement range is 0.5 to 5 gpm and with a 2% full scale
accuracy.
c
Figure 34 Water Flow Meter
Three air flow stations were implemented for the supply, return and outdoor air flow rate
and temperature measurements. The air flow station has analog output transmitter which includes
the capability for dedicated independent linear outputs for temperature and flow rate (see Figure
35). There are certain restrictions should be considered when installing the air flow stations such
as the air flow linearization in the ducts. The placement of the probes according to the
duct/plenum sensor probe placement procedure in the air flow station manual.
44
Figure 35 Air Flow Station Control Panel
The outdoor air flow has two probes and the supply and return stations have one probe
each. The sensor accuracy of the probe is ±2% for the air flow and ±0.15°F for the air
temperature. The sensor range is 0 to +5,000 fpm for the air flow and -20°F to 160°F for the air
temperature. The sensor probe implements advanced thermal dispersion technology which relates
the velocity of the air to the power dissipation and rise in temperature of a heated element in a
moving air stream Figure 36.
Figure 36 Air Flow Station Sensor Probe
45
An anemometer was using to calibrate the air flow rates measured by the air flow
stations. The equal area method was conducted referring to Figure 37 and 38. At first,
four small areas were made for the supply, return ducts and nine sections of the outdoor
duct. After comparing with the air flow station readings and the data measured by
anemometer, correction factors were being applied to the air flow station.
Figure 37 Partition of Supply and Return Ducts
Figure 38 Partition of Outdoor Duct
46
4.2.3 Control Modules Installation and Power Enclosure
The signal inputs and outputs are listed in Table 6 and all these signals are connected to
certain control modules. Control modules’ selection is based on the signal lists.
Table 6 Signal Schedule
Control Analog Input Signals
Device Analog signal type Quantity
RTDs 100 Ω (at 0°C)-3 wire 23
Air Flow Meters 0-5 Vdc 3
Water Flow meters 4-10 mA 6
2-way proportional valves feedback signal 2-10 Vdc 2
3-way proportional valves feedback signal 2-10 Vdc 2
Control Analog Outputs Signals
Device Analog signal type Quantity
2-way proportional valves 2-10 Vdc 2
3-way proportional valve 2-10 Vdc 3
Damper actuator 2-10 Vdc 2
Fan and pump motor VFD 0-10V/4-20 mA/0-20 mA 2 wire RS485 via RJ45 3
Floating point On/Off Outputs
Device Analog signal type Quantity 3-way valves on/off 600 Ohms 3
There is a NI cRIO controller, two EtherCAT RIO chassis and 19 modules for the control
system. Table 7 shows the description of each module and Figure 39 shows the modules location.
The NI cRIO-9074 integrated system combines a real-time processor and a reconfigurable field-
programmable gate array (FPGA) within the same chassis for embedded machine control and
monitoring applications. The EtherCAT RIO is an expansion chassis and can provide high speed
I/O and control applications.
47
Table 7 Control Modules Specification
Figure 39 NI Control Modules
The power connection for the chiller and heater come from one power box in the lab. All
the cables needed in the control system were brought overhead and connected to a power
Name NO. Description Application
NI 9217 5 4-Channel, 100 Ω RTD, 24-Bit Analog Input Module Water temperature measurements
NI 9481 2 4-Channel Relay [30 VDC (2 A), 60 VDC (1 A), 250 VAC (2 A)]
3-way floating control valves
NI 9263 2 4-Channel, 100 kS/s, 16-bit, ±10 V, Analog Output Module
Control the proportional valves
NI 9422 1 8 Ch, 24 V to 60 V, 250 µs, Sinking/Sourcing Digital Input
Optional module
NI 9205 1 32-Ch ±200 mV to ±10 V, 16-Bit, 250 kS/s Analog Input Module
Indicate water flow meter and air flow stations
NI 9474 1 8-Channel 5 to 30 V, 1 µs, Sourcing Digital Output Module
Control the circulating pumps
NI 9225 4 3-Channel, 300 Vrms Analog Input Module Voltage measurements
NI 9227 3 4-Channel Current Input C Series Module Current measurements
48
enclosure which is shown in Figure 40. There are four power switches on the top panel of the
box which used for turning on the power supply for the control system. On the top of the back
panel, there are block connectors for distributing power. The orange, black and green blocks are
fuse holder for 24 VDC and 24 VAC. The lower part is all the connectors used for controlling or
receiving signals. On the cover side of the box, there are two CT coils used for current
measurement, two transformers, relays for the pumps and a NI PS-15 power supply of 5A, 24
VDC.
Figure 40 Power Distribution Unit
A computer acts as the host system for the whole HVAC system control was installed
neat the control rack as shown in Figure 41. The control modules and controllers can be
configured in Measurement and Automation Explorer (MAX) and all the control programming
was done in LabVIEW.
49
Figure 41 System Control Desk
4.2.4 Insulation for the HVAC System
One inch wide fiber glass boards were used for the indoor, outdoor and ducts insulation
(figure 42).
Figure 42 Insulation of the HVAC System
50
4.3 Software Development for Control Operation and Data Acquisition
As stated in the previous chapter, LabVIEW was used as the control interface. It is an
interactive graphic environment for modeling and simulating dynamic systems. The controller
and modules can be easily configured and programmed in LabVIEW. Routines for both data
acquisition and control purpose can also be applied graphically in LabVIEW.
There are several control tasks that were done in the project:
Project measurement and system operation monitoring
Equipment control including the chiller, air handling unit and the two simulated box for
indoor and outdoor conditions
Subsystem operations which consist of chilled water, hot water, cooling air and heating
air systems
Whole system control
The whole system control logic can be generalized as following:
System initialization/ start-up
Assign data to the setpoints and set operating conditions
Read and store data from the DAQ interface and set data filter
Calculate the room load, cooling/heating load, room load and the flow rate or temperature
needed
Change the flow rate of the HXZ to meet the design room load
Vary outdoor air and return air dampers’ position to meet the percentage of outdoor air
demand
Change the cooling/heating coil’s flow rate in the AHU to meet the supply air
temperature setpoint
51
Change the fan speed to vary the supply air flow rate and tracking the power
consumption
Calculate the outdoor air load
Change the water flow rate to meet the outdoor air load
Results generation
All the inputs of the control system are listed in Table 8. There are temperature sensors,
flow meters, air flow stations and power measurement instruments.
Table 8 System Outputs
Name Description
Tcws_HXO Chilled water supply temperature for HXO
Tcwr_HXO Chilled water return temperature for HXO
Thws_HXO Hot water supply temperature for HXO
Thwr_HXO Hot water return temperature for HXO
Thws_AHU Hot water supply temperature for AHU
Thwr_AHU Hot water return temperature for AHU
Tcws_AHU Chilled water supply temperature for AHU
Tcwr_AHU Chilled water return temperature for AHU
Thws_HXZ Hot water supply temperature for HXZ
Thwr_HXZ Hot water return temperature for HXZ
Tcws_HXZ Chilled water supply temperature for HXZ
Tcwr_HXZ Chilled water return temperature for HXZ
Thwr Hot water return temperature
Thws Hot water supply temperature
Tcwr Return chilled water temperature
Tcwr Supply chilled water temperature
Tai_HXO Inlet air temperature for HXO
52
Tao Outdoor air temperature
Tar Return air temperature
Tam Mixed air temperature
Tac Air temperature Leaving heating coil and entering cooling coil
Tas Supply air temperature
Taz Zone air temperature
Fcws_HXO Chilled water supply flow rate for HXO
Fhws_HXO Hot water supply flow rate for HXO
Fhwr_AHU Hot water return flow rate for AHU
Fcwr_AHU Chilled water return flow rate for AHU
Fhwr_HXZ Hot water supply flow rate for HXZ
Fcwr_HXZ Chilled water supply flow rate for HXZ
Fao Outdoor air flow rate
Fas Supply air flow rate
Icp Current of chiller pump
Icc Current of chiller compressor
Iwh Current of water heater
Ifm Current of VFD fan motor
Icw Current of chilled water pump
Ihw Current of hot water pump
Vcp Voltage of chiller pump
Vcc Voltage of chiller compressor
Vwh Voltage of water heater
Vfm Voltage of VFD fan motor
Vcw Voltage of chilled water pump
Vhw Voltage of hot water pump
53
4.3.1 Control System Setup in MAX and LabVIEW
With MAX, the control devices and software can be configured and updated. Figure 43
shows the window of the cRIO and EtherCAT in MAX. The left side is a tree control of the
controllers and software while the right side is the configuration of the cRIO and EtherCAT.
Figure 43 Measurement and Automation Explorer (MAX) Operation Window
In order to implement control strategies to the system, a control interface was developed.
As shown in the Figure 44, the configuration of the system was uploaded in LabVIEW. In the
project explorer window, each of the devices with its modules is shown as a tree control and all
the files included in this project are shown as well.
54
Figure 44 Controller Configurations in LabVIEW
A main operation VI was developed for the whole system which consists of system
monitoring, data logging and subsystem operation (Figure 45 and Figure 46). The system
configuration is shown in the main interface, the water and air flow rates and temperatures can be
seen on the screen and all the valves can be set to adjust the flow rates.
55
Figure 45 Main Operation VI for the Summer Condition
Figure 46 Chilled Water Storage Subsystem Operation VI
56
A system monitoring VI was developed in LabVIEW to show the values of the entire
measurement instrument. The water and air temperature and flow rates are shown in tab control
with graphs (Figure 47). The power consumption of each facility is also indicated in the front
panel.
Figure 47 Water Temperature Indicators
The data can be stored in TDMS file when running the data storage function. TDMS
means technical data management streaming which is the most common file format used by
national instruments software to store acquired data channels, and is also open to third party tool
such as excel. Figure 48 indicates a TDMS file for the water temperatures and the time.
57
Figure 48 TDMS File for Water Temperatures
58
Chapter 5
SYSTEM OPERATION AND PERFORMANCE IDENTIFICATION
5.1 Equipment and System Operation
This section lists the operation control specifications for equipment and the interactions
between them which including the measurement inputs, control outputs and equipment
initialization and alarm.
5.1.1 Chilled Subsystem Operation
Outputs and Calculations
Cooling load: (ṁCp∆T)_chiller
Power consumption: Power of Chiller Pump – (IV)_cp
Power of Chiller Compressor – (IV) _cc
Measurements
Tcws – Actual chilled water supply temperature (to process)
Tcwr – Chilled water return temperature
Fcw – Chilled water flow rate
Icp – Chiller pump current
Icc – Chiller compressor current
Vcp – Chiller pump voltage
Vcc – Chiller compressor voltage
Setpoints
Supply chilled water temperature (45⁰F to 55⁰F)
Specification
59
The chiller subsystem consists of a portable chiller, a storage tank, a displacement
chilled water pump and two 3-way control valves. The chilled water supply flow rate is
constant. The supply temperature (to process) depends upon the chilled water return
temperature from HXZ, HXO and AHU and the supply temperature set point.
Normal Operation
Set the chilled water temperature; receive Tcws_p and Tcwr from the DAQ
interface. Using PI control to maintain the constant supply chilled water temperature.
For the power consumption measurement, receive date from the current and voltage
monitor.
The cooling load was calculated using the relative equations. Figure 2 shows the
normal operation VI will be used in LabVIEW.
Thermal Storage Mode
When switch to the chilled water storage state, change the 3-way valves
position and then turn on the chiller. After the tank is charged, the chiller will be
turned off. Referring to Figure 1, the high lever limit and low lever limit can be set.
Alarm
If the high temperature deviation is more than 10 degF or low temperature
deviation is lower than 5 degF, the chiller pump will shut down. When the
circulating pump pressure is more than 250 psi, the pump will shut down.
Start-up
When the chiller receives a start-up command, the system checks the valves
position (including the thermal storage mode 3-way valve and the summer, winter
condition valves). Also, check the supply chilled water temperature. If all the valves
are in the proper position, the chilled water temperature is higher than the setpoint
60
and the circulating pump is shut down, the chiller will start; otherwise, the start-up
will halt.
Shutdown
The chiller starts to shut down when it receives the command through the
control system, or when the chiller detects an operational malfunction or component
failure. Before shutting down the chiller, turn off the circulating pump if it is in use.
5.1.2 Hot Water Subsystem Operation
Outputs
The data will plot on the screen and be stored in excel sheet every 10 seconds.
Heating load: (ṁCp∆T)_heater
Power consumption: Power of heater – (IV)_h
Measurements
The data will plot on the screen and be stored in excel sheet every 10 seconds.
Thws – Hot water supply temperature (to process)
Thwr – Hot water return temperature
Fhw – Hot water flow rate
Ih – Heater current
Vh– Heater voltage
Setpoints
Heat elements ON/OFF
Specification
The water heater subsystem consists of a hot water heater and a circulating water
pump. The hot water supply temperature (Thws) depends on the hot water return
61
temperature (Thwr) and the power applied to the heater (Pwh). There is thermostat can be
adjust manually to set the hot water supply temperature (Thws). The hot water flow rate
discharged from the water heater is the sum of Fhwr_HXZ and Fhws_HXO in summer
condition and Fhwr_AHU in winter condition.
Normal Operation
Start the hot water heater; receive the supply water temperature and flow rate
from DAQ interface. The heating load and power consumption will be calculated
using the relative equations above. Figure $ shows the normal operation and alarm
VI.
Alarm
When the hot water supply temperature is higher than the setpoint, the
heating elements will shut down to prevent overheating. If the circulating pump
pressure is higher than 250 psi, the pump will shut down.
Start-up
When the electrical heater receives a start-up command, the system checks
the valves position (including the summer, winter condition valves) and the supply
temperature. If all the valves are in the proper position, the supply temperature is
lower than the setpoint and the circulating pump is shut down, the electrical heater
will start; otherwise, the start-up will halt.
Shutdown
The electrical heater starts to shut down when it receives the command
through the control system, or when the heater detects an operational malfunction or
component failure. Before shutting down the heater, make sure the hot water
circulating pump is turned off.
62
5.1.3 Air Handler Unit Operation
Outputs
The data will plot on the screen and be stored in excel sheet every 10 seconds.
Cooling/Heating air load: Sensible-1.08 q dt
Latent-4,840 q dwlb
Power consumption: Power of VFD fan – (IV)_fan
Measurements
The data will plot on the screen and be stored in excel sheet every 10 seconds.
Fas – Air supply flow rate
Pas – Supply air pressure
Fao – Outdoor air supply flow rate
Tam – Mixed air temperature
Tas – Supply air temperature
Tar – Return air temperature
Tao – Outdoor air temperature
Has – Supply air humidity
Hao – Outdoor air humidity
Setpoints
Supply air temperature (Taz)
VFD fan speed Cfs
Outdoor air damper position Cdo
Return air damper position Cdr
Specification
63
The variable frequency drive (VFD) allows the centrifugal fan to change its speed,
varying the air flow rate goes through the system. Design air flow is 400 cfm. The
relationship of the flow rate and fan speed will be determined by experimental tests.
Constant Air Volume (CAV) Operation
The speed of the fan is constant during operation. Supply air temperature can
only be adjusted by the water subsystem. The water flow rate in the heating/cooling
coil is related to the zone temperature setpoint. Set the speed of the VFD and turn on
the fan. Receive data of the air flow rate. The power will be calculated and stored
for future use.
Variable Air Volume (VAV) Operation
By using VAV system, the air load can be changed by both the air flow rate
and temperature. Turn on the fan and vary the speed of the VFD to see the change of
the air flow rate according to the zone air temperature setpoint. Calculate and store
the power consumption data.
Two dampers are used for external and return air ducts. The dampers are
ganged together within the controller so as to collectively maintain a constant
opening area. This allowed the dampers to vary the mix of external and return air
with only small variations in the air flow rate. Use the experimental data to find the
relationship between the voltage and the damper position. Establish the damper
control equations used for the three operation conditions:
No Outdoor Air Operation
100% Outdoor Air Operation
Certain Amount of Outdoor Air Operation
64
Normal Operation
Set the zone air temperature and the amount of outdoor air. Collecting data
from the DAQ interface and monitoring the power consumption of the VFD fan.
Change the fan speed and the amount of outdoor air depending on the variation of
zone load.
Alarm
If the pressure of the fan outlet is higher than, the fan will switched off.
Start-up
When the AHU receives the start-up command, the AHU will read all inputs to
determine the initial values. Also, the damper position will be checked and then the
fan will be turned on.
Shutdown
The AHU starts to shut down when it receives the command through the control
system, or when the AHU detects an operational malfunction or component failure.
5.1.4 AHU Cooling/Heating Coil Subsystem Operation
Outputs
The data will plot on the screen and be stored in excel sheet every 10 seconds.
Cooling coil load: (ṁCp∆T)_AHUcc
Heating coil load: (ṁCp∆T)_AHUhc
Measurements
The data will plot on the screen and be stored in excel sheet every 10 seconds.
Thws_AHU – Hot water supply temperature sensor for AHU
Thwr_AHU – Hot water return temperature sensor for AHU
Tcws_AHU – Chilled water supply temperature sensor for AHU
65
Tcwr_AHU – Chilled water return temperature sensor for AHU
Fhwr_AHU – Hot water return meter for AHU
Fcwr_AHU – Chilled water return meter for AHU
Fas – Supply air flow rate
Tas – Supply air temperature
Specification
The AHU cooling/heating coil subsystem includes two coils and two control
valves. The flow rate goes through each coil will be controlled by 3-way control valves.
The heat energy transfer depends upon the physical properties of the heat exchanger and
is a function of the temperatures and flow rates of the air and water.
Normal operation
The flow rates goes into the coils is controlled by the valve position. When the
control valve receives a command, it will open or close depending on the signal. The
relationship between the voltage signal and the flow rate will be determined using
experiment tests data. Figure 7 shows the coiling/heating coil operation.
5.1.5 HXZ and HXO Subsystem Operation
Measurements
Tcws_HXO – Chilled water supply temperature sensor for HXO
Tcwr_HXO – Chilled water return temperature sensor for HXO
Thws_HXO – Hot water supply temperature sensor for HXO
Thwr_HXO – Hot water return temperature sensor for HXO
Thws_HXZ – Hot water supply temperature sensor for HXZ
Thwr_HXZ – Hot water return temperature sensor for HXZ
Tcws_HXZ – Chilled water supply temperature sensor for HXZ
AO Signal
66
Tcwr_HXZ – Chilled water return temperature sensor for HXZ
Fcws_HXO – Chilled water supply meter for HXO
Fhws_HXO – Hot water supply meter for HXO
Fhwr_HXZ – Hot water supply meter for HXZ
Fcwr_HXZ – Chilled water supply meter for HXZ
Fao – Outdoor air flow rate
Fas – Supply air flow rate
Setpoints
Tao – Outdoor air temperature
Taz – Zone air temperature
Specification
Three types of valves are used in this system to control the water flow rate or direction.
Two-way Proportional Control Valve
Three-way Bypass Valve
Three-way On/Off Valve
The water temperature will be controlled by the chiller and the heater; the water rates
depend upon the air temperature desired and the air flow rate. HXZ is used to simulate the room
load and the HXO to simulate the outdoor air temperature.
The whole system operation logic was built after the development of the equipment and
subsystem control logic, which includes summer and winter operation.
67
5.2 System Performance Identification
After the development of the system operation logic, the system performance should be
tested prior of any experiments. A serial of tests will be conducted to check the system
functionality and energy balance.
System initialization is very important to protect the equipment and system. The
followings are the steps should be done:
Turn on the power switches of the equipment and enclosure box
Open the operation VI in LabVIEW and set the outputs needed for the specific state
Check if the control valves are in the proper position or not
5.2.1 Steady State Verification
In order to verify the system’s stability, both the summer and winter conditions were run
for enough periods of time and the data were collected in excel file. Besides, in these operations,
the control valves are fully open or fully closed, which means there was no control of the system.
Figure 49 indicates the supply hot and chilled water temperatures which were set to
120 °F and 50 °F. After one hour of operation, the hot water temperature remains 123 °F to
125 °F and the chilled water temperature remains 50 °F.
68
Figure 49 Supply Water Temperatures
The water flow rates of the air handler unit (AHU), the outdoor heat exchanger (HXO)
and the indoor heat exchanger (HXZ) are shown in Figure 50. There are 0.05 gpm variations in
the flow rates which due to the differences between the time constant of the flow meter and the
data storage speed of the program. Besides, the variations are within the flow meters’ accuracy
which is 0.09 gpm.
Figure 50 Water Flow Rates
0
20
40
60
80
100
120
140
0 1000 2000 3000 4000
Tem
per
atu
re (
°F)
Time (Sec)
Supply Water Temperatures
1S CHILLER 2S HEATER
1.5
1.7
1.9
2.1
2.3
2.5
0 500 1000 1500 2000 2500 3000 3500 4000
Flo
w R
ate
(GP
M)
Time (Sec)
Water Flow Rates
FM.1. AHU (GPM) FM.2.HXO (GPM) FM.2. HXZ (GPM)
69
There are five air temperatures can be measured in the system: 402. Figure 51 indicates
the steady air temperatures. The simulated outdoor air temperature can go up to 102 °F and the
zone air temperature stays at 68 °F. While the supply air temperature is 66 °F, the return air
temperature is 70 °F and the mixing air temperature is 80 °F.
Figure 51 Air Temperatures
The air flow rates which can be seen from Figure 52 are stable in ± 20cfm. In this
operation, the return damper is fully open and the outdoor damper is 20% open. The sum of
return and outdoor air flow rates are less than the supply for about 20 cfm, which is in the
accuracy of the air flow station measurements.
50
60
70
80
90
100
110
0 500 1000 1500 2000 2500 3000 3500 4000
Tem
per
atu
re (
F)
Time (Sec)
Air Temperatures Supply Air (F) Return Air (F) Outdoor Air (F) Mixing Air (F) Zone Air (F)
70
Figure 52 Air Flow Rates
5.2.2 Energy Balance Identification
In order to check the energy balance of the components and the whole system, load
calculations were conducted for the heat exchangers in the outdoor box, indoor box and the air
handler unit. The test conditions in these calculations are shown in Table 9 and Table 10.
Table 9 Test Conditions - Summer
Root Name Title Author Date/Time Groups
Operation Data Summer Operation Li Cui 12-12-2012 01:29:50 PM 8
Group Channels Time 1
Description
HXO 3
VFD 5V (50%)
AHU 3
VFD Speed 918 rpm
HXZ 3
Damper R 8.5V (100%)
HEATER 2
Damper O 6.5V (70%)
CHILL 1
Chiller Set Point 50F
Air 5 AF 3
0
50
100
150
200
250
300
350
400
450
0 500 1000 1500 2000 2500 3000 3500 4000
Flo
w R
ate
(CFM
)
Time (Sec)
Air Flow Rates AF.O.F (CFM) AF.R.F (CFM) AF.S.F (CFM)
71
Table 10 Test Conditions - Winter
Root Name Title Author Date/Time Groups
Operation Data Winter Operation Li Cui 12-12-2012 02:39:34 PM 8
Group Channels
Time 1
Description
HXO 3
VFD 5V (50%)
AHU 3
VFD Speed 918 rpm
HXZ 3
Damper R 8.5V (100%)
HEATER 2
Damper O 6.5V (70%)
CHILL 1
Chiller Set Point 50F
Air 5
AF 3
5.2.2.1 Outdoor Air Simulation Box
Table 11 shows the sample data and the load calculations of the outdoor box in summer
condition. The average values are listed in bold in the last row of the table. From the results the
water load is 685 Btu/hr larger than the air side, which may due to the uncertainty of the air flow
rate measurements and the small water temperature differences.
Table 11 Outdoor Simulation Heat Exchanger Load Calculations – Summer (Heating)
Outdoor Water Side
2I HXO (F)
2O HXO (F)
FM.2.HXO (GPM)
T_dif_w_HXO (F)
FM.2.HXO (lb/hr)
Qw_HXO (BTU/hr) 10 Sample
120.071 117.795 2.015 2.277 1008.556 2296.041
120.108 117.772 2.011 2.336 1006.420 2350.775
120.087 117.854 2.008 2.233 1005.023 2243.865
120.117 117.862 2.020 2.255 1010.939 2279.846
120.105 117.832 2.010 2.273 1006.256 2287.459
120.007 117.495 2.022 2.513 1012.254 2543.583
120.132 117.756 2.018 2.376 1010.282 2400.523
120.164 117.839 2.009 2.325 1005.516 2337.506
120.151 117.855 2.025 2.296 1013.487 2327.015
120.158 117.802 2.016 2.356 1009.132 2377.044 2344.366
… … … … … … …
121.196 118.894 2.043 2.302 1022.73 2354.568
72
Outdoor Air Side
T_lab (F)
Outdoor Air (F)
AF.O.F (CFM)
T_dif_a_HXO (F)
AF.O.F (lb/hr)
Qa_HXO (BTU/hr) 10 Sample
79.79 97.327 135.833 17.537 610.327 2568.743
79.79 97.427 135.734 17.637 609.885 2581.586
79.79 97.439 135.784 17.649 610.106 2584.253
79.79 97.510 135.652 17.720 609.516 2592.127
79.79 97.681 136.178 17.891 611.876 2627.332
79.79 98.012 136.621 18.222 613.868 2684.639
79.79 98.130 137.163 18.340 616.302 2712.766
79.79 98.272 137.622 18.482 618.367 2742.905
79.79 98.449 137.934 18.659 619.768 2775.492
79.79 98.455 137.918 18.665 619.695 2776.040 2664.588
… … … … … … …
79.79 100.209 138.011 20.419 620.115 3040.371 3040.117
The winter load calculations are indicated in Table 12. The average values are listed in
bold in the last row of the table. From the results the water load is 1183 Btu/hr larger than the air
side, which may due to the uncertainty of the air flow rate measurements and the small water
temperature differences. The heat exchange in summer is much better than it in winter condition.
The reason may be the water also absorbs heat from the ambient environment such as the metal of
the outdoor box.
Table 12 Outdoor Simulation Heat Exchanger Load Calculations – Winter (Cooling)
Outdoor Water Side
2I HXO (F)
2O HXO (F)
FM.2.HXO (GPM)
T_dif_w_HXO (F)
FM.2.HXO (lb/hr)
Qw_HXO (BTU/hr) 10 Sample
52.021 53.827 2.030 1.806 1015.952 1834.729
51.988 53.782 2.041 1.794 1021.622 1832.358
51.897 53.698 2.029 1.800 1015.459 1828.264
51.870 53.686 2.031 1.816 1016.856 1846.958
51.864 53.639 2.018 1.776 1010.118 1793.764
51.792 53.586 2.030 1.794 1016.198 1823.523
51.702 53.512 2.038 1.810 1020.389 1846.871
51.667 53.476 2.033 1.809 1017.431 1840.550
51.629 53.445 2.034 1.816 1018.171 1848.780
73
51.641 53.401 2.037 1.761 1019.567 1795.277 1829.107
… … … … … … …
50.850 52.475 2.054 1.625 1028.404 1671.129 1671.053
Outdoor Air Side
T_lab (F)
Outdoor Air (F)
AF.O.F (CFM)
T_dif_a_HXO (F)
AF.O.F (lb/hr)
Qa_HXO (BTU/hr) 10 Sample
79.79 60.445 112.769 19.345 506.697 2352.482
79.79 60.392 112.769 19.398 506.697 2358.950
79.79 60.398 112.441 19.392 505.222 2351.366
79.79 60.362 111.883 19.428 502.714 2343.972
79.79 60.362 111.768 19.428 502.198 2341.565
79.79 60.321 111.965 19.469 503.083 2350.686
79.79 60.321 111.620 19.469 501.534 2343.449
79.79 60.226 111.555 19.564 501.239 2353.445
79.79 60.197 111.883 19.593 502.714 2363.936
79.79 60.055 111.801 19.735 502.345 2379.301 2353.915
… … … … … … …
79.79 56.108 111.829 23.682 502.473 2854.312 2854.187
5.2.2.2 Indoor Condition Simulation Box
The sample data and load calculations for the indoor simulation box of the summer
condition are shown in Table 13. The water side heat exchange is 861 Btu/hr larger than the air
side, which may due to the heat exchanger efficiency and the sensor uncertainty.
Table 13 Indoor Simulation Heat Exchanger Load Calculations – Summer (Heating)
Indoor Water Side
2I HXZ (F)
2O HXZ (F)
FM.2. HXZ (GPM)
T_dif_w_HXZ (F)
FM.2.HXZ (lb/hr)
Qw_HXZ (BTU/hr) 10 Sample
120.123 117.915 1.951 2.208 976.838 2156.905
120.117 117.943 1.946 2.174 974.373 2118.384
120.117 117.957 1.929 2.160 965.663 2086.018
120.113 117.966 1.946 2.146 974.044 2090.569
120.116 117.975 1.941 2.140 971.661 2079.786
120.120 117.987 1.954 2.133 977.906 2086.093
120.123 117.991 1.948 2.132 975.359 2079.309
120.130 117.992 1.945 2.138 973.387 2080.806
120.140 117.995 1.950 2.145 976.345 2094.486
74
120.147 118.000 1.945 2.147 973.387 2089.510 2096.187
… … … … … … …
121.259 119.201 1.977 2.058 989.467 2035.865 2035.916
Indoor Air Side
Supply Air (F)
Return Air (F)
AF.S.F (CFM)
T_dif_a_HXZ(F)
AF.S.F (lb/hr)
Qa_HXZ (BTU/hr) 10 Sample
66.839 69.564 414.782 2.724 1863.707 1218.554
66.863 69.540 414.656 2.677 1863.139 1197.043
66.940 69.552 415.478 2.612 1866.836 1170.293
66.975 69.552 416.776 2.577 1872.666 1158.012
67.212 69.776 417.567 2.565 1876.222 1154.889
67.448 70.013 418.707 2.565 1881.341 1158.040
67.672 70.190 419.941 2.517 1886.887 1140.044
67.879 70.308 421.239 2.429 1892.717 1103.301
67.856 70.456 421.239 2.600 1892.717 1181.149
67.891 70.521 421.112 2.630 1892.149 1194.212 1167.554
… … … … … … …
67.422 70.035 416.864 2.613 1873.062 1174.833 1174.857
The winter load calculations are indicated in Table 14. The average values are listed in
bold in the last row of the table. From the results the water load is 1201 Btu/hr larger than the air
side, which may due to the uncertainty of the air flow rate measurements and the small water
temperature differences. The heat exchange in summer is much better than it in winter condition.
The reason may be the water also absorbs heat from the ambient environment such as the metal of
the indoor box.
Table 14 Indoor Simulation Heat Exchanger Load Calculations – Winter (Cooling)
Indoor Water Side
2I HXZ (F)
2O HXZ (F)
FM.2. HXZ (GPM)
T_dif_w_HXZ(F)
FM.2.HXZ (lb/hr)
Qw_HXZ (BTU/hr) 10 Sample
51.424 52.971 2.009 1.547 1005.680 1555.655
51.383 52.917 2.011 1.534 1006.420 1543.754
51.299 52.808 2.017 1.510 1009.871 1524.538
51.259 52.755 2.016 1.497 1009.049 1510.220
51.218 52.701 2.012 1.483 1007.406 1494.148
51.178 52.650 2.005 1.472 1003.544 1477.073
75
51.098 52.548 2.014 1.450 1008.392 1462.238
51.056 52.501 2.025 1.445 1013.815 1465.064
51.015 52.455 2.027 1.440 1014.719 1461.047
50.977 52.407 2.012 1.430 1007.406 1440.515 1493.425
… … … … … … …
50.065 50.741 1.988 0.676 995.196 672.704 672.792
Indoor Air Side
Supply Air (F)
Return Air (F)
AF.S.F (CFM)
T_dif_a_HXZ (F)
AF.S.F (lb/hr)
Qa_HXZ (BTU/hr) 10 Sample
92.599 85.537 406.079 7.062 1824.601 3092.445
92.670 85.537 405.857 7.133 1823.605 3121.795
92.564 85.502 405.572 7.062 1822.326 3088.589
92.652 85.555 405.857 7.097 1823.605 3106.277
92.605 85.490 405.667 7.115 1822.752 3112.579
92.717 85.543 405.731 7.174 1823.037 3138.921
92.711 85.531 405.636 7.180 1822.610 3140.771
92.776 85.561 406.300 7.216 1825.596 3161.453
92.670 85.643 405.857 7.026 1823.605 3075.240
92.540 85.543 404.528 6.997 1817.633 3052.278 3109.035
… … … … … … …
96.684 92.559 421.604 4.125 1894.360 1872.710 1874.077
5.2.2.3 Air Handler Unit
Table 15 shows the sample data and the load calculations of the air handler unit in
summer condition. The average values are listed in bold in the last row of the table. The air side
heat exchange is 93% of the water side which is the best heat exchange rate of the three heat
exchangers. The temperatures before and after the fan were 64.5 °F and 67.3 °F which means the
heat increase across the fan was 1259 Btu/hr.
Table 15 AHU Heat Exchanger Load Calculations – Summer (Cooling)
AHU Water Side
1I AHU (F)
1O AHU (F)
FM.1. AHU (GPM)
T_dif_w_AHU(F)
FM.2.AHU (lb/hr)
Qw_AHU (BTU/hr) 10 Sample
59.716 65.529 1.910 5.813 956.131 5558.413
59.695 65.548 1.918 5.852 959.911 5617.686
76
59.717 65.550 1.904 5.833 953.172 5559.875
59.744 65.557 1.892 5.813 947.174 5505.846
59.763 65.557 1.907 5.793 954.734 5531.118
59.734 65.549 1.903 5.815 952.762 5539.894
59.683 65.546 1.903 5.863 952.679 5585.862
59.609 65.546 1.914 5.937 958.103 5688.390
59.527 65.549 1.900 6.022 951.118 5727.353
59.456 65.546 1.888 6.090 945.284 5756.791 5607.123
… … … … … … …
58.852 64.968 1.940 6.115 971.345 5939.941 5939.722
AHU Air Side
Mixing Air (F)
Supply Air (F)
AF.S.F (CFM)
T_dif_a_AHU (F)
AF.S.F (lb/hr)
Qa_AHU (BTU/hr) 10 Sample
78.948 66.839 414.782 12.109 1863.707 5416.078
78.967 66.863 414.656 12.104 1863.139 5412.384
78.975 66.940 415.478 12.035 1866.836 5392.296
78.975 66.975 416.776 12.000 1872.666 5393.201
78.976 67.212 417.567 11.765 1876.222 5297.621
78.990 67.448 418.707 11.542 1881.341 5211.585
78.987 67.672 419.941 11.315 1886.887 5123.877
78.991 67.879 421.239 11.112 1892.717 5047.638
78.989 67.856 421.239 11.133 1892.717 5057.372
78.989 67.891 421.112 11.097 1892.149 5039.499 5239.155
… … … … … … …
79.762 67.422 416.864 12.340 1873.062 5545.120 5544.619
The winter condition for the air handler unit load calculation is shown in Table 16. The
water side heat exchange is 2634.6 Btu/hr less than the air side. The temperature difference
before and after the fan were 98 °F and 95.7 °F, which made 1045.687 Btu/hr heat loss.
Table 16 AHU Heat Exchanger Load Calculations – Winter (Heating)
AHU Water Side
1I AHU (F)
1O AHU (F)
FM.1. AHU (GPM)
T_dif_w_AHU(F)
FM.2.AHU (lb/hr)
Qw_AHU (BTU/hr) 10 Sample
119.837 113.761 1.844 6.077 923.097 5609.247
119.833 113.761 1.842 6.072 922.111 5598.894
119.828 113.766 1.834 6.062 918.085 5565.255
119.826 113.773 1.833 6.053 917.756 5555.097
77
119.819 113.779 1.844 6.040 923.097 5575.618
119.817 113.779 1.840 6.038 921.043 5561.160
119.814 113.777 1.838 6.037 920.139 5554.421
119.814 113.775 1.841 6.039 921.618 5565.655
119.812 113.768 1.837 6.044 919.318 5556.613
119.808 113.760 1.833 6.048 917.592 5549.750 5569.171
… … … … … … …
119.538 113.616 1.850 5.922 925.899 5483.185 5486.391
AHU Air Side
Mixing Air (F)
Supply Air (F)
AF.S.F (CFM)
T_dif_a_AHU (F)
AF.S.F (lb/hr)
Qa_AHU (BTU/hr) 10 Sample
75.786 92.599 406.079 16.813 1824.601 7362.373
75.785 92.670 405.857 16.885 1823.605 7389.877
75.798 92.564 405.572 16.766 1822.326 7332.610
75.791 92.652 405.857 16.861 1823.605 7379.579
75.793 92.605 405.667 16.812 1822.752 7354.719
75.785 92.717 405.731 16.932 1823.037 7408.378
75.772 92.711 405.636 16.939 1822.610 7409.619
75.760 92.776 406.300 17.016 1825.596 7455.446
75.750 92.670 405.857 16.920 1823.605 7405.356
75.748 92.540 404.528 16.792 1817.633 7324.990 7382.295
… … … … … … …
78.829 96.684 421.604 17.855 1894.360 8120.275 8120.986
5.2.2.4 Overall System Energy Balance With and Without Outdoor Air
The system energy balance of the air side was verified after the calculation of each heat
exchanger. Table 17 shows the air side balance check results, which indicates that the energy
balance of the system with and without outdoor air.
Table 17 Overall System Energy Balance
HXO (Btu/hr)
AHU (Btu/hr)
HXZ (Btu/hr)
Fan (Btu/hr)
Sum (Btu/hr) Difference
With OA Summer 3040.371 -5545.120 1174.833 1258.698 -71.218 1.30%
With OA Winter -2854.312 8120.275 -1872.710 -1045.687 2347.573 33.8%
Without OA 0 -2058.47 1358.8 826.66 126.99 5.98%
78
5.3 Characteristics of the System Components
In order to develop the control logic for the system, the characteristics of relative
components, which are the chiller, coils, dampers, control valves and the fan with VFD, should be
determined first. In this thesis, only the control valves of the outdoor and indoor boxes are tested
due to the time limitation.
5.3.1 Outdoor Box
The simulated outdoor air temperature in summer condition can reach 103 °F and can be
as low as 54 °F in winter condition. Figure 53 indicates the flow characteristic of the outdoor hot
water control valve, which is fitted to linear pattern. That is to say the flow capacity increases
linearly with valve travel, which can be used to modeling the control valve.
Figure 53 Installed Valve Characteristics for HXO Hot Water
Figure 54 indicate the installed valve characteristics for HXO chill, which is suited for
quick open characteristic. The valve provides large flow changes in a small percentage of valve
travel.
0
0.5
1
1.5
2
2.5
3
3.5
0% 20% 40% 60% 80% 100%
Flo
w R
ate
(gp
m)
% Open
Installed Valve Characteristic for HXO Hot Water
Measured
Linear Trendline
79
Figure 54 Installed Valve Characteristic for HXO Chill
After determined the valve characteristic, control logics can be programmed and applied
on the valve. PID control was the simplest and easiest control strategy that can be tested first.
Figure 55 shows the open loop tuning process of the hot water valve.
1. Develop the PID control logic in LabVIEW using the PID control tool box
2. Set the controller in manual mode and the valve is fully close
3. Make a step change in output from 2v to 8v
4. Wait until the process variable to settle and record the process in excel
5. Determine the parameters will be used in the PID control:
Td – Deadtime in minutes = 1.33
T – Time constant in minutes = 3.67
K - Process Gain =
= 1.71
6. Calculate the PID value
0
0.5
1
1.5
2
2.5
0% 20% 40% 60% 80% 100%
Flo
w R
ate
(gp
m)
% Open
Installed Valve Characteristic for HXO Chill
Flow Rate (gpm)
Poly. 3 Trendline
80
PB =
= 49.58
Reset = 2.00 Td = 2.66
Rate = 0.50 Td = 0.665
Figure 55 Output and Process Variable Chart
5.3.2 Indoor Box
The flow characteristic for the indoor hot water control valve is shown in Figure 55. It
can be treated as equal percentage pattern, which the flow rate increases exponentially with valve
trim travel. Besides, equal increments of valve travel produce equal percentage changes in the Cv,
which is 1.2 for this valve.
81
Figure 56 Installed Valve Characteristic for HXZ Hot Water
Figure 56 indicate the installed valve characteristics for HXZ chill, which is suited for
quick open characteristic. The valve provides large flow changes in a small percentage of valve
travel.
Figure 57 Installed Valve Characteristic for HXZ Chill
0
0.5
1
1.5
2
2.5
3
3.5
0% 20% 40% 60% 80% 100%
Flo
w R
ate
(gp
m)
% Open
Installed Valve Characteristic for HXZ Hot Water
Flow Rate (gpm)
0
0.5
1
1.5
2
2.5
0% 20% 40% 60% 80% 100%
Flo
w R
ate
(gp
m)
% Open
Installed Valve Characteristic for HXZ Chill
Flow Rate (gpm)
Poly. 3 Trendline
82
Chapter 6
ANALYSIS AND DISCUSSION
The experimental HVAC system construction, performance identification and
components characteristics were indicated in chapter 4 and 5. This chapter will evaluate the
capability and limitation of the experimental HVAC system and discuss the system performance.
6.1 Experimental HVAC System Design vs. Actual Operation
The system has the capability of perform summer and winter operations as described in
the objectives and it can reach a steady state after certain minutes of running. The overall energy
balance of the air side in summer condition is within 2%, however the subsystem heat exchangers
load balances are not as good as expected. There could be several reasons that cause the
differences between the water side load and the air side load:
The facilities efficiency is not as good as expected
The uncertainties of the system sensors, for example, the water temperature
differences across the heat exchangers are too close to be identified.
Heat loss and heat gain through the ambient environment
The latent load is not calculated during those tests
The designed outdoor air temperature in winter is 47.6 °F but the actual temperature can
only reach 54 °F. The reason for the difference may due to the size of the heat exchanger
efficiency and/or the heat loss through the ambient air.
6.2 Measurement Uncertainty and Sensor Calibration
Since there are lots of sensors in this system, the calibration of each sensor is very
important. As is known, air flow rate is more difficult to measure than the water flow rate, which
83
due to the uncertainty of the air distribution in the ducts. In this thesis, the air flow stations were
calibrated using an anemometer and multiple tests were conducted to ensure the calibration
results. The water temperature RTD supposed to be the most reliable sensors in the project but it
turned out that the sensor is more easily to damage from the cable and the RTD module used to
record the values should be wired carefully in the right position.
6.3 System Control Capability
The control facilities of this experimental system are working properly and have the
ability of certain amount of control. The flow characteristics of the indoor and outdoor box
control valves provide good fits to standard control valve flow characteristic, such as linear, equal
percentage and quick open. However, the control valves of the air handler unit are floating valves
which have less control capabilities and need more effort to develop the control logics. Besides,
the circulating pumps of the systems are displacement pumps, which use bypass valves to adjust
the flow through each heat exchanger. This means less control capabilities compare to the
centrifugal pumps. The other limitation caused by the displacement pumps is the relationship
between the water flow rates in the same loop, for example, if reduce the flow rate in the outdoor
heat exchanger, the indoor flow rate will increase.
84
Chapter 7
CONTRIBUTIONS AND RECOMMENDATIONS
7.1 Contribution to HVAC Control Test Facility
There are several HVAC control test beds in the United States but few of them have both
simulated indoor and outdoor air chambers, which make it more flexible for the amount of
outdoor air variations and the indoor load simulations. Besides, the experimental system has
chilled water storage capability which can model thermal storage for commercial buildings.
The integrated software environment built in LabVIEW for data acquisition, system
operation and control development is another significant improvement. All the control models are
compatible with LabVIEW and easily to configured and monitored.
7.2 Future Work Recommendations
In addition to the achievements in this thesis, there are still opportunities for further
system performance improvement and control development.
There are humidity sensors can be used to measure the humidity of the simulated outdoor
air and the supply air. Besides, the power measurement suit allows energy audit of the main
facilities such as the chiller, heater, fan VFD and dampers. These data can be applied to improve
system energy savings.
More tests should be conducted under different load situations and the energy balance can
be identified after each test. This will provide plenty of information for indicating the heat
exchange across the coils in each chamber.
System simulation and modeling can be conducted. The characteristics of components
such as the damper and VFD are important for component modeling and simulation. After the
85
simulation of overall system, the performances of simulated system and the actual system can be
compared. In addition, the methodology of HVAC system simulation and modeling can be
indicated using the simulated and actual data.
86
Appendix
LABVIEW PROGRAMMING
Figure 58 Data Logging Main VI
Figure 59 Chilled Water Storage Control VI
87
Figure 60 System Monitor VI
88
Figure 61 Summer Operation Main VI
89
Figure 62 Summer Monitor VI
90
Figure 63 Winter Operation VI
91
REFERENCES
Ahn, B.-C., and Song, J.-Y. (2010). “Control characteristics and heating performance analysis of
automatic thermostatic valves for radiant slab heating system in residential apartments.”
Energy, 35(4), 1615-1624.
Anderson, M. L. (2001). “MIMO ROBUST CONTROL FOR HEATING VENTILATING
ANDAIR CONDITIONING (HVAC) SYSTEMS.”
Anderson, M., Buehner, M., Young, P., Hittle, D., Anderson, C., Tu, J., and Hodgson, D. (2007).
“An experimental system for advanced heating, ventilating and air conditioning (HVAC)
control.” Energy and Buildings, 39(2), 136-147.
ASHRAE. (1996). Reference Guide fot Dynamic Models of HVAC Equipment.
ASHRAE. (2009). Fundimentals.
Babuška, R., and Verbruggen, H. B. (1996). “An overview of fuzzy modeling for control.”
Control Engineering Practice, 4(11), 1593-1606.
BEEL at SU. (2010). “BUILDING ENERGY AND ENVIRONMENTAL SYSTEMS
LABORATORY (BEESL).” <http://beesl.syr.edu/facilities.htm> (Dec. 3, 2011).
Bing Dong. (2010). “Non-linear optimal controller design for building HVAC systems.” 2010
IEEE International Conference on Control Applications (CCA), IEEE, 210-215.
Clarke, J. ., Cockroft, J., Conner, S., Hand, J. ., Kelly, N. ., Moore, R., O’Brien, T., and Strachan,
P. (2002). “Simulation-assisted control in building energy management systems.” Energy
and Buildings, 34(9), 933-940.
“EnergyPlus: Energy simulation program.” (2000). ASHRAE Journal, 42(4), 49.
Harrold, M. V., and Lush, D. M. (1988). “Automatic controls in building services.” Electric
Power Applications, IEE Proceedings B, 135(3), 105-133.
92
House, J. M., and Smith, T. F. (1995). “Optimal control of building and HVAC systems.”
American Control Conference, 1995. Proceedings of the, IEEE, 4326-4330 vol.6.
Iowa Energy Center. (2010). Iowa Energy Center Energy Resource Station Technical Description.
Komareji, M., Stoustrup, J., Rasmussen, H., Bidstrup, N., Svendsen, P., and Nielsen, F. (2008).
“Optimal model-based control in HVAC systems.” 2008 American Control Conference
(ACC ’08), 11-13 June 2008, 2008 American Control Conference (ACC ’08), IEEE,
Piscataway, NJ, USA, 1443-8.
Komareji, M., Stoustrup, J., Rasmussen, H., Bidstrup, N., Svendsen, P., and Nielsen, F. (2009).
“Simplified optimal control in HVAC systems.” 2009 IEEE International Conference on
Control Applications (CCA), 8-10 July 2009, 2009 IEEE International Conference on
Control Applications (CCA), IEEE, Piscataway, NJ, USA, 1033-8.
LBNL. (2011). “Modelica Buildings Library.”
<http://simulationresearch.lbl.gov/modelica/FrontPage> (Dec. 9, 2011).
Liew, Y.-L. (2003). “Remote control of heating, ventilating, and air conditioning system with
LabVIEW - OpenThesis.” <http://www.openthesis.org/documents/Remote-control-
heating-ventilating-air-118524.html> (Dec. 2, 2011).
McDowall, R. (2009). Fundamentals of HVAC Control Systems. Elsevier.
Ming-Li Chiang, and Li-Chen Fu. (2006). “Adaptive and Robust Control for Nonlinear HVAC
System.” IEEE International Conference on Systems, Man and Cybernetics, 2006.
SMC ’06, IEEE, 4982-4987.
Mirinejad, H., Sadati, S. H., Ghasemian, M., and Torab, H. (2008). “Control Techniques in
Heating, Ventilating and Air Conditioning (HVAC) Systems.” Journal of Computer
Sciences, J. Comput. Sci. (USA), 4(9), 777-83.
Nizet, J. L., Lecomte, J., and Litt, F. X. (1984). Optimal control applied to air conditioning in
buildings.
93
Platt, G., Li, J., Li, R., Poulton, G., James, G., and Wall, J. (2010). “Adaptive HVAC zone
modeling for sustainable buildings.” Energy and Buildings, 42(4), 412-421.
van Schijndel, A. W. M. (2003). “Advanced HVAC modeling with FemLab/Simulink/MatLab.”
Building Services Engineering Research & Technology, Build. Serv. Eng. Res. Technol.
(UK), 24(4), 289-300.
Semsar, E., Yazdanpanah, M. J., and Lucas, C. (2003). “Nonlinear control and disturbance
decoupling of an HVAC system via feedback linearization and back-stepping.”
Proceedings of 2003 IEEE Conference on Control Applications, 2003. CCA 2003, IEEE,
646- 650 vol.1.
Singh, J., Singh, N., and Sharma, J. K. (2006). “Fuzzy modeling and control of HVAC systems -
a review.” Journal of Scientific and Industrial Research, J. Sci. Ind. Res. (India), 65(6),
470-6.
Swanson, K. (1993). “Direct Digital Control- A Tool for Energy Management of HVAC Systems.”
Ya-Gang Wang, Zhi-Gang Shi, and Wen-Jian Cai. (2001). “PID autotuner and its application in
HVAC systems.” American Control Conference, 2001. Proceedings of the 2001, IEEE,
2192-2196 vol.3.
Ying, H., Siler, W., and Buckley, J. J. (1990). “Fuzzy control theory: A nonlinear case.”
Automatica, 26(3), 513-520.
