Science and Technolgy Complex

8/3/2019 Science and Technolgy Complex

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4. 1 SCIENCE AND TECHNOLGY COMPLEX4.1.1. Organizational Background

Science and Technology Complex consists of Faculty of Civil Engineering,Faculty of Mechanical Engineering, Faculty of Electrical Engineering, Faculty

of Chemical Engineering, Faculty of Medicine, libraries, computer labs, labs

and server room.

The complex is using District Cooling System to cool down the building to

meet occupants comfort. The complex consists of 5 blocks and 2 towers with

height of 20 levels each.

4.1.2. Design SystemOverview:

Figure : TES in S&T Complex


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TABLE 3: District Cooling Design

At night (10pm-8am), Chiller absorb heat from water in Ice-cell.

During the day, (8am-11pm), ice in ice-cell absorb heat from the building,

Condenser in the chiller is cooled by cooling towers.

1. Chiller

Figure : Chiller

Specification

Made: Dunham-bush Model: WCOX128B-128B

Chiller Installed 2 x 1800 RT Base Mode

2 x 1250 RT Ice Mode

Thermal Storage Capacity 45 x 240 RTh Ice CellBuilding Cooling Load

Requirement

Block 1 550 RT

Block 2 580 RT

Block 3 380 RT

Block 4 850 RT

Block 5 660 RT

Tower 1 290 RT

Tower 2 290 RT

MaxCooling Demand 3600RT


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Compressor Type: Horizontal screw Power input (kW) : 1227 Function to make ice and cool the buildings

Capacity: 1800Rt (normal) & 1250 Rt (ice) Q uantity: 2 Chillers with 4 Compressors D esign Temp: 47.5 / 39 F (normal)

28 / 22 F (ice)

Figure : Chiller System

Basic system chiller for operation:

a. Chillersb. Pumpsc. Heat Exchangersd. Condenser Water Pumps (CWP)e. Secondary Chilled Water Pumps (SCHWP)f. Cooling Tower

There are 4 chillers for the thermal energy storage system. The chillers

tagged as Chiller 1A, 1B, 2A and 2B. There are 4 heat exchangers to transfer


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heat and reduce the pumps work. The chillers and heat exchangers are use

alternately. One will standby and the other will operate. On the next

schedule, different components will standby and operate. It will alternate

every month.

Typical Chiller Operation

In order to start a chiller the following condition must be met

a. Chilled water pump runningb. Chilled water flow switch madec. Control power switch and compressor switch ond. Circuit breaker one. All safety condition satisfiedf. Reset pressed on microcomputer keypadg. The compressor has not started within the last 20 minutesh. Leaving temperature 2F or more above setpointi. Oil sump temperature is greater than 70FThe microcomputer will start the oil pump first. If capacity indicator is below

8% and a minimum of 27 psi oil pressure is established, the microcomputer

starts the compressor motor 5 seconds later. Oil pressure and discharge are

then monitored to ensure that a different of at least 26 psi is maintained.

When the compressor starts, the microcomputer monitors leaving water

temperature, ramp schedule and load limiting to control load and unload

solenoids. The refrigerant level sensors and discharge temperature are used to

control the refrigerant modulating motor. When minimum compressor

capacity exceeds system load and water temperature fails below set point, the

compressor and oil pump will shut down.

2. Cooling Tower


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Figure : Cooling Tower

Cooling towers are heat removal devices used to transfer process waste

heat to the atmosphere. Cooling towers may either use the evaporation of

water to remove process heat and cool the working fluid to near the wet-bulb

air temperature or rely solely on air to cool the working fluid to near the dry-bulb air temperature. Common applications include cooling the circulating

water used in oil refineries, chemical plants, power stations and building

cooling.

Figure : Cooling Tower System

Cooling Tower Specification

Brand: Polacel Model: sq 2500T


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Type: induce draft cross flow Capacity(Refrigeration tons, Rt): 2500 Water flow: 5000 IGPM(Imperial Gallon per Minutes)

Water temp(F): in(97) & out(87) Fan power: [7.5 kW x 8]There are 8 cooling towers for the system. 4 cooling towers are placed at the

rooftop of Block 3(cooling tower 1) and the other 4 are located at rooftop of

Block 4(cooling tower 2). The cooling tower 1 is used for chiller 1 and

cooling tower 2 for chiller 2. The usage will also alternate periodically.

3. Ice Cells

There are 45 ice cells that located underneath the parking area of Block 5 of

S&T and 28 ice cells located opposite the Block 5.

Figure: Ice Cell

Thermal energy storage may refer to energy is store in a thermal

reservoir for later reuse. They can be employed to balance energy demand


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between day time and night time. The thermal reservoir may be maintained at

a temperature above (hotter) or below (colder) than that of the ambient

environment. The principal application today is the production of ice, chilled

water, or eutectic solution at night, which is then used to cool environments

during the day.

The specification:

Unit label: ice cell 1 -45 Description: TES tank Make: Dunham-Bush Model: Ts 240. Type: tube in tank Capacity rated: 240 Refrigerant tons hour(Rth) ; Norminal 10800 Rth Function to storage energy in ice produced by chiller at night.

4. Primary and Secondary Pump

Figure : Primary Pump


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Figure : Schematic of Primary & Secondary Pump

The Specification:

Brand : Regent Model : R10 / 12 CME Type : Horizontal Split Casing Pump Capacity : 4500 IGPM Head : 150 ft Load : 275 Hp


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5. Condenser Water Pump

Figure : Condenser Water Pump

Figure : Schematic of Condenser Water Pump


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The Specification:

Brand : Regent Model : R200/300 BST Type: Horizontal Split Casing Capacity: 2600 IGPM Head : 90 ft Load : 100 Hp

6. Heat Exchanger

Figure : Heat Exchanger


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Figure : Schematic for Heat Exchanger

The heat exchangers are used to transfer heat between two fluids. In the

TES district cooling system, glycol and water are used in the flow of

pipeline. The glycol function is not to produce ice. The glycol property that is

will remain in liquid form even the temperature is below zero degree. So,

during the ice making, the glycol will not freeze and still can transfer the cool

temperature throughout the system. The ice temperature is transferred to the

glycol so that the glycol could transfer the cool temperature to the building.

The usage of heat exchangers, ice cells and the low temperature during ice

making at night reduce the burden of chillers in operation.

Specification of Heat Exchangers

Amount of Heat Exchangers: 4 Manufacturer: Alfa Laval Model: MX25-BFG Type: Counter flow Flow rate (usgpm): Hot 2400 & cold 2400 In/out temp (C): hot 13.3/6.6 & cold 4.4/6.6 Heat exchanger (Rt): 1283.33 Function to exchange heat from glycol-water pipe line to water onlypipe line

*Usgpm: US gallon per minute


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7. Air Handling Unit (AHU)An air handler, or air handling unit (often abbreviated to AHU), is a

device used to condition and circulate air as part of a heating, ventilating,

and air-conditioning (HVAC) system. Usually, an air handler is a large

metal box containing a blower, heating and/or cooling elements filter

racks or chambers, sound attenuators, and dampers. Air handlers usually

connect to ductwork that distributes the conditioned air through the

building, and returns it to the AHU. Sometimes AHUs discharge (supply)

and admit (return) air directly to and from the space served, without

ductwork.

Figure : AHU Ducting

AHU Components:

BlowerAir handlers typically employ a large squirrel cage blower driven

by an AC induction electric motor to move the air. The blower

may operate at a single speed, offer a variety of pre-set speeds, or

be driven by a Variable Frequency Drive so as to allow a wide

range of air flow rates. Flow rate may also be controlled by inlet

vanes or outlet dampers on the fan.

Cooling / Heating CoilLarge commercial air handling units contain coils that circulate

hot water or steam for heating, and chilled water for cooling. The

hot water or steam is provided by a central boiler, and the chilled

water is provided by a central chiller


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FilterAir filtration is almost always present in order to provide clean

dust-free air to the building occupants. It may be via simple low-

MERV pleated media, HEPA, electrostatic, or a combination of

techniques. Gas-phase and ultraviolet air treatments may be

employed as well. It is typically placed first in the AHU in order

to keep all its components clean.

Control SystemControls are necessary to regulate every aspect of an air handler,

such as: flow rate of air, supply air temperature, mixed air

temperature, humidity, air quality. They may be as simple as an

off/on thermostat or as complex as a building automation system.

Common control components include temperature sensors,

humidity sensors, sail switches, actuators, motors, and controllers.

Figure : Building Air Distribution


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8. Building Automation System (BAS)

S&T Complex applied Building Automation System (BAS). This system

to ease the maintenance and operation services by controlling the whole

system in the building included TES, elevators, and Fire Fighting System

in one Control Room. The Fan Coil Unit and Air Handling Unit can be

controlled in the room without going to each level to adjust the flowrate

or just to on or off the units respectively. Overall system also can be

monitored through BAS. It also can schedule the AHU and FCU

operation.

Figure : S&T Layout in BAS


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Figure : Schedule for AHU

4.1.3. Design Consideration and OperationThermal energy storage can refer to a number of technologies that

store energy in a thermal/ice reservoir for later reuse. They can be employed to

balance energy demand between day time and night time. The thermal

reservoir may be maintained at a temperature above (hotter) or below (colder)

than that of the ambient environment.

In this application a relatively standard chiller is run at night to

produce a pile of ice. Water is circulated through the pile/cell during the day to

produce chilled water that would normally be the daytime output of the

chillers.


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Operation:

Diagram 1: Operational flow of TES in S&T

Chiller Plant Control Module

i. Automated chiller control and monitoring system.ii.

Powered by Opto22 hardware and software technology connected tothe Dunham Bush NC25-4 Microprocessor to directly access control

and data points.

iii. Precise and details access to the current system informationiv. Accessibility of system data results in faster responsev. Computer aided scheduling that improves the utilization of machines

and increases efficiency.

vi. Real-time system data

Plant OperationCharging Mode

i. 2 primary Ethylene Glycol Pump (PEGP 275hp each) each controlledby VSD.

ii. Condenser water pumps (CWP) 1, 2, 3 and 4 with cooling tower (CT) 1and 2.

iii. Motorized valve V3 open with motorized valve V8, V9, V10, V12,heat exchanger closed.

The tank is filled withwater submerged a

polyethylene tube heat

exchanger

A glycol solution (-3.3C)flowing inside the tubescauses the surrounding

water to freeze

The chilled Glycol solutionis typically provided by achiller having 24 tons (84

kW) cooling capacity

When fully frozen, the ice

cell stores 240 ton-hour(844 kWh) cooling capacity

Requires 10 hoursoperation of a 24 ton

chiller to fully freeze thewater in the tank

To serve, the ice melted ata rate dictated by load

The Glycol solution flowsfrom the ice cell to the

load device


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iv. 3 chillers (900 RT each) start by sequence instruction from the chillersplant control module.

v. Modulating valve V2 open 100% and V1 closed.vi. Flow rate in the range of 6000 GPM until 8000 GPM.

Plant OperationDischarging Mode

i. 1 Primary Ethylene Glycol Pump (PEGP 275hp each) each controlledby VSD.

ii. Condenser water pump 1 and 2 with cooling tower (either CT 1 or 2)iii. Motorized valve V3 closed with valve V8, V9, V10 for heat exchanger

open.

iv. 2 Chillers (900 RT each) will be start by the sequence instruction fromthe chiller plant control module.

v. Secondary chilled water pump (SCHWP) 3 and 4 start.vi. Modulating valve V1 and V2 will modulate depends on the

temperature set point 44 F.

vii. Flow rate in the range of 5000 GPM until 7000 GPM

Thermal Energy Storage with Ice Storage was preferable to be installed in the

complex due to spatial and the advantages gained.

Thermal storage systems offer building owners the potential for substantial

cost savings by using off-peak electricity to produce chilled water or ice.

A thermal energy storage system benefits consumers primarily in three ways:

1. Load Shifting

2. Lower Capital Outlays

3. Efficiency in Operation

1) Load shifting

Load shifting is primarily the main reason to install a TES system. Since TES works during off-peak energy, advantage of electrical

utilities lower time-of-use rate could be taken.

TES benefits in lower operating costs by saving money on electricbills and avoiding on-peak demand charges.


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TES benefits on reduced demand for electricity during the peakdemand periods. Many utilities offer cash incentives and rebates

for installing or converting to TES. TNB offers off-peak rate

which are less expensive and reduce the cost.

o Low energy cost - approximately 20% lower.o Low TNB maximum demand (MD) charges

approximately 30% lower.

o Lower production cost per unit of cooling energy.o No huge capital outlay for air-conditioning plant by

building owner.

o For TNBhelps to improve (flatten) its daily load curverational for off-peak tariff.

2. Lower Capital Outlays:

Capital costs incurred are comparable to conventional air-conditioningsystem, with cost saved by using a small refrigeration plant. Storage

systems let chillers operate at full load all night instead of operating at

full or part load during the day. Depending on the system

configuration, the chiller may be smaller than would be required for

direct cooling, allowing smaller auxiliaries such as cooling-tower fans,

condenser water pumps, or condenser fans. TES tanks allow a

reduction of chiller capacity requirements. This is true for both new

construction and system expansions. Lower equipment requirements

translate to reduce maintenance needs.

A TES system takes up less space and, when designed in conjunctionwith an air distribution system and installed during a building's

construction phase, requires smaller ducts and fan motors. This can

reduce spacing between floors and save money.

3. Efficiency in Operation:

Conventional systems only operate at partial operating conditions mostof the time. In contrast, the chiller used in a TES system operates at


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full-load conditions for a shorter period of time while the system is

being charged. The equipment's operating efficiency increases. TES

system chillers always either run in its full efficiency or not at all. In

other words the chiller operation is not dependent on the varying load

profile of the building.

Additionally, because the stored cooling equipment typically operatesat night when outdoor air temperatures are cooler, heat rejection is

improved. The condenser always sees low ambient dry and wet bulb

temperatures. The net effect is usually a net decrease in kWh

consumption; by anywhere from a few percent to a few tens of percent.

TES system provides operational flexibility because the reservedstorage capacity ensures enough buffers for varying loads of minimum

and maximum demand. Chillers can be stopped during normal working

hours for maintenance and service while the ice stored during off-peak

period supplies cooling.

TES design flexibility

FULL STORAGE PARTIAL STORAGE PARTIAL STORAGE(LIMIT DEMAND)

To meet all on-peak cooling

loads from storages.

To meet part of the cooling

load from storage and part

directly from chiller, and

discharged when the load is

greater than the chiller

output.

Limit demand, control to

minimize site peak demand,

low cost.

4.1.4. References1. Air Conditioning with Thermal Energy Storage. (n.d.). Retrieved July 25,2011, from PDHengineer.com: www.pdhengineer.com/pages/HV-4005.htm

2. Aziz, M. (2010). Review on Performance of Thermal Energy Storage Systemat S & T Complex, UiTM Shah Alam, Selangor. 2010 IEEE Control and System

Graduate Research Colloquium , 49-54.


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Science and Technolgy Complex