Equation solvers

• Matlab

• Free versions / open source codes:

–Scilab http://www.scilab.org/

• MathCad:• Mathematica: http://www.wolfram.com/mathematica/

• LabView: http://www.ni.com/labview/

• EES: http://www.fchart.com/ees/

• Modelica: https://www.modelica.org/

• ….

Open Studio Lab Class

• This Thursday 4 pm

• Computer lab ECJ 3.402

• Instructor: Wesley Cole

Lecture Objectives:

• Building-System-Plant connection

Building-System-Plant

Plant(boilerand/orChiller)

Building

HVAC System(AHU and distribution systems)

Building HVAC Systems (Primary and Secondary Building Systems)

AHU

Buildingenvelope

Cooling(chiller)

(or Gas)

Electricity

Gas

Heating(boilers)

Fresh air For ventilation

Distribution systems

Air transport

Secondary systems

Primarysystems

AHU – Air Handling Unit

HVAC systems affect the energy efficiency of the building as much as the building envelope

Air-conditioning in Air Handling Unit (AHU)

Compressorand Condenser

Roof top AHU

Gas/Electric Heater

to building

Fan

air from building

fresh air

Evaporator

filtermixing

hotwatercool

water

Return fan

Supply fan

flow control dampers

AHU

Fresh air

AHU schematic

Outdoor air To room

Exhaust From room

Processes in AHU presented in Psychrometric in psychrometric

OA Case forSummer in Austin

IA

MA

SA

Refrigeration Cycle

T outdoor air

T cooled water

Cooling energy (evaporator)

Released energy (condenser)

- What is COP?- How the outdoor air temperature affects chiller performance?

Integration of HVAC and building physics models

BuildingHeating/Cooling

SystemPlant

BuildingHeating/Cooling

SystemPlant

Load System Plant model

Integrated models

Qbuiolding Q

including

Ventilation

and

Dehumidification

Example of System Models:Schematic of simple air handling unit (AHU)

rmSfans

cooler heater

mS

QC QH

wO wS

TR

room TR

Qroom_sensibel

(1-r)mS mS

wM

wR

Qroom_latent

TSTO

wR

TM

Tf,inTf,out

m - mass flow rate [kg/s], T – temperature [C], w [kgmoist/kgdry air], r - recirculation rate [-], Q energy/time [W]

Mixing box

Energy and mass balance equations for Air handling unit model – steady state case

SRpSsensibleroom TTcmQ _

mS is the supply air mass flow rate

cp - specific capacity for air,

TR is the room temperature,

TS is the supply air temperature.

changephaseSRSlatentroom iwwmQ __ wR and wS are room and supply humidity ratio

changephasei _ - energy for phase change of water into vapor

The energy balance for the room is given as:

The air-humidity balance for room is given as:

The energy balance for the mixing box is:

ROM TrTrT )1(‘r’ is the re-circulated air portion, TO is the outdoor air temperature, TM is the temperature of the air after the mixing box.

The air-humidity balance for the mixing box is:

ROM wrwrw )1(wO is the outdoor air humidity ratio and

wM is the humidity ratio after the mixing box

)( MSpSHeating TTcmQ

The energy balance for the heating coil is given as:

The energy balance for the cooling coil is given as:

changephaseMSSMSpSCooling iwwmTTcmQ _)(

Non-air system Radiant panel heat transfer model

Room (zone 1)

Radiant Panelc onv ecti

onTsurface

Tsurounding

Tzone_air rad iat ion

Qrad_pan

radiant panel layer (water tube)

air supplysystem

m ,T = const.s s

Qzone

Tw_out Tw_in

Non-air system Radiant panel heat transfer model

)()( __sup_sup airroomairplyairplypair TTmcQ

panradQ _

airpanradzone QQQ _

)()( ,,_ airpanelpanelconvisurfacepanelpaneliradiationconvradiationpanrad TTAhTTAhQQQ

)( ___ inwoutwpwpanrad TTmcQ

The total cooling/heating load in the room

The energy extracted/added by air system

The energy extracted/added by the radiant panel:

The radiant panel energy is:

The energy extracted/added by the radiant panel is the sum of the radiative and convective parts: