modelSpaceCooling

Space cooling with DX coils

Extends from Modelica.Icons.Example (Icon for runnable examples).

Information

This model illustrates the use of the air source DX coil models with single speed compressor, multi-stage compressor, and variable speed compressor. The three systems all have the same simple model for a room, and the same HVAC components, except for the coil. The top system has a DX coil with single speed compressor and on/off control with dead-band. The middle system has a DX coil with two stages, each representing a different compressor speed. The bottom system has a DX coil with variable speed control for the compressor.

All coils are controlled based on the respective room air temperature. The plot below shows how room air temperatures and humidity levels are controlled with the respective coils. The single speed coil has the highest room air humidity level because during its off-time, water that accumulated on the coil evaporates into the air stream. This effect is smaller for the coil with two compressor stages and for the coil with variable compressor speed, as both of these coils switch off less frequent.

Implementation

The model is based on Buildings.Examples.Tutorial.SpaceCooling.System3.

Parameters

Type	Name	Default	Description
Modelica.Units.SI.Volume	V	6103	Room volume
Real	eps	0.8	Heat recovery effectiveness
Modelica.Units.SI.Temperature	TASup_nominal	273.15 + 18	Nominal air temperature supplied to room
Modelica.Units.SI.Temperature	TRooSet	273.15 + 24	Nominal room air temperature
Modelica.Units.SI.Temperature	TOut_nominal	273.15 + 30	Design outlet air temperature
Modelica.Units.SI.Temperature	THeaRecLvg	TOut_nominal - eps*(TOut_nominal - TRooSet)	Air temperature leaving the heat recovery
Modelica.Units.SI.HeatFlowRate	QRooInt_flow	1000	Internal heat gains of the room
Modelica.Units.SI.HeatFlowRate	QRooC_flow_nominal	-QRooInt_flow - 10E3/30*(TOut_nominal - TRooSet)	Nominal cooling load of the room
Modelica.Units.SI.MassFlowRate	mA_flow_nominal	1.3*QRooC_flow_nominal/1006/(TASup_nominal - TRooSet)	Nominal air mass flow rate, increased by factor 1.3 to allow for recovery after temperature setback
Modelica.Units.SI.TemperatureDifference	dTFan	2	Estimated temperature raise across fan that needs to be made up by the cooling coil
Modelica.Units.SI.HeatFlowRate	QCoiC_flow_nominal	(QRooC_flow_nominal + mA_flow_nominal(TASup_nominal - THeaRecLvg - dTFan)1006)	Cooling load of coil, taking into account economizer, and increased due to latent heat removal
Buildings.Fluid.DXSystems.Cooling.AirSource.Data.Generic.DXCoil	datCoi		Data record for single-speed coil
Buildings.Fluid.DXSystems.Cooling.AirSource.Data.Generic.DXCoil	datCoiMulSpe		Coil data multi-stage and variable speed cooling coils

Connectors

Type	Name	Default	Description
BoundaryConditions.WeatherData.Bus	weaBus		Weather bus

Components

Type	Name	Description
Buildings.Fluid.Movers.FlowControlled_m_flow	fan	Supply air fan
Buildings.Fluid.HeatExchangers.ConstantEffectiveness	hex	Heat recovery
Buildings.Fluid.Sources.Outside	out	Source for outdoor air
BoundaryConditions.WeatherData.ReaderTMY3	weaDat	Weather data reader
Modelica.Blocks.Sources.Constant	mAir_flow	Fan air flow rate
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemHXEvaOut	Temperature sensor for heat recovery outlet on supply side
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemSupAir	Temperature sensor for supply air
Modelica.Blocks.Logical.OnOffController	con	Controller to enable component when measurement falls below setpoint
Modelica.Blocks.Sources.Constant	TRooSetPoi	Room temperature set point
Buildings.Fluid.DXSystems.Cooling.AirSource.SingleSpeed	sinSpeDX	Single-speed DX cooling coil
SimpleRoom	rooSinSpe	Room model connected to single speed coil
Buildings.Fluid.Movers.FlowControlled_m_flow	fan1	Supply air fan
Buildings.Fluid.HeatExchangers.ConstantEffectiveness	hex1	Heat recovery
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemHXEvaOut1	Temperature sensor for heat recovery outlet on supply side
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemSupAir1	Temperature sensor for supply air
Buildings.Fluid.DXSystems.Cooling.AirSource.MultiStage	mulStaDX	Multi-speed DX coil
SimpleRoom	rooMulSpe	Room model connected to multi stage coil
ControllerTwoStage	mulSpeCon	Controller for multi-stage coil
SimpleRoom	rooVarSpe	Room model connected to variable speed coil
Buildings.Fluid.Movers.FlowControlled_m_flow	fan2	Supply air fan
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemSupAir2	Temperature sensor for supply air
Buildings.Fluid.DXSystems.Cooling.AirSource.VariableSpeed	varSpeDX	Variable-speed DX coil
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemHXEvaOut2	Temperature sensor for heat recovery outlet on supply side
Buildings.Fluid.HeatExchangers.ConstantEffectiveness	hex2	Heat recovery
Modelica.Blocks.Continuous.Integrator	sinSpePow	Power consumed by single speed coil
Modelica.Blocks.Continuous.Integrator	mulSpePow	Power consumed by multi-stage coil
Modelica.Blocks.Continuous.Integrator	varSpePow	Power consumed by multi-stage coil
Modelica.Blocks.Logical.Not	not1	Turn on DX coil when measured temperature is above setpoint
Buildings.Controls.Continuous.LimPID	conVarSpe	Controller for variable speed DX coil

Name	Description
Medium	Fluid medium for the model
SimpleRoom	Simple model of a room
ControllerTwoStage	Controller for two stage coil

Revisions

March 19, 2023 by Xing Lu and Karthik Devaprasad:
Updated instance classes for sinSpeDX, mulStaDX, varSpeDX, and datCoiMulSpe.
Updated connection statements to reflect change in input instance from TConIn to TOut in sinSpeDX, mulStaDX and varSpeDX.
Updated comments and formatting for ease of understanding and readability.
September 24, 2015 by Michael Wetter:
Set start attributes in SimpleRoom so that the model translates when using the pedantic mode in Dymola 2016. This is for #426.
December 22, 2014 by Michael Wetter:
Removed Modelica.Fluid.System to address issue #311.
September 13, 2013, by Michael Wetter:
Changed control implementation of variable speed coil to use a proportional controller.
January 11, 2012, by Michael Wetter:
First implementation.