Buildings.Fluid.HeatExchangers.DXCoils

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Buildings.Fluid.HeatExchangers.DXCoils

DX(Direct Expansion) cooling coil models

Information

This package contains DX coil models.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name	Description
UsersGuide	User's Guide
MultiStage	Multi-stage DX cooling coil
SingleSpeed	Single speed DX cooling coil
VariableSpeed	Variable speed DX cooling coil
Data	Package with performance data for DX cooling coil
Examples	Package with example of DX cooling coil models
Validation	Collection of validation models
BaseClasses	Package with base classes for DX cooling coil model

Buildings.Fluid.HeatExchangers.DXCoils.MultiStage

Multi-stage DX cooling coil

Buildings.Fluid.HeatExchangers.DXCoils.MultiStage

Information

This model can be used to simulate a DX cooling coil with multiple operating stages. Depending on the used performance curves, each stage could be a different compressor speed, or a different mode of operation, such as with or without hot gas reheat.

See Buildings.Fluid.HeatExchangers.DXCoils.UsersGuide for an explanation of the model.

Extends from Buildings.Fluid.HeatExchangers.DXCoils.BaseClasses.PartialDXCoil (Partial model for DX coil).

Parameters

Type	Name	Default	Description
DXCoil	datCoi		Performance data
replaceable package Medium		PartialCondensingGases	Medium model
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
PressureDifference	dp.start	0	Pressure difference between port_a and port_b [Pa]
Nominal condition
PressureDifference	dp_nominal		Pressure difference [Pa]
Assumptions
Boolean	allowFlowReversal	true	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	homotopyInitialization	true	= true, use homotopy method
Diagnostics
Boolean	show_T	false	= true, if actual temperature at port is computed
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Nominal condition
Time	tau	30	Time constant at nominal flow (if energyDynamics <> SteadyState) [s]
Equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Dynamics	massDynamics	energyDynamics	Type of mass balance: dynamic (3 initialization options) or steady state
Moisture balance
Boolean	computeReevaporation	true	Set to true to compute reevaporation of water that accumulated on coil
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	T_start	Medium.T_default	Start value of temperature [K]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
input RealInput	TConIn	Outside air dry bulb temperature for an air cooled condenser or wetbulb temperature for an evaporative cooled condenser [K]
output RealOutput	P	Electrical power consumed by the unit [W]
output RealOutput	QSen_flow	Sensible heat flow rate [W]
output RealOutput	QLat_flow	Latent heat flow rate [W]
input IntegerInput	stage	Stage of cooling coil (0: off, 1: first stage, 2: second stage...)

Modelica definition

model MultiStage "Multi-stage DX cooling coil" extends Buildings.Fluid.HeatExchangers.DXCoils.BaseClasses.PartialDXCoil( dxCoo(final variableSpeedCoil=false)); Modelica.Blocks.Interfaces.IntegerInput stage "Stage of cooling coil (0: off, 1: first stage, 2: second stage...)"; BaseClasses.SpeedSelect speSel(nSta=datCoi.nSta, speSet=datCoi.sta.spe); Modelica.Blocks.Math.IntegerToBoolean onSwi(final threshold=1) "On/off switch"; equation connect(onSwi.y, eva.on); connect(onSwi.u, stage); connect(stage, speSel.stage); connect(speSel.speRat, dxCoo.speRat); connect(stage, dxCoo.stage); end MultiStage;

Buildings.Fluid.HeatExchangers.DXCoils.SingleSpeed

Single speed DX cooling coil

Buildings.Fluid.HeatExchangers.DXCoils.SingleSpeed

Information

This model can be used to simulate a DX cooling coil with single speed compressor.

See Buildings.Fluid.HeatExchangers.DXCoils.UsersGuide for an explanation of the model.

Extends from Buildings.Fluid.HeatExchangers.DXCoils.BaseClasses.PartialDXCoil (Partial model for DX coil).

Parameters

Type	Name	Default	Description
DXCoil	datCoi		Performance data
replaceable package Medium		PartialCondensingGases	Medium model
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
PressureDifference	dp.start	0	Pressure difference between port_a and port_b [Pa]
Nominal condition
PressureDifference	dp_nominal		Pressure difference [Pa]
Assumptions
Boolean	allowFlowReversal	true	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	homotopyInitialization	true	= true, use homotopy method
Diagnostics
Boolean	show_T	false	= true, if actual temperature at port is computed
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Nominal condition
Time	tau	30	Time constant at nominal flow (if energyDynamics <> SteadyState) [s]
Equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Dynamics	massDynamics	energyDynamics	Type of mass balance: dynamic (3 initialization options) or steady state
Moisture balance
Boolean	computeReevaporation	true	Set to true to compute reevaporation of water that accumulated on coil
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	T_start	Medium.T_default	Start value of temperature [K]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
input RealInput	TConIn	Outside air dry bulb temperature for an air cooled condenser or wetbulb temperature for an evaporative cooled condenser [K]
output RealOutput	P	Electrical power consumed by the unit [W]
output RealOutput	QSen_flow	Sensible heat flow rate [W]
output RealOutput	QLat_flow	Latent heat flow rate [W]
input BooleanInput	on	Set to true to enable compressor, or false to disable compressor

Modelica definition

model SingleSpeed "Single speed DX cooling coil" extends Buildings.Fluid.HeatExchangers.DXCoils.BaseClasses.PartialDXCoil( dxCoo(final variableSpeedCoil=false), final nSta=1); Modelica.Blocks.Sources.Constant speRat(final k=1) "Speed ratio"; Modelica.Blocks.Interfaces.BooleanInput on "Set to true to enable compressor, or false to disable compressor"; protected Modelica.Blocks.Math.BooleanToInteger onSwi( final integerTrue=1, final integerFalse=0) "On/off switch"; equation connect(speRat.y, dxCoo.speRat); connect(eva.on, on); connect(on, onSwi.u); connect(onSwi.y, dxCoo.stage); end SingleSpeed;

Buildings.Fluid.HeatExchangers.DXCoils.VariableSpeed

Variable speed DX cooling coil

Buildings.Fluid.HeatExchangers.DXCoils.VariableSpeed

Information

This model can be used to simulate a DX cooling coil with continuously variable speed compressors. The control input is the speed ratio. The coil will switch off if the speed ratio is below a minimum value.

See Buildings.Fluid.HeatExchangers.DXCoils.UsersGuide for an explanation of the model.

Extends from Buildings.Fluid.HeatExchangers.DXCoils.BaseClasses.PartialDXCoil (Partial model for DX coil).

Parameters

Type	Name	Default	Description
DXCoil	datCoi		Performance data
replaceable package Medium		PartialCondensingGases	Medium model
Real	minSpeRat		Minimum speed ratio
Real	speRatDeaBan	0.05	Deadband for minimum speed ratio
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
PressureDifference	dp.start	0	Pressure difference between port_a and port_b [Pa]
Nominal condition
PressureDifference	dp_nominal		Pressure difference [Pa]
Assumptions
Boolean	allowFlowReversal	true	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	homotopyInitialization	true	= true, use homotopy method
Diagnostics
Boolean	show_T	false	= true, if actual temperature at port is computed
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Nominal condition
Time	tau	30	Time constant at nominal flow (if energyDynamics <> SteadyState) [s]
Equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Dynamics	massDynamics	energyDynamics	Type of mass balance: dynamic (3 initialization options) or steady state
Moisture balance
Boolean	computeReevaporation	true	Set to true to compute reevaporation of water that accumulated on coil
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	T_start	Medium.T_default	Start value of temperature [K]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
input RealInput	TConIn	Outside air dry bulb temperature for an air cooled condenser or wetbulb temperature for an evaporative cooled condenser [K]
output RealOutput	P	Electrical power consumed by the unit [W]
output RealOutput	QSen_flow	Sensible heat flow rate [W]
output RealOutput	QLat_flow	Latent heat flow rate [W]
input RealInput	speRat	Speed ratio

Modelica definition

model VariableSpeed "Variable speed DX cooling coil" extends Buildings.Fluid.HeatExchangers.DXCoils.BaseClasses.PartialDXCoil( dxCoo(final variableSpeedCoil=true)); parameter Real minSpeRat(min=0,max=1) "Minimum speed ratio"; parameter Real speRatDeaBan= 0.05 "Deadband for minimum speed ratio"; Modelica.Blocks.Interfaces.RealInput speRat "Speed ratio"; protected Modelica.Blocks.Logical.Hysteresis deaBan( uLow=minSpeRat - speRatDeaBan/2, uHigh=minSpeRat + speRatDeaBan/2) "Speed ratio deadband"; Modelica.Blocks.Math.BooleanToInteger onSwi( final integerTrue=1, final integerFalse=0) "On/off switch"; equation connect(speRat, dxCoo.speRat); connect(speRat, deaBan.u); connect(deaBan.y, eva.on); connect(onSwi.y, dxCoo.stage); connect(deaBan.y, onSwi.u); end VariableSpeed;

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