Buildings.Fluid.HeatPumps

Package with models for heat pumps

Information

This package contains component models for heat pumps.

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

Package Content

Name Description
Buildings.Fluid.HeatPumps.Carnot_TCon Carnot_TCon Heat pump with prescribed condenser leaving temperature and performance curve adjusted based on Carnot efficiency
Buildings.Fluid.HeatPumps.Carnot_y Carnot_y Reversible heat pump with performance curve adjusted based on Carnot efficiency
Buildings.Fluid.HeatPumps.ReciprocatingWaterToWater ReciprocatingWaterToWater Model for a reciprocating water to water heat pump
Buildings.Fluid.HeatPumps.ScrollWaterToWater ScrollWaterToWater Model for a scroll water to water heat pump
Buildings.Fluid.HeatPumps.Calibration Calibration Package for calibration of heat pump models
Buildings.Fluid.HeatPumps.Compressors Compressors Package with compressor models
Buildings.Fluid.HeatPumps.Data Data Package with model parameters for heat pumps
Buildings.Fluid.HeatPumps.Examples Examples Collection of models that illustrate model use and test models
Buildings.Fluid.HeatPumps.Validation Validation Collection of models that validate the heat pump models
Buildings.Fluid.HeatPumps.BaseClasses BaseClasses Package with base classes for Buildings.Fluid.HeatPumps

Buildings.Fluid.HeatPumps.Carnot_TCon Buildings.Fluid.HeatPumps.Carnot_TCon

Heat pump with prescribed condenser leaving temperature and performance curve adjusted based on Carnot efficiency

Buildings.Fluid.HeatPumps.Carnot_TCon

Information

This is a model of a heat pump whose coefficient of performance COP changes with temperatures in the same way as the Carnot efficiency changes. The control input is the setpoint of the condenser leaving temperature, which is met exactly at steady state if the heat pump has sufficient capacity.

The model allows to either specify the Carnot effectivness ηCarnot,0, or a COP0 at the nominal conditions, together with the evaporator temperature Teva,0 and the condenser temperature Tcon,0, in which case the model computes the Carnot effectivness as

ηCarnot,0 = COP0 ⁄ (Tcon,0 ⁄ (Tcon,0-Teva,0)).

The heat pump COP is computed as the product

COP = ηCarnot,0 COPCarnot ηPL,

where COPCarnot is the Carnot efficiency and ηPL is a polynomial in heating part load ratio yPL that can be used to take into account a change in COP at part load conditions. This polynomial has the form

ηPL = a1 + a2 yPL + a3 yPL2 + ...

where the coefficients ai are declared by the parameter a.

On the Dynamics tag, the model can be parametrized to compute a transient or steady-state response. The transient response of the model is computed using a first order differential equation for the evaporator and condenser fluid volumes. The heat pump outlet temperatures are equal to the temperatures of these lumped volumes.

Typical use and important parameters

When using this component, make sure that the condenser has sufficient mass flow rate. Based on the evaporator mass flow rate, temperature difference and the efficiencies, the model computes how much heat will be removed by to the evaporator. If the mass flow rate is too small, very low outlet temperatures can result, possibly below freezing.

The condenser heat flow rate QCon_flow_nominal is used to assign the default value for the mass flow rates, which are used for the pressure drop calculations. It is also used to compute the part load efficiency. Hence, make sure that QCon_flow_nominal is set to a reasonable value.

The maximum heating capacity is set by the parameter QCon_flow_max, which is by default set to infinity.

The coefficient of performance depends on the evaporator and condenser leaving temperature since otherwise the second law of thermodynamics may be violated.

Notes

For a similar model that can be used as a chiller, see Buildings.Fluid.Chillers.Examples.Carnot_TEva.

Extends from Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_T (Partial model for chiller with performance curve adjusted based on Carnot efficiency).

Parameters

TypeNameDefaultDescription
replaceable package Medium1PartialMediumMedium 1 in the component
replaceable package Medium2PartialMediumMedium 2 in the component
HeatFlowRateQCon_flow_maxModelica.Constants.infMaximum heat flow rate for heating (positive) [W]
Nominal condition
MassFlowRatem1_flow_nominalQCon_flow_nominal/cp1_defaul...Nominal mass flow rate [kg/s]
MassFlowRatem2_flow_nominalQEva_flow_nominal/cp2_defaul...Nominal mass flow rate [kg/s]
HeatFlowRateQEva_flow_nominal-QCon_flow_nominal*(COP_nomi...Nominal cooling heat flow rate (QEva_flow_nominal < 0) [W]
HeatFlowRateQCon_flow_nominal Nominal heating flow rate [W]
TemperatureDifferencedTEva_nominal-10Temperature difference evaporator outlet-inlet [K]
TemperatureDifferencedTCon_nominal10Temperature difference condenser outlet-inlet [K]
Pressuredp1_nominal Pressure difference over condenser [Pa]
Pressuredp2_nominal Pressure difference over evaporator [Pa]
Efficiency
Booleanuse_eta_Carnot_nominaltrueSet to true to use Carnot effectiveness etaCarnot_nominal rather than COP_nominal
RealetaCarnot_nominalCOP_nominal/(TUseAct_nominal...Carnot effectiveness (=COP/COP_Carnot) used if use_eta_Carnot_nominal = true [1]
RealCOP_nominaletaCarnot_nominal*TUseAct_no...Coefficient of performance at TEva_nominal and TCon_nominal, used if use_eta_Carnot_nominal = false [1]
TemperatureTCon_nominal303.15Condenser temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K]
TemperatureTEva_nominal278.15Evaporator temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K]
Reala[:]{1}Coefficients for efficiency curve (need p(a=a, yPL=1)=1)
TemperatureDifferenceTAppCon_nominalif cp1_default < 1500 then 5...Temperature difference between refrigerant and working fluid outlet in condenser [K]
TemperatureDifferenceTAppEva_nominalif cp2_default < 1500 then 5...Temperature difference between refrigerant and working fluid outlet in evaporator [K]
Assumptions
BooleanallowFlowReversal1true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1
BooleanallowFlowReversal2true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2
Advanced
MassFlowRatem1_flow_small1E-4*abs(m1_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRatem2_flow_small1E-4*abs(m2_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed
Flow resistance
Condenser
Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar [1]
Evaporator
Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar [1]
Dynamics
Condenser
Timetau160Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT1_startMedium1.T_defaultInitial or guess value of set point [K]
Evaporator
Timetau260Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT2_startMedium2.T_defaultInitial or guess value of set point [K]
Evaporator and condenser
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state

Connectors

TypeNameDescription
FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
output RealOutputQCon_flowActual heating heat flow rate added to fluid 1 [W]
output RealOutputPElectric power consumed by compressor [W]
output RealOutputQEva_flowActual cooling heat flow rate removed from fluid 2 [W]
input RealInputTSetCondenser leaving water temperature [K]

Modelica definition

model Carnot_TCon "Heat pump with prescribed condenser leaving temperature and performance curve adjusted based on Carnot efficiency" extends Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_T( final COP_is_for_cooling = false, final QEva_flow_nominal = -QCon_flow_nominal*(COP_nominal-1)/COP_nominal, PEle(y=QCon_flow/COP), redeclare HeatExchangers.Heater_T con( final from_dp=from_dp1, final dp_nominal=dp1_nominal, final linearizeFlowResistance=linearizeFlowResistance1, final deltaM=deltaM1, final QMax_flow=QCon_flow_max, final tau=tau1, final T_start=T1_start, final energyDynamics=energyDynamics, final homotopyInitialization=homotopyInitialization), redeclare HeatExchangers.HeaterCooler_u eva( final from_dp=from_dp2, final dp_nominal=dp2_nominal, final linearizeFlowResistance=linearizeFlowResistance2, final deltaM=deltaM2, final tau=tau2, final T_start=T2_start, final energyDynamics=energyDynamics, final homotopyInitialization=homotopyInitialization, final Q_flow_nominal=QEva_flow_nominal)); parameter Modelica.SIunits.HeatFlowRate QCon_flow_max( min=0) = Modelica.Constants.inf "Maximum heat flow rate for heating (positive)"; Modelica.Blocks.Interfaces.RealInput TSet(unit="K") "Condenser leaving water temperature"; protected Modelica.Blocks.Math.Gain yEva(final k=1/QEva_flow_nominal) "Normalized evaporator heat flow rate"; Modelica.Blocks.Math.Add QEva_flow_internal(final k1=-1) "Heat removed by evaporator"; initial equation assert(QCon_flow_nominal > 0, "Parameter QCon_flow_nominal must be positive."); assert(COP_nominal > 1, "The nominal COP of a heat pump must be bigger than one."); equation connect(TSet, con.TSet); connect(con.Q_flow, QCon_flow); connect(QEva_flow_internal.u1, con.Q_flow); connect(QEva_flow_internal.u2, PEle.y); connect(QEva_flow_internal.y, yEva.u); connect(QEva_flow, QEva_flow_internal.y); connect(yEva.y, eva.u); end Carnot_TCon;

Buildings.Fluid.HeatPumps.Carnot_y Buildings.Fluid.HeatPumps.Carnot_y

Reversible heat pump with performance curve adjusted based on Carnot efficiency

Buildings.Fluid.HeatPumps.Carnot_y

Information

This is model of a heat pump whose coefficient of performance COP changes with temperatures in the same way as the Carnot efficiency changes. The input signal y is the control signal for the compressor.

The model allows to either specify the Carnot effectivness ηCarnot,0, or a COP0 at the nominal conditions, together with the evaporator temperature Teva,0 and the condenser temperature Tcon,0, in which case the model computes the Carnot effectivness as

ηCarnot,0 = COP0 ⁄ (Tcon,0 ⁄ (Tcon,0-Teva,0)).

The heat pump COP is computed as the product

COP = ηCarnot,0 COPCarnot ηPL,

where COPCarnot is the Carnot efficiency and ηPL is a polynomial in the heating part load ratio yPL that can be used to take into account a change in COP at part load conditions. This polynomial has the form

ηPL = a1 + a2 yPL + a3 yPL2 + ...

where the coefficients ai are declared by the parameter a.

On the Dynamics tag, the model can be parametrized to compute a transient or steady-state response. The transient response of the model is computed using a first order differential equation for the evaporator and condenser fluid volumes. The heat pump outlet temperatures are equal to the temperatures of these lumped volumes.

Typical use and important parameters

When using this component, make sure that the evaporator and the condenser have sufficient mass flow rate. Based on the mass flow rates, the compressor power, temperature difference and the efficiencies, the model computes how much heat will be added to the condenser and removed at the evaporator. If the mass flow rates are too small, very high temperature differences can result.

The condenser heat flow rate QCon_flow_nominal is used to assign the default value for the mass flow rates, which are used for the pressure drop calculations. It is also used to compute the part load efficiency. Hence, make sure that QCon_flow_nominal is set to a reasonable value.

The maximum heating capacity is set by the parameter QCon_flow_max, which is by default set to infinity.

The coefficient of performance depends on the evaporator and condenser leaving temperature since otherwise the second law of thermodynamics may be violated.

Notes

For a similar model that can be used as a chiller, see Buildings.Fluid.Chillers.Carnot_y.

Extends from Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_y (Partial chiller model with performance curve adjusted based on Carnot efficiency).

Parameters

TypeNameDefaultDescription
replaceable package Medium1PartialMediumMedium 1 in the component
replaceable package Medium2PartialMediumMedium 2 in the component
Nominal condition
MassFlowRatem1_flow_nominalQCon_flow_nominal/cp1_defaul...Nominal mass flow rate [kg/s]
MassFlowRatem2_flow_nominalQEva_flow_nominal/cp2_defaul...Nominal mass flow rate [kg/s]
TemperatureDifferencedTEva_nominal-10Temperature difference evaporator outlet-inlet [K]
TemperatureDifferencedTCon_nominal10Temperature difference condenser outlet-inlet [K]
Pressuredp1_nominal Pressure difference over condenser [Pa]
Pressuredp2_nominal Pressure difference over evaporator [Pa]
PowerP_nominal Nominal compressor power (at y=1) [W]
Efficiency
Booleanuse_eta_Carnot_nominaltrueSet to true to use Carnot effectiveness etaCarnot_nominal rather than COP_nominal
RealetaCarnot_nominalCOP_nominal/(TUseAct_nominal...Carnot effectiveness (=COP/COP_Carnot) used if use_eta_Carnot_nominal = true [1]
RealCOP_nominaletaCarnot_nominal*TUseAct_no...Coefficient of performance at TEva_nominal and TCon_nominal, used if use_eta_Carnot_nominal = false [1]
TemperatureTCon_nominal303.15Condenser temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K]
TemperatureTEva_nominal278.15Evaporator temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K]
Reala[:]{1}Coefficients for efficiency curve (need p(a=a, yPL=1)=1)
TemperatureDifferenceTAppCon_nominalif cp1_default < 1500 then 5...Temperature difference between refrigerant and working fluid outlet in condenser [K]
TemperatureDifferenceTAppEva_nominalif cp2_default < 1500 then 5...Temperature difference between refrigerant and working fluid outlet in evaporator [K]
Assumptions
BooleanallowFlowReversal1true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1
BooleanallowFlowReversal2true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2
Advanced
MassFlowRatem1_flow_small1E-4*abs(m1_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRatem2_flow_small1E-4*abs(m2_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed
Flow resistance
Condenser
Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar [1]
Evaporator
Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar [1]
Dynamics
Condenser
Timetau160Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT1_startMedium1.T_defaultInitial or guess value of set point [K]
Evaporator
Timetau260Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT2_startMedium2.T_defaultInitial or guess value of set point [K]
Evaporator and condenser
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state

Connectors

TypeNameDescription
FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
output RealOutputQCon_flowActual heating heat flow rate added to fluid 1 [W]
output RealOutputPElectric power consumed by compressor [W]
output RealOutputQEva_flowActual cooling heat flow rate removed from fluid 2 [W]
input RealInputyPart load ratio of compressor [1]

Modelica definition

model Carnot_y "Reversible heat pump with performance curve adjusted based on Carnot efficiency" extends Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_y( final COP_is_for_cooling = false); initial equation assert(COP_nominal > 1, "The nominal COP of a heat pump must be bigger than one."); end Carnot_y;

Buildings.Fluid.HeatPumps.ReciprocatingWaterToWater Buildings.Fluid.HeatPumps.ReciprocatingWaterToWater

Model for a reciprocating water to water heat pump

Buildings.Fluid.HeatPumps.ReciprocatingWaterToWater

Information

Model for a water to water heat pump with a reciprocating compressor, as described in Jin (2002). The thermodynamic heat pump cycle is represented below.

image

The rate of heat transferred to the evaporator is given by:

Eva = ṁref ( hVap(TEva) - hLiq(TCon) ).

The power consumed by the compressor is given by a linear efficiency relation:

P = PTheoretical / η + PLoss,constant.

Heat transfer in the evaporator and condenser is calculated using an ε-NTU method, assuming constant refrigerant temperature and constant heat transfer coefficient between fluid and refrigerant.

Variable speed is acheived by multiplying the full load piston displacement by the normalized compressor speed. The power and heat transfer rates are forced to zero if the resulting heat pump state has higher evaporating pressure than condensing pressure.

Options

Parameters TConMax and TEvaMin may be used to set an upper or lower bound for the condenser and evaporator. The compressor is disabled when these conditions are not satisfied, or when the evaporator temperature is larger than the condenser temperature. This mimics the temperature protection of heat pumps and moreover it avoids non-converging algebraic loops of equations, or freezing of evaporator medium. This option can be disabled by setting enable_temperature_protection = false.

Assumptions and limitations

The compression process is assumed isentropic. The thermal energy of superheating is ignored in the evaluation of the heat transferred to the refrigerant in the evaporator. There is no supercooling.

References

H. Jin. Parameter estimation based models of water source heat pumps. PhD Thesis. Oklahoma State University. Stillwater, Oklahoma, USA. 2012.

Extends from Buildings.Fluid.HeatPumps.BaseClasses.PartialWaterToWater (Partial model for water to water heat pumps and chillers).

Parameters

TypeNameDefaultDescription
replaceable package Medium1PartialMediumMedium 1 in the component
replaceable package Medium2PartialMediumMedium 2 in the component
replaceable package refR410ARefrigerant in the component
Booleanenable_variable_speedtrueSet to true to allow modulating of compressor speed
Realscaling_factor1.0Scaling factor for heat pump capacity
ThermalConductanceUAConper.UACon*scaling_factorThermal conductance of condenser [W/K]
ThermalConductanceUAEvaper.UAEva*scaling_factorThermal conductance of evaporator [W/K]
Genericper Heat pump performance data
Nominal condition
MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]
MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]
PressureDifferencedp1_nominal Pressure difference [Pa]
PressureDifferencedp2_nominal Pressure difference [Pa]
Temperature protection
Booleanenable_temperature_protectiontrueEnable temperature protection
TemperatureTConMaxref.TCri - 5Upper bound for condenser temperature [K]
TemperatureTEvaMin275.15Lower bound for evaporator temperature [K]
RealdTHys5Hysteresis interval width [K]
Assumptions
BooleanallowFlowReversal1true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1
BooleanallowFlowReversal2true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2
Advanced
MassFlowRatem1_flow_small1E-4*abs(m1_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRatem2_flow_small1E-4*abs(m2_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed
Flow resistance
Medium 1
Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Condenser
Timetau160Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT1_startMedium1.T_defaultInitial or guess value of set point [K]
Evaporator
Timetau260Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT2_startMedium2.T_defaultInitial or guess value of set point [K]
Evaporator and condenser
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state

Connectors

TypeNameDescription
FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
output BooleanOutputerrLowPreif true, compressor disabled since evaporator temperature is above upper bound
output BooleanOutputerrHigPreif true, compressor disabled since condenser temperature is below lower bound
output BooleanOutputerrNegTemDifif true, compressor disabled since condenser temperature is below evaporator temperature
input RealInputyModulating signal for compressor frequency, equal to 1 at full load condition [1]
input IntegerInputstageCurrent stage of the heat pump, equal to 1 at full load condition
output RealOutputQCon_flowActual heating heat flow rate added to fluid 1 [W]
output RealOutputPElectric power consumed by compressor [W]
output RealOutputQEva_flowActual cooling heat flow rate removed from fluid 2 [W]

Modelica definition

model ReciprocatingWaterToWater "Model for a reciprocating water to water heat pump" extends Buildings.Fluid.HeatPumps.BaseClasses.PartialWaterToWater( final UAEva=per.UAEva * scaling_factor, final UACon=per.UACon * scaling_factor, redeclare HeatPumps.Compressors.ReciprocatingCompressor com( redeclare final package ref=ref, pisDis=per.pisDis * scaling_factor, cleFac=per.cleFac, etaEle=per.etaEle, PLos=per.PLos * scaling_factor, pDro=per.pDro, dTSup=per.dTSup)); parameter Data.ReciprocatingWaterToWater.Generic per "Heat pump performance data"; end ReciprocatingWaterToWater;

Buildings.Fluid.HeatPumps.ScrollWaterToWater Buildings.Fluid.HeatPumps.ScrollWaterToWater

Model for a scroll water to water heat pump

Buildings.Fluid.HeatPumps.ScrollWaterToWater

Information

Model for a water to water heat pump with a scroll compressor, as described in Jin (2002). The thermodynamic heat pump cycle is represented below.

image

The rate of heat transferred to the evaporator is given by:

Eva = ṁref ( hVap(TEva) - hLiq(TCon) ).

The power consumed by the compressor is given by a linear efficiency relation:

P = PTheoretical / η + PLoss,constant.

Heat transfer in the evaporator and condenser is calculated using an ε-NTU method, assuming constant refrigerant temperature and constant heat transfer coefficient between fluid and refrigerant.

Variable speed is achieved by multiplying the full load suction volume flow rate by the normalized compressor speed. The power and heat transfer rates are forced to zero if the resulting heat pump state has higher evaporating pressure than condensing pressure.

The model parameters are obtained by calibration of the heat pump model to manufacturer performance data. Calibrated model parameters for various heat pumps from different manufacturers are found in Buildings.Fluid.HeatPumps.Data.ScrollWaterToWater. The calibrated model is located in Buildings.Fluid.HeatPumps.Calibration.ScrollWaterToWater.

Options

Parameters TConMax and TEvaMin may be used to set an upper or lower bound for the condenser and evaporator. The compressor is disabled when these conditions are not satisfied, or when the evaporator temperature is larger than the condenser temperature. This mimics the temperature protection of heat pumps and moreover it avoids non-converging algebraic loops of equations, or freezing of evaporator medium. This option can be disabled by setting enable_temperature_protection = false.

Assumptions and limitations

The compression process is assumed isentropic. The thermal energy of superheating is ignored in the evaluation of the heat transferred to the refrigerant in the evaporator. There is no supercooling.

References

H. Jin. Parameter estimation based models of water source heat pumps. PhD Thesis. Oklahoma State University. Stillwater, Oklahoma, USA. 2012.

Extends from Buildings.Fluid.HeatPumps.BaseClasses.PartialWaterToWater (Partial model for water to water heat pumps and chillers).

Parameters

TypeNameDefaultDescription
replaceable package Medium1PartialMediumMedium 1 in the component
replaceable package Medium2PartialMediumMedium 2 in the component
replaceable package refR410ARefrigerant in the component
Booleanenable_variable_speedtrueSet to true to allow modulating of compressor speed
Realscaling_factor1.0Scaling factor for heat pump capacity
ThermalConductanceUACondatHeaPum.UACon*scaling_factorThermal conductance of condenser [W/K]
ThermalConductanceUAEvadatHeaPum.UAEva*scaling_factorThermal conductance of evaporator [W/K]
GenericdatHeaPum Heat pump data
Nominal condition
MassFlowRatem1_flow_nominal Nominal mass flow rate [kg/s]
MassFlowRatem2_flow_nominal Nominal mass flow rate [kg/s]
PressureDifferencedp1_nominal Pressure difference [Pa]
PressureDifferencedp2_nominal Pressure difference [Pa]
Temperature protection
Booleanenable_temperature_protectiontrueEnable temperature protection
TemperatureTConMaxref.TCri - 5Upper bound for condenser temperature [K]
TemperatureTEvaMin275.15Lower bound for evaporator temperature [K]
RealdTHys5Hysteresis interval width [K]
Assumptions
BooleanallowFlowReversal1true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1
BooleanallowFlowReversal2true= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2
Advanced
MassFlowRatem1_flow_small1E-4*abs(m1_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRatem2_flow_small1E-4*abs(m2_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed
Flow resistance
Medium 1
Booleanfrom_dp1false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance1false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM10.1Fraction of nominal flow rate where flow transitions to laminar
Medium 2
Booleanfrom_dp2false= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistance2false= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM20.1Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Condenser
Timetau160Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT1_startMedium1.T_defaultInitial or guess value of set point [K]
Evaporator
Timetau260Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s]
TemperatureT2_startMedium2.T_defaultInitial or guess value of set point [K]
Evaporator and condenser
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state

Connectors

TypeNameDescription
FluidPort_aport_a1Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_bport_b1Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_aport_a2Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_bport_b2Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
output BooleanOutputerrLowPreif true, compressor disabled since evaporator temperature is above upper bound
output BooleanOutputerrHigPreif true, compressor disabled since condenser temperature is below lower bound
output BooleanOutputerrNegTemDifif true, compressor disabled since condenser temperature is below evaporator temperature
input RealInputyModulating signal for compressor frequency, equal to 1 at full load condition [1]
input IntegerInputstageCurrent stage of the heat pump, equal to 1 at full load condition
output RealOutputQCon_flowActual heating heat flow rate added to fluid 1 [W]
output RealOutputPElectric power consumed by compressor [W]
output RealOutputQEva_flowActual cooling heat flow rate removed from fluid 2 [W]

Modelica definition

model ScrollWaterToWater "Model for a scroll water to water heat pump" extends Buildings.Fluid.HeatPumps.BaseClasses.PartialWaterToWater( final UAEva=datHeaPum.UAEva*scaling_factor, final UACon=datHeaPum.UACon*scaling_factor, redeclare HeatPumps.Compressors.ScrollCompressor com( redeclare final package ref = ref, final volRat=datHeaPum.volRat, final V_flow_nominal=datHeaPum.V_flow_nominal*scaling_factor, final leaCoe=datHeaPum.leaCoe*scaling_factor, final etaEle=datHeaPum.etaEle, final PLos=datHeaPum.PLos*scaling_factor, final dTSup=datHeaPum.dTSup)); parameter Buildings.Fluid.HeatPumps.Data.ScrollWaterToWater.Generic datHeaPum "Heat pump data"; end ScrollWaterToWater;