Buildings.Fluid.Chillers.BaseClasses
Package with base classes for Buildings.Fluid.Chillers
Information
This package contains base classes that are used to construct the models in Buildings.Fluid.Chillers.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
Package Content
| Name | Description |
|---|---|
 AbsorptionIndirectSteam
|
Absorption indirect chiller performance curve method |
 Carnot
|
|
| PartialCarnot_T
|
Partial model for chiller with performance curve adjusted based on Carnot efficiency |
 PartialCarnot_y
|
Partial chiller model with performance curve adjusted based on Carnot efficiency |
 PartialElectric
|
Partial model for electric chiller based on the model in DOE-2, CoolTools and EnergyPlus |
 warnIfPerformanceOutOfBounds
|
Function that checks the performance and writes a warning if it is outside of 0.9 to 1.1 |
Buildings.Fluid.Chillers.BaseClasses.AbsorptionIndirectSteam
Absorption indirect chiller performance curve method
Information
Block that computes the performance for the model Buildings.Fluid.Chillers.AbsorptionIndirectSteam. See Buildings.Fluid.Chillers.AbsorptionIndirectSteam for a description of this model.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Generic | per | Performance data | |
| HeatFlowRate | Q_flow_small | Small value for heat flow rate or power, used to avoid division by zero [W] |
Connectors
| Type | Name | Description |
|---|---|---|
| input BooleanInput | on | Set to true to enable the absorption chiller |
| input RealInput | TConEnt | Condenser entering water temperature [K] |
| input RealInput | TEvaLvg | Evaporator leaving water temperature [K] |
| input RealInput | QEva_flow_set | Evaporator setpoint heat flow rate [W] |
| output RealOutput | QCon_flow | Condenser heat flow rate [W] |
| output RealOutput | QEva_flow | Evaporator heat flow rate [W] |
| output RealOutput | QGen_flow | Required generator heat flow rate [W] |
| output RealOutput | P | Pump power [W] |
| output RealOutput | PLR | Part load ratio [1] |
| output RealOutput | CR | Cycling ratio [1] |
Modelica definition
block AbsorptionIndirectSteam
"Absorption indirect chiller performance curve method"
extends Modelica.Blocks.Icons.Block;
parameter Buildings.Fluid.Chillers.Data.AbsorptionIndirectSteam.Generic per
"Performance data";
parameter Modelica.Units.SI.HeatFlowRate Q_flow_small
"Small value for heat flow rate or power, used to avoid division by zero";
Modelica.Blocks.Interfaces.BooleanInput on
"Set to true to enable the absorption chiller";
Modelica.Blocks.Interfaces.RealInput TConEnt(
final unit="K",
displayUnit="degC")
"Condenser entering water temperature";
Modelica.Blocks.Interfaces.RealInput TEvaLvg(
final unit="K",
displayUnit="degC")
"Evaporator leaving water temperature";
Modelica.Blocks.Interfaces.RealInput QEva_flow_set(final unit="W")
"Evaporator setpoint heat flow rate";
Modelica.Blocks.Interfaces.RealOutput QCon_flow(final unit="W")
"Condenser heat flow rate ";
Modelica.Blocks.Interfaces.RealOutput QEva_flow(final unit="W")
"Evaporator heat flow rate";
Modelica.Blocks.Interfaces.RealOutput QGen_flow(final unit="W")
"Required generator heat flow rate";
Modelica.Blocks.Interfaces.RealOutput P(final unit="W")
"Pump power";
Modelica.Blocks.Interfaces.RealOutput PLR(min=0, final unit="1")
"Part load ratio";
Modelica.Blocks.Interfaces.RealOutput CR(min=0, final unit="1")
"Cycling ratio";
Modelica.Units.SI.Efficiency genHIR
"Ratio of the generator heat input to chiller operating capacity";
Modelica.Units.SI.Efficiency EIRP(min=0)
"Ratio of the actual absorber pumping power to the nominal pumping power";
Real capFunEva(min=0)
"Evaporator capacity factor function of temperature curve";
Real capFunCon(min=0)
"Condenser capacity factor function of temperature curve";
Real genConT(min=0)
"Heat input modifier based on the generator input temperature";
Real genEvaT(min=0)
"Heat input modifier based on the evaporator outlet temperature";
Modelica.Units.SI.HeatFlowRate QEva_flow_ava
"Cooling capacity available at the evaporator";
protected
Modelica.Units.NonSI.Temperature_degC TConEnt_degC
"Condenser entering water temperature in degC";
Modelica.Units.NonSI.Temperature_degC TEvaLvg_degC
"Evaporator leaving water temperature in degC";
initial equation
assert(per.QEva_flow_nominal < 0,
"In " + getInstanceName() + ": Parameter QEva_flow_nominal must be smaller than zero.");
assert(Q_flow_small > 0,
"In " + getInstanceName() + ": Parameter Q_flow_small must be larger than zero.");
equation
TConEnt_degC=Modelica.Units.Conversions.to_degC(TConEnt);
TEvaLvg_degC=Modelica.Units.Conversions.to_degC(TEvaLvg);
if on then
capFunEva = Buildings.Utilities.Math.Functions.smoothMax(
x1 = 1E-6,
x2 = Buildings.Utilities.Math.Functions.polynomial(x=TEvaLvg_degC, a=per.capFunEva),
deltaX = Q_flow_small);
capFunCon = Buildings.Utilities.Math.Functions.smoothMax(
x1 = 1E-6,
x2 = Buildings.Utilities.Math.Functions.polynomial(x=TConEnt_degC, a=per.capFunCon),
deltaX = Q_flow_small);
QEva_flow_ava = per.QEva_flow_nominal*capFunEva*capFunCon;
QEva_flow = Buildings.Utilities.Math.Functions.smoothMax(
x1 = QEva_flow_set,
x2 = QEva_flow_ava,
deltaX = Q_flow_small);
PLR =Buildings.Utilities.Math.Functions.smoothMin(
x1=QEva_flow_set/(QEva_flow_ava - Q_flow_small),
x2=per.PLRMax,
deltaX=per.PLRMax/100);
genHIR = per.genHIR[1]+ per.genHIR[2]*PLR+per.genHIR[3]*PLR^2+per.genHIR[4]*PLR^3;
genConT = Buildings.Utilities.Math.Functions.polynomial(x=TConEnt_degC, a=per.genConT);
genEvaT = Buildings.Utilities.Math.Functions.polynomial(x=TEvaLvg_degC, a=per.genEvaT);
EIRP = Buildings.Utilities.Math.Functions.polynomial(x=PLR, a=per.EIRP);
CR = Buildings.Utilities.Math.Functions.smoothMin(
x1 = PLR/per.PLRMin,
x2 = 1,
deltaX = 0.001);
QGen_flow = -QEva_flow_ava * genHIR * genConT * genEvaT * CR;
P = EIRP * per.P_nominal * CR;
QCon_flow = -QEva_flow + QGen_flow + P;
else
capFunEva = 0;
capFunCon = 0;
QEva_flow_ava = 0;
QEva_flow = 0;
PLR = 0;
genHIR = per.genHIR[1];
genConT = 1;
genEvaT = 1;
EIRP = 0;
CR = 0;
QGen_flow = 0;
P = 0;
QCon_flow = 0;
end if;
end AbsorptionIndirectSteam;
Buildings.Fluid.Chillers.BaseClasses.Carnot
Information
This is the base class for the Carnot chiller and the Carnot heat pump whose coefficient of performance COP changes with temperatures in the same way as the Carnot efficiency changes.
Set use_eta_Carnot_nominal=true to specify directly
the Carnot effectiveness ηCarnot,0,
in which case the value of the parameter COP_nominal
will not affect the simulation.
If use_eta_Carnot_nominal=false, the model will use
the value of the parameter COP_nominal
together with the specified nominal temperatures
to compute the Carnot effectiveness as
ηCarnot,0 = COP0 ⁄ (Tuse,0 ⁄ (Tcon,0 + Tapp,con,0 - (Teva,0-Tapp,eva,0))),
where
Teva,0 is the evaporator temperature,
Tcon,0 is the condenser temperature,
Tapp,eva,0 is the evaporator approach temperature,
Tapp,con,0 is the condenser approach temperature, and
Tuse,0 is the temperature of the the useful heat.
If COP_is_for_cooling=true,
then Tuse,0 is the condenser temperature of a heat pump plus the approach temperature,
otherwise it is the evaporator temperature minus the approach temperature of a chiller.
The COP is computed as the product
COP = ηCarnot,0 COPCarnot ηPL,
where COPCarnot is the Carnot efficiency and ηPL is the part load efficiency, expressed using a polynomial. This polynomial has the form
ηPL = a1 + a2 y + a3 y2 + ...,
where y ∈ [0, 1] is
either the part load for cooling in case of a chiller, or the part load of heating in
case of a heat pump, and the coefficients ai
are declared by the parameter a.
Implementation
To make this base class applicable to chiller or heat pumps, it uses
the boolean constant COP_is_for_cooling.
Depending on its value, the equations for the coefficient of performance
and the part load ratio are set up.
Extends from Buildings.Fluid.Interfaces.PartialFourPortInterface (Partial model transporting fluid between two ports without storing mass or energy).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium1 | PartialMedium | Medium 1 in the component | |
| replaceable package Medium2 | PartialMedium | Medium 2 in the component | |
| Nominal condition | |||
| MassFlowRate | m1_flow_nominal | QCon_flow_nominal/cp1_defaul... | Nominal mass flow rate [kg/s] |
| MassFlowRate | m2_flow_nominal | QEva_flow_nominal/cp2_defaul... | Nominal mass flow rate [kg/s] |
| HeatFlowRate | QEva_flow_nominal | Nominal cooling heat flow rate (QEva_flow_nominal < 0) [W] | |
| HeatFlowRate | QCon_flow_nominal | Nominal heating flow rate [W] | |
| TemperatureDifference | dTEva_nominal | -10 | Temperature difference evaporator outlet-inlet [K] |
| TemperatureDifference | dTCon_nominal | 10 | Temperature difference condenser outlet-inlet [K] |
| Pressure | dp1_nominal | Pressure difference over condenser [Pa] | |
| Pressure | dp2_nominal | Pressure difference over evaporator [Pa] | |
| Efficiency | |||
| Boolean | use_eta_Carnot_nominal | true | Set to true to use Carnot effectiveness etaCarnot_nominal rather than COP_nominal |
| Real | etaCarnot_nominal | 0.3 | Carnot effectiveness (=COP/COP_Carnot) used during simulation if use_eta_Carnot_nominal = true [1] |
| Real | COP_nominal | etaCarnot_nominal*TUseAct_no... | Coefficient of performance at TEva_nominal and TCon_nominal, used during simulation if use_eta_Carnot_nominal = false [1] |
| Temperature | TCon_nominal | 303.15 | Condenser temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K] |
| Temperature | TEva_nominal | 278.15 | Evaporator temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K] |
| Real | a[:] | {1} | Coefficients for efficiency curve (need p(a=a, yPL=1)=1) |
| TemperatureDifference | TAppCon_nominal | if cp1_default < 1500 then 5... | Temperature difference between refrigerant and working fluid outlet in condenser [K] |
| TemperatureDifference | TAppEva_nominal | if cp2_default < 1500 then 5... | Temperature difference between refrigerant and working fluid outlet in evaporator [K] |
| Assumptions | |||
| Boolean | allowFlowReversal1 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1 |
| Boolean | allowFlowReversal2 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2 |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Condenser | |||
| Boolean | from_dp1 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance1 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM1 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar [1] |
| Evaporator | |||
| Boolean | from_dp2 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance2 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM2 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar [1] |
| Dynamics | |||
| Condenser | |||
| Time | tau1 | 60 | Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Temperature | T1_start | Medium1.T_default | Initial or guess value of set point [K] |
| Evaporator | |||
| Time | tau2 | 60 | Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Temperature | T2_start | Medium2.T_default | Initial or guess value of set point [K] |
| Evaporator and condenser | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| output RealOutput | QCon_flow | Actual heating heat flow rate added to fluid 1 [W] |
| output RealOutput | P | Electric power consumed by compressor [W] |
| output RealOutput | QEva_flow | Actual cooling heat flow rate removed from fluid 2 [W] |
Modelica definition
partial model Carnot
extends Buildings.Fluid.Interfaces.PartialFourPortInterface(
m1_flow_nominal = QCon_flow_nominal/cp1_default/dTCon_nominal,
m2_flow_nominal = QEva_flow_nominal/cp2_default/dTEva_nominal);
constant Boolean homotopyInitialization = true "= true, use homotopy method";
parameter Modelica.Units.SI.HeatFlowRate QEva_flow_nominal(max=0)
"Nominal cooling heat flow rate (QEva_flow_nominal < 0)";
parameter Modelica.Units.SI.HeatFlowRate QCon_flow_nominal(min=0)
"Nominal heating flow rate";
parameter Modelica.Units.SI.TemperatureDifference dTEva_nominal(final max=0)
= -10 "Temperature difference evaporator outlet-inlet";
parameter Modelica.Units.SI.TemperatureDifference dTCon_nominal(final min=0)
= 10 "Temperature difference condenser outlet-inlet";
// Efficiency
parameter Boolean use_eta_Carnot_nominal = true
"Set to true to use Carnot effectiveness etaCarnot_nominal rather than COP_nominal";
parameter Real etaCarnot_nominal(unit="1") = 0.3
"Carnot effectiveness (=COP/COP_Carnot) used during simulation if use_eta_Carnot_nominal = true";
parameter Real COP_nominal(unit="1") = etaCarnot_nominal*TUseAct_nominal/
(TCon_nominal+TAppCon_nominal - (TEva_nominal-TAppEva_nominal))
"Coefficient of performance at TEva_nominal and TCon_nominal, used during simulation if use_eta_Carnot_nominal = false";
parameter Modelica.Units.SI.Temperature TCon_nominal=303.15
"Condenser temperature used to compute COP_nominal if use_eta_Carnot_nominal=false";
parameter Modelica.Units.SI.Temperature TEva_nominal=278.15
"Evaporator temperature used to compute COP_nominal if use_eta_Carnot_nominal=false";
parameter Real a[:] = {1}
"Coefficients for efficiency curve (need p(a=a, yPL=1)=1)";
parameter Modelica.Units.SI.Pressure dp1_nominal(displayUnit="Pa")
"Pressure difference over condenser";
parameter Modelica.Units.SI.Pressure dp2_nominal(displayUnit="Pa")
"Pressure difference over evaporator";
parameter Modelica.Units.SI.TemperatureDifference TAppCon_nominal(min=0) =
if cp1_default < 1500 then 5 else 2
"Temperature difference between refrigerant and working fluid outlet in condenser";
parameter Modelica.Units.SI.TemperatureDifference TAppEva_nominal(min=0) =
if cp2_default < 1500 then 5 else 2
"Temperature difference between refrigerant and working fluid outlet in evaporator";
parameter Boolean from_dp1=false
"= true, use m_flow = f(dp) else dp = f(m_flow)";
parameter Boolean from_dp2=false
"= true, use m_flow = f(dp) else dp = f(m_flow)";
parameter Boolean linearizeFlowResistance1=false
"= true, use linear relation between m_flow and dp for any flow rate";
parameter Boolean linearizeFlowResistance2=false
"= true, use linear relation between m_flow and dp for any flow rate";
parameter Real deltaM1(final unit="1")=0.1
"Fraction of nominal flow rate where flow transitions to laminar";
parameter Real deltaM2(final unit="1")=0.1
"Fraction of nominal flow rate where flow transitions to laminar";
parameter Modelica.Units.SI.Time tau1=60
"Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState)";
parameter Modelica.Units.SI.Time tau2=60
"Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState)";
parameter Modelica.Units.SI.Temperature T1_start=Medium1.T_default
"Initial or guess value of set point";
parameter Modelica.Units.SI.Temperature T2_start=Medium2.T_default
"Initial or guess value of set point";
parameter Modelica.Fluid.Types.Dynamics energyDynamics=
Modelica.Fluid.Types.Dynamics.SteadyState "Type of energy balance: dynamic (3 initialization options) or steady state";
Modelica.Blocks.Interfaces.RealOutput QCon_flow(
final quantity="HeatFlowRate",
final unit="W") "Actual heating heat flow rate added to fluid 1";
Modelica.Blocks.Interfaces.RealOutput P(
final quantity="Power",
final unit="W") "Electric power consumed by compressor";
Modelica.Blocks.Interfaces.RealOutput QEva_flow(
final quantity="HeatFlowRate",
final unit="W") "Actual cooling heat flow rate removed from fluid 2";
Real yPL(final unit="1", min=0) = if COP_is_for_cooling
then QEva_flow/QEva_flow_nominal
else QCon_flow/QCon_flow_nominal "Part load ratio";
Real etaPL(final unit = "1")=
if evaluate_etaPL
then Buildings.Utilities.Math.Functions.polynomial(a=a, x=yPL)
else 1
"Efficiency due to part load (etaPL(yPL=1)=1)";
Real COP(min=0, final unit="1") = etaCarnot_nominal_internal * COPCar * etaPL
"Coefficient of performance";
Real COPCar(min=0) = TUseAct/Buildings.Utilities.Math.Functions.smoothMax(
x1=1,
x2=TConAct - TEvaAct,
deltaX=0.25) "Carnot efficiency";
Modelica.Units.SI.Temperature TConAct(start=TCon_nominal + TAppCon_nominal)
= Medium1.temperature(staB1) + QCon_flow/QCon_flow_nominal*TAppCon_nominal
"Condenser temperature used to compute efficiency, taking into account pinch temperature between fluid and refrigerant";
Modelica.Units.SI.Temperature TEvaAct(start=TEva_nominal - TAppEva_nominal)
= Medium2.temperature(staB2) - QEva_flow/QEva_flow_nominal*TAppEva_nominal
"Evaporator temperature used to compute efficiency, taking into account pinch temperature between fluid and refrigerant";
protected
constant Boolean COP_is_for_cooling
"Set to true if the specified COP is for cooling";
parameter Real etaCarnot_nominal_internal(unit="1")=
if use_eta_Carnot_nominal
then etaCarnot_nominal
else COP_nominal/
(TUseAct_nominal / (TCon_nominal + TAppCon_nominal - (TEva_nominal - TAppEva_nominal)))
"Carnot effectiveness (=COP/COP_Carnot) used to compute COP";
// For Carnot_y, computing etaPL = f(yPL) introduces a nonlinear equation.
// The parameter below avoids this if a = {1}.
final parameter Boolean evaluate_etaPL=
not ((size(a, 1) == 1 and abs(a[1] - 1) < Modelica.Constants.eps))
"Flag, true if etaPL should be computed as it depends on yPL";
final parameter Modelica.Units.SI.Temperature TUseAct_nominal=if
COP_is_for_cooling then TEva_nominal - TAppEva_nominal else TCon_nominal
+ TAppCon_nominal
"Nominal evaporator temperature for chiller or condenser temperature for heat pump, taking into account pinch temperature between fluid and refrigerant";
Modelica.Units.SI.Temperature TUseAct=if COP_is_for_cooling then TEvaAct
else TConAct
"Temperature of useful heat (evaporator for chiller, condenser for heat pump), taking into account pinch temperature between fluid and refrigerant";
final parameter Modelica.Units.SI.SpecificHeatCapacity cp1_default=
Medium1.specificHeatCapacityCp(Medium1.setState_pTX(
p=Medium1.p_default,
T=Medium1.T_default,
X=Medium1.X_default))
"Specific heat capacity of medium 1 at default medium state";
final parameter Modelica.Units.SI.SpecificHeatCapacity cp2_default=
Medium2.specificHeatCapacityCp(Medium2.setState_pTX(
p=Medium2.p_default,
T=Medium2.T_default,
X=Medium2.X_default))
"Specific heat capacity of medium 2 at default medium state";
Medium1.ThermodynamicState staA1 = Medium1.setState_phX(
port_a1.p,
inStream(port_a1.h_outflow),
inStream(port_a1.Xi_outflow)) "Medium properties in port_a1";
Medium1.ThermodynamicState staB1 = Medium1.setState_phX(
port_b1.p,
port_b1.h_outflow,
port_b1.Xi_outflow) "Medium properties in port_b1";
Medium2.ThermodynamicState staA2 = Medium2.setState_phX(
port_a2.p,
inStream(port_a2.h_outflow),
inStream(port_a2.Xi_outflow)) "Medium properties in port_a2";
Medium2.ThermodynamicState staB2 = Medium2.setState_phX(
port_b2.p,
port_b2.h_outflow,
port_b2.Xi_outflow) "Medium properties in port_b2";
replaceable Interfaces.PartialTwoPortInterface con
constrainedby Interfaces.PartialTwoPortInterface(
redeclare final package Medium = Medium1,
final allowFlowReversal=allowFlowReversal1,
final m_flow_nominal=m1_flow_nominal,
final m_flow_small=m1_flow_small,
final show_T=false) "Condenser";
replaceable Interfaces.PartialTwoPortInterface eva
constrainedby Interfaces.PartialTwoPortInterface(
redeclare final package Medium = Medium2,
final allowFlowReversal=allowFlowReversal2,
final m_flow_nominal=m2_flow_nominal,
final m_flow_small=m2_flow_small,
final show_T=false) "Evaporator";
initial equation
assert(dTEva_nominal < 0,
"Parameter dTEva_nominal must be negative.");
assert(dTCon_nominal > 0,
"Parameter dTCon_nominal must be positive.");
assert(abs(Buildings.Utilities.Math.Functions.polynomial(
a=a, x=1)-1) < 0.01, "Efficiency curve is wrong. Need etaPL(y=1)=1.");
assert(etaCarnot_nominal_internal < 1, "Parameters lead to etaCarnot_nominal > 1. Check parameters.");
assert(homotopyInitialization, "In " + getInstanceName() +
": The constant homotopyInitialization has been modified from its default value. This constant will be removed in future releases.",
level = AssertionLevel.warning);
equation
connect(port_a2, eva.port_a);
connect(eva.port_b, port_b2);
connect(port_a1, con.port_a);
connect(con.port_b, port_b1);
end Carnot;
Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_T
Partial model for chiller with performance curve adjusted based on Carnot efficiency
Information
This is a partial model of a chiller whose coefficient of performance (COP) changes with temperatures in the same way as the Carnot efficiency changes. This base class is used for the Carnot chiller and Carnot heat pump that uses the compressor part load ratio as the control signal.
Extends from Buildings.Fluid.Chillers.BaseClasses.Carnot.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium1 | PartialMedium | Medium 1 in the component | |
| replaceable package Medium2 | PartialMedium | Medium 2 in the component | |
| Nominal condition | |||
| MassFlowRate | m1_flow_nominal | QCon_flow_nominal/cp1_defaul... | Nominal mass flow rate [kg/s] |
| MassFlowRate | m2_flow_nominal | QEva_flow_nominal/cp2_defaul... | Nominal mass flow rate [kg/s] |
| HeatFlowRate | QEva_flow_nominal | Nominal cooling heat flow rate (QEva_flow_nominal < 0) [W] | |
| HeatFlowRate | QCon_flow_nominal | Nominal heating flow rate [W] | |
| TemperatureDifference | dTEva_nominal | -10 | Temperature difference evaporator outlet-inlet [K] |
| TemperatureDifference | dTCon_nominal | 10 | Temperature difference condenser outlet-inlet [K] |
| Pressure | dp1_nominal | Pressure difference over condenser [Pa] | |
| Pressure | dp2_nominal | Pressure difference over evaporator [Pa] | |
| Efficiency | |||
| Boolean | use_eta_Carnot_nominal | true | Set to true to use Carnot effectiveness etaCarnot_nominal rather than COP_nominal |
| Real | etaCarnot_nominal | 0.3 | Carnot effectiveness (=COP/COP_Carnot) used during simulation if use_eta_Carnot_nominal = true [1] |
| Real | COP_nominal | etaCarnot_nominal*TUseAct_no... | Coefficient of performance at TEva_nominal and TCon_nominal, used during simulation if use_eta_Carnot_nominal = false [1] |
| Temperature | TCon_nominal | 303.15 | Condenser temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K] |
| Temperature | TEva_nominal | 278.15 | Evaporator temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K] |
| Real | a[:] | {1} | Coefficients for efficiency curve (need p(a=a, yPL=1)=1) |
| TemperatureDifference | TAppCon_nominal | if cp1_default < 1500 then 5... | Temperature difference between refrigerant and working fluid outlet in condenser [K] |
| TemperatureDifference | TAppEva_nominal | if cp2_default < 1500 then 5... | Temperature difference between refrigerant and working fluid outlet in evaporator [K] |
| Assumptions | |||
| Boolean | allowFlowReversal1 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1 |
| Boolean | allowFlowReversal2 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2 |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Condenser | |||
| Boolean | from_dp1 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance1 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM1 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar [1] |
| Evaporator | |||
| Boolean | from_dp2 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance2 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM2 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar [1] |
| Dynamics | |||
| Condenser | |||
| Time | tau1 | 60 | Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Temperature | T1_start | Medium1.T_default | Initial or guess value of set point [K] |
| Evaporator | |||
| Time | tau2 | 60 | Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Temperature | T2_start | Medium2.T_default | Initial or guess value of set point [K] |
| Evaporator and condenser | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| output RealOutput | QCon_flow | Actual heating heat flow rate added to fluid 1 [W] |
| output RealOutput | P | Electric power consumed by compressor [W] |
| output RealOutput | QEva_flow | Actual cooling heat flow rate removed from fluid 2 [W] |
Modelica definition
partial model PartialCarnot_T
"Partial model for chiller with performance curve adjusted based on Carnot efficiency"
extends Buildings.Fluid.Chillers.BaseClasses.Carnot;
protected
Modelica.Blocks.Sources.RealExpression PEle "Electrical power consumption";
equation
connect(PEle.y, P);
end PartialCarnot_T;
Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_y
Partial chiller model with performance curve adjusted based on Carnot efficiency
Information
This is a partial model of a chiller whose coefficient of performance (COP) changes with temperatures in the same way as the Carnot efficiency changes. This base class is used for the Carnot chiller and Carnot heat pump that uses the leaving fluid temperature as the control signal.
Extends from Carnot.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium1 | PartialMedium | Medium 1 in the component | |
| replaceable package Medium2 | PartialMedium | Medium 2 in the component | |
| Nominal condition | |||
| MassFlowRate | m1_flow_nominal | QCon_flow_nominal/cp1_defaul... | Nominal mass flow rate [kg/s] |
| MassFlowRate | m2_flow_nominal | QEva_flow_nominal/cp2_defaul... | Nominal mass flow rate [kg/s] |
| HeatFlowRate | QEva_flow_nominal | if COP_is_for_cooling then -... | Nominal cooling heat flow rate (QEva_flow_nominal < 0) [W] |
| HeatFlowRate | QCon_flow_nominal | P_nominal - QEva_flow_nominal | Nominal heating flow rate [W] |
| TemperatureDifference | dTEva_nominal | -10 | Temperature difference evaporator outlet-inlet [K] |
| TemperatureDifference | dTCon_nominal | 10 | Temperature difference condenser outlet-inlet [K] |
| Pressure | dp1_nominal | Pressure difference over condenser [Pa] | |
| Pressure | dp2_nominal | Pressure difference over evaporator [Pa] | |
| Power | P_nominal | Nominal compressor power (at y=1) [W] | |
| Efficiency | |||
| Boolean | use_eta_Carnot_nominal | true | Set to true to use Carnot effectiveness etaCarnot_nominal rather than COP_nominal |
| Real | etaCarnot_nominal | 0.3 | Carnot effectiveness (=COP/COP_Carnot) used during simulation if use_eta_Carnot_nominal = true [1] |
| Real | COP_nominal | etaCarnot_nominal*TUseAct_no... | Coefficient of performance at TEva_nominal and TCon_nominal, used during simulation if use_eta_Carnot_nominal = false [1] |
| Temperature | TCon_nominal | 303.15 | Condenser temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K] |
| Temperature | TEva_nominal | 278.15 | Evaporator temperature used to compute COP_nominal if use_eta_Carnot_nominal=false [K] |
| Real | a[:] | {1} | Coefficients for efficiency curve (need p(a=a, yPL=1)=1) |
| TemperatureDifference | TAppCon_nominal | if cp1_default < 1500 then 5... | Temperature difference between refrigerant and working fluid outlet in condenser [K] |
| TemperatureDifference | TAppEva_nominal | if cp2_default < 1500 then 5... | Temperature difference between refrigerant and working fluid outlet in evaporator [K] |
| Assumptions | |||
| Boolean | allowFlowReversal1 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1 |
| Boolean | allowFlowReversal2 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2 |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Condenser | |||
| Boolean | from_dp1 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance1 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM1 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar [1] |
| Evaporator | |||
| Boolean | from_dp2 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance2 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM2 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar [1] |
| Dynamics | |||
| Condenser | |||
| Time | tau1 | 60 | Time constant at nominal flow rate (used if energyDynamics1 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Temperature | T1_start | Medium1.T_default | Initial or guess value of set point [K] |
| Evaporator | |||
| Time | tau2 | 60 | Time constant at nominal flow rate (used if energyDynamics2 <> Modelica.Fluid.Types.Dynamics.SteadyState) [s] |
| Temperature | T2_start | Medium2.T_default | Initial or guess value of set point [K] |
| Evaporator and condenser | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| output RealOutput | QCon_flow | Actual heating heat flow rate added to fluid 1 [W] |
| output RealOutput | P | Electric power consumed by compressor [W] |
| output RealOutput | QEva_flow | Actual cooling heat flow rate removed from fluid 2 [W] |
| input RealInput | y | Part load ratio of compressor [1] |
Modelica definition
partial model PartialCarnot_y
"Partial chiller model with performance curve adjusted based on Carnot efficiency"
extends Carnot(
final QCon_flow_nominal= P_nominal - QEva_flow_nominal,
final QEva_flow_nominal = if COP_is_for_cooling
then -P_nominal * COP_nominal
else -P_nominal * (COP_nominal-1),
redeclare HeatExchangers.HeaterCooler_u con(
final from_dp=from_dp1,
final dp_nominal=dp1_nominal,
final linearizeFlowResistance=linearizeFlowResistance1,
final deltaM=deltaM1,
final tau=tau1,
final T_start=T1_start,
final energyDynamics=energyDynamics,
final homotopyInitialization=homotopyInitialization,
final Q_flow_nominal=QCon_flow_nominal),
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.Units.SI.Power P_nominal(min=0)
"Nominal compressor power (at y=1)";
Modelica.Blocks.Interfaces.RealInput y(min=0, max=1, unit="1")
"Part load ratio of compressor";
protected
Modelica.Units.SI.HeatFlowRate QCon_flow_internal(start=QCon_flow_nominal) =
P - QEva_flow_internal "Condenser heat input";
Modelica.Units.SI.HeatFlowRate QEva_flow_internal(start=QEva_flow_nominal) =
if COP_is_for_cooling then -COP*P else (1 - COP)*P "Evaporator heat input";
Modelica.Blocks.Sources.RealExpression yEva_flow_in(
y=QEva_flow_internal/QEva_flow_nominal)
"Normalized evaporator heat flow rate";
Modelica.Blocks.Sources.RealExpression yCon_flow_in(
y=QCon_flow_internal/QCon_flow_nominal)
"Normalized condenser heat flow rate";
Modelica.Blocks.Math.Gain PEle(final k=P_nominal)
"Electrical power consumption";
equation
connect(PEle.y, P);
connect(PEle.u, y);
connect(yEva_flow_in.y, eva.u);
connect(yCon_flow_in.y, con.u);
connect(con.Q_flow, QCon_flow);
connect(eva.Q_flow, QEva_flow);
end PartialCarnot_y;
Buildings.Fluid.Chillers.BaseClasses.PartialElectric
Partial model for electric chiller based on the model in DOE-2, CoolTools and EnergyPlus
Information
Base class for model of an electric chiller, based on the DOE-2.1 chiller model and the
CoolTools chiller model that are implemented in EnergyPlus as the models
Chiller:Electric:EIR and Chiller:Electric:ReformulatedEIR.
The model takes as an input the set point for the leaving chilled water temperature, which is met if the chiller has sufficient capacity. Thus, the model has a built-in, ideal temperature control. The model has three tests on the part load ratio and the cycling ratio:
-
The test
PLR1 =min(QEva_flow_set/QEva_flow_ava, PLRMax)
ensures that the chiller capacity does not exceed the chiller capacity specified by the parameterPLRMax. -
The test
CR = min(PLR1/per.PRLMin, 1.0)
computes a cycling ratio. This ratio expresses the fraction of time that a chiller would run if it were to cycle because its load is smaller than the minimal load at which it can operature. Notice that this model does continuously operature even if the part load ratio is below the minimum part load ratio. Its leaving evaporator and condenser temperature can therefore be considered as an average temperature between the modes where the compressor is off and on. -
The test
PLR2 = max(PLRMinUnl, PLR1)
computes the part load ratio of the compressor. The assumption is that for a part load ratio belowPLRMinUnl, the chiller uses hot gas bypass to reduce the capacity, while the compressor power draw does not change.
The electric power only contains the power for the compressor, but not any power for pumps or fans.
Optionally, the model can be configured to represent heat recovery chillers with
a switchover option by setting the parameter have_switchover to
true.
In that case an additional Boolean input connector coo is used.
The chiller is tracking a chilled water supply temperature setpoint at the
outlet of the evaporator barrel if coo is true.
Otherwise, if coo is false, the chiller is tracking
a hot water supply temperature setpoint at the outlet of the condenser barrel.
See
Buildings.Fluid.Chillers.Examples.ElectricEIR_HeatRecovery
for an example with a chiller operating in heating mode.
Implementation
This implementation computes the chiller capacity and power consumption the same way as documented in EnergyPlus v22.1.0 Engineering Reference section 14.3.9.2. Especially see equations 14.234 and 14.240 in the referenced document.
The available chiller capacity QEva_flow_ava is adjusted from
its nominal capacity QEva_flow_nominal
by factor capFunT as
QEva_flow_ava = QEva_flow_nominal*capFunT
and the compressor power consumption is computed as
P = -QEva_flow_ava*(1/COP_nominal)*EIRFunT*EIRFunPLR*CR.
The models that extend from this base class implement the functions used above in ways that are shown in the table below.
| Function | Description | Formulation | |
|---|---|---|---|
ElectricEIR |
ElectricReformulatedEIR |
||
capFunT |
Adjusts cooling capacity for current fluid temperatures | Biquadratic on TConEnt and TEvaLvg |
Biquadratic on TConLvg and TEvaLvg |
EIRFunPLR |
Adjusts EIR for the current PLR | Quadratic on PLR | Bicubic on TConLvg and PLR |
EIRFunT |
Adjusts EIR for current fluid temperatures | Biquadratic on TConEnt and TEvaLvg |
Biquadratic on TConLvg and TEvaLvg |
where
TConEnt is the condenser entering temperature,
TEvaLvg is the evaporator leaving temperature,
TConLvg is the condenser leaving temperatore, and
PLR is the part load ratio.
References
Extends from Buildings.Fluid.Interfaces.FourPortHeatMassExchanger (Model transporting two fluid streams between four ports with storing mass or energy).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium1 | PartialMedium | Medium 1 in the component | |
| replaceable package Medium2 | PartialMedium | Medium 2 in the component | |
| Boolean | have_switchover | false | Set to true for heat recovery chiller with built-in switchover |
| Nominal condition | |||
| MassFlowRate | m1_flow_nominal | mCon_flow_nominal | Nominal mass flow rate [kg/s] |
| MassFlowRate | m2_flow_nominal | mEva_flow_nominal | Nominal mass flow rate [kg/s] |
| PressureDifference | dp1_nominal | Pressure difference [Pa] | |
| PressureDifference | dp2_nominal | Pressure difference [Pa] | |
| Assumptions | |||
| Boolean | allowFlowReversal1 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1 |
| Boolean | allowFlowReversal2 | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2 |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Medium 1 | |||
| Boolean | from_dp1 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance1 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM1 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Medium 2 | |||
| Boolean | from_dp2 | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance2 | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM2 | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics | |||
| Nominal condition | |||
| Time | tau1 | 30 | Time constant at nominal flow [s] |
| Time | tau2 | 30 | Time constant at nominal flow [s] |
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Initialization | |||
| Medium 1 | |||
| AbsolutePressure | p1_start | Medium1.p_default | Start value of pressure [Pa] |
| Temperature | T1_start | 273.15 + 25 | Start value of temperature [K] |
| MassFraction | X1_start[Medium1.nX] | Medium1.X_default | Start value of mass fractions m_i/m [kg/kg] |
| ExtraProperty | C1_start[Medium1.nC] | fill(0, Medium1.nC) | Start value of trace substances |
| ExtraProperty | C1_nominal[Medium1.nC] | fill(1E-2, Medium1.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
| Medium 2 | |||
| AbsolutePressure | p2_start | Medium2.p_default | Start value of pressure [Pa] |
| Temperature | T2_start | 273.15 + 5 | Start value of temperature [K] |
| MassFraction | X2_start[Medium2.nX] | Medium2.X_default | Start value of mass fractions m_i/m [kg/kg] |
| ExtraProperty | C2_start[Medium2.nC] | fill(0, Medium2.nC) | Start value of trace substances |
| ExtraProperty | C2_nominal[Medium2.nC] | fill(1E-2, Medium2.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| input BooleanInput | on | Set to true to enable compressor, or false to disable compressor |
| input RealInput | TSet | Set point for leaving chilled water temperature (condenser water if have_switchover=true and coo=false) [K] |
| output RealOutput | P | Electric power consumed by compressor [W] |
| output RealOutput | COP_h | Coefficient of performance of heating [1] |
| input BooleanInput | coo | Switchover signal: true for cooling, false for heating |
Modelica definition
partial model PartialElectric
"Partial model for electric chiller based on the model in DOE-2, CoolTools and EnergyPlus"
extends Buildings.Fluid.Interfaces.FourPortHeatMassExchanger(
m1_flow_nominal = mCon_flow_nominal,
m2_flow_nominal = mEva_flow_nominal,
T1_start = 273.15+25,
T2_start = 273.15+5,
redeclare final Buildings.Fluid.MixingVolumes.MixingVolume vol2(
V=m2_flow_nominal*tau2/rho2_nominal,
nPorts=2,
final prescribedHeatFlowRate=true),
vol1(
final prescribedHeatFlowRate=true));
parameter Boolean have_switchover=false
"Set to true for heat recovery chiller with built-in switchover";
Modelica.Blocks.Interfaces.BooleanInput on
"Set to true to enable compressor, or false to disable compressor";
Modelica.Blocks.Interfaces.RealInput TSet(unit="K", displayUnit="degC")
"Set point for leaving chilled water temperature (condenser water if have_switchover=true and coo=false)";
Modelica.Blocks.Interfaces.RealOutput P(final quantity="Power", unit="W")
"Electric power consumed by compressor";
Modelica.Blocks.Interfaces.RealOutput COP_h(final unit="1") if have_switchover
"Coefficient of performance of heating";
Modelica.Units.SI.Temperature TEvaEnt "Evaporator entering temperature";
Modelica.Units.SI.Temperature TEvaLvg "Evaporator leaving temperature";
Modelica.Units.SI.Temperature TConEnt "Condenser entering temperature";
Modelica.Units.SI.Temperature TConLvg "Condenser leaving temperature";
Modelica.Units.SI.Efficiency COP "Coefficient of performance";
Modelica.Units.SI.HeatFlowRate QCon_flow "Condenser heat input";
Modelica.Units.SI.HeatFlowRate QEva_flow "Evaporator heat input";
Real capFunT(min=0, unit="1")
"Cooling capacity factor function of temperature curve";
Modelica.Units.SI.Efficiency EIRFunT
"Power input to cooling capacity ratio function of temperature curve";
Modelica.Units.SI.Efficiency EIRFunPLR
"Power input to cooling capacity ratio function of part load ratio";
Real PLR1(min=0, unit="1", start=0) "Part load ratio";
Real PLR2(min=0, unit="1") "Part load ratio";
Real CR(min=0, unit="1") "Cycling ratio";
Controls.OBC.CDL.Interfaces.BooleanInput coo if have_switchover
"Switchover signal: true for cooling, false for heating";
Controls.OBC.CDL.Logical.Sources.Constant tru(
final k=true) if not have_switchover
"Constant true signal";
protected
Controls.OBC.CDL.Interfaces.BooleanInput coo_internal
"Internal switchover signal: true for cooling, false for heating";
Modelica.Units.SI.HeatFlowRate QEva_flow_ava(nominal=QEva_flow_nominal, start
=QEva_flow_nominal) "Cooling capacity available at evaporator";
Modelica.Units.SI.HeatFlowRate QEva_flow_set(nominal=QEva_flow_nominal, start
=QEva_flow_nominal)
"Cooling capacity required to cool to set point temperature";
Modelica.Units.SI.HeatFlowRate QCon_flow_set(
nominal=-QEva_flow_nominal * (1 + 1 / COP_nominal * etaMotor),
start=-QEva_flow_nominal * (1 + 1 / COP_nominal * etaMotor))
"Heating capacity required to heat up condenser water to setpoint";
Modelica.Units.SI.SpecificEnthalpy hSet
"Enthalpy setpoint for leaving chilled water";
// Performance data
parameter Modelica.Units.SI.HeatFlowRate QEva_flow_nominal(max=0)
"Reference capacity (negative number)";
parameter Modelica.Units.SI.Efficiency COP_nominal
"Reference coefficient of performance";
parameter Real PLRMax(min=0, unit="1") "Maximum part load ratio";
parameter Real PLRMinUnl(min=0, unit="1") "Minimum part unload ratio";
parameter Real PLRMin(min=0, unit="1") "Minimum part load ratio";
parameter Modelica.Units.SI.Efficiency etaMotor(max=1)
"Fraction of compressor motor heat entering refrigerant";
parameter Modelica.Units.SI.MassFlowRate mEva_flow_nominal
"Nominal mass flow at evaporator";
parameter Modelica.Units.SI.MassFlowRate mCon_flow_nominal
"Nominal mass flow at condenser";
parameter Modelica.Units.SI.Temperature TEvaLvg_nominal
"Temperature of fluid leaving evaporator at nominal condition";
final parameter Modelica.Units.NonSI.Temperature_degC TEvaLvg_nominal_degC=
Modelica.Units.Conversions.to_degC(TEvaLvg_nominal)
"Temperature of fluid leaving evaporator at nominal condition";
Modelica.Units.NonSI.Temperature_degC TEvaLvg_degC
"Temperature of fluid leaving evaporator";
parameter Modelica.Units.SI.HeatFlowRate Q_flow_small=QEva_flow_nominal*1E-9
"Small value for heat flow rate or power, used to avoid division by zero";
Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHeaFloEva
"Prescribed heat flow rate";
Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHeaFloCon
"Prescribed heat flow rate";
Modelica.Blocks.Sources.RealExpression QEva_flow_in(y=QEva_flow)
"Evaporator heat flow rate";
Modelica.Blocks.Sources.RealExpression QCon_flow_in(y=QCon_flow)
"Condenser heat flow rate";
Modelica.Blocks.Sources.RealExpression calCOPHea(
final y=QCon_flow/(P - Q_flow_small)) if have_switchover
"Compute heating COP";
initial equation
assert(QEva_flow_nominal < 0, "Parameter QEva_flow_nominal must be smaller than zero.");
assert(Q_flow_small < 0, "Parameter Q_flow_small must be smaller than zero.");
assert(PLRMinUnl >= PLRMin, "Parameter PLRMinUnl must be bigger or equal to PLRMin");
assert(PLRMax > PLRMinUnl, "Parameter PLRMax must be bigger than PLRMinUnl");
equation
// Condenser temperatures
TConEnt = Medium1.temperature(Medium1.setState_phX(port_a1.p,
inStream(port_a1.h_outflow),
inStream(port_a1.Xi_outflow)));
TConLvg = vol1.heatPort.T;
// Evaporator temperatures
TEvaEnt = Medium2.temperature(Medium2.setState_phX(port_a2.p, inStream(port_a2.h_outflow)));
TEvaLvg = vol2.heatPort.T;
TEvaLvg_degC=Modelica.Units.Conversions.to_degC(TEvaLvg);
// Enthalpy of temperature setpoint
hSet =if coo_internal then Medium2.specificEnthalpy_pTX(
p=port_b2.p,
T=TSet,
X=cat(
1,
port_b2.Xi_outflow,
{1 - sum(port_b2.Xi_outflow)})) else Medium1.specificEnthalpy_pTX(
p=port_b1.p,
T=TSet,
X=cat(
1,
port_b1.Xi_outflow,
{1 - sum(port_b1.Xi_outflow)}));
if on then
// Available cooling capacity
QEva_flow_ava = QEva_flow_nominal*capFunT;
// Cooling capacity required to chill water to setpoint
QEva_flow_set = Buildings.Utilities.Math.Functions.smoothMin(
x1=if coo_internal then m2_flow * (hSet - inStream(port_a2.h_outflow))
else P * etaMotor - QCon_flow_set,
x2=Q_flow_small,
deltaX=-Q_flow_small/100);
// Heating capacity required to heat up condenser water to setpoint
QCon_flow_set = if coo_internal then QCon_flow
else m1_flow * (hSet - inStream(port_a1.h_outflow));
// Part load ratio
PLR1 = Buildings.Utilities.Math.Functions.smoothMin(
x1 = QEva_flow_set/(QEva_flow_ava+Q_flow_small),
x2 = PLRMax,
deltaX=PLRMax/100);
// PLR2 is the compressor part load ratio. The lower bound PLRMinUnl is
// since for PLR1<PLRMinUnl, the chiller uses hot gas bypass, under which
// condition the compressor power is assumed to be the same as if the chiller
// were to operate at PLRMinUnl
PLR2 = Buildings.Utilities.Math.Functions.smoothMax(
x1 = PLRMinUnl,
x2 = PLR1,
deltaX = PLRMinUnl/100);
// Cycling ratio.
// Due to smoothing, this can be about deltaX/10 above 1.0
CR = Buildings.Utilities.Math.Functions.smoothMin(
x1 = PLR1/PLRMin,
x2 = 1,
deltaX=0.001);
// Compressor power.
P = -QEva_flow_ava/COP_nominal*EIRFunT*EIRFunPLR*CR;
// Heat flow rates into evaporator and condenser
// Q_flow_small is a negative number.
QEva_flow = Buildings.Utilities.Math.Functions.smoothMax(
x1 = QEva_flow_set,
x2 = QEva_flow_ava,
deltaX= -Q_flow_small/10);
//QEva_flow = max(QEva_flow_set, QEva_flow_ava);
QCon_flow = -QEva_flow + P*etaMotor;
// Coefficient of performance
COP = -QEva_flow/(P-Q_flow_small);
else
QEva_flow_ava = 0;
QEva_flow_set = 0;
QCon_flow_set = 0;
PLR1 = 0;
PLR2 = 0;
CR = 0;
P = 0;
QEva_flow = 0;
QCon_flow = 0;
COP = 0;
end if;
connect(calCOPHea.y, COP_h);
connect(QCon_flow_in.y, preHeaFloCon.Q_flow);
connect(preHeaFloCon.port, vol1.heatPort);
connect(QEva_flow_in.y, preHeaFloEva.Q_flow);
connect(preHeaFloEva.port, vol2.heatPort);
connect(coo, coo_internal);
connect(tru.y, coo_internal);
end PartialElectric;
Buildings.Fluid.Chillers.BaseClasses.warnIfPerformanceOutOfBounds
Function that checks the performance and writes a warning if it is outside of 0.9 to 1.1
Information
This function checks if the numeric argument is outside of the interval 0.9 to 1.1. If this is the case, the function writes a warning.
Inputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | x | Argument to be checked | |
| String | msg | String to be added to warning message | |
| String | curveName | Name of the curve that was tested |
Outputs
| Type | Name | Description |
|---|---|---|
| Integer | retVal | 0 if x is inside bounds, -1 if it is below bounds, or +1 if it is above bounds |
Modelica definition
impure function warnIfPerformanceOutOfBounds
"Function that checks the performance and writes a warning if it is outside of 0.9 to 1.1"
input Real x "Argument to be checked";
input String msg "String to be added to warning message";
input String curveName "Name of the curve that was tested";
output Integer retVal
"0 if x is inside bounds, -1 if it is below bounds, or +1 if it is above bounds";
algorithm
if (x > 1.1) then
retVal :=1;
elseif ( x < 0.9) then
retVal :=-1;
else
retVal :=0;
end if;
if (retVal <> 0) then
Modelica.Utilities.Streams.print(
"*** Warning: Chiller performance curves at nominal conditions are outside of bounds.
" + msg + " is outside of bounds 0.9 to 1.1.
The value of the curve fit is " + String(x) + "
Check the coefficients of the function " + curveName + ".");
end if;
end warnIfPerformanceOutOfBounds;