Buildings.Fluid.Chillers
Package with chiller models
Information
This package contains component models for chillers.
Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).
Package Content
Name  Description 

Carnot_TEva  Chiller with prescribed evaporator leaving temperature and performance curve adjusted based on Carnot efficiency 
Carnot_y  Chiller with performance curve adjusted based on Carnot efficiency 
ElectricEIR  Electric chiller based on the DOE2.1 model 
ElectricReformulatedEIR  Electric chiller based on the DOE2.1 model, but with performance as a function of condenser leaving instead of entering temperature 
Data  Performance data for electric chillers 
Examples  Collection of models that illustrate model use and test models 
Validation  Collection of models that validate the chiller models 
BaseClasses  Package with base classes for Buildings.Fluid.Chillers 
Buildings.Fluid.Chillers.Carnot_TEva
Chiller with prescribed evaporator leaving temperature and performance curve adjusted based on Carnot efficiency
Information
This is a model of a chiller 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 evaporator leaving temperature, which is met exactly at steady state if the chiller has sufficient capacity.
The model allows to either specify the Carnot effectivness η_{Carnot,0}, or a COP_{0} at the nominal conditions, together with the evaporator temperature T_{eva,0} and the condenser temperature T_{con,0}, in which case the model computes the Carnot effectivness as
η_{Carnot,0} = COP_{0} ⁄ (T_{eva,0} ⁄ (T_{con,0}T_{eva,0})).
On the Advanced
tab, a user can specify the temperatures that
will be used as the evaporator and condenser temperature.
During the simulation, the chiller COP is computed as the product
COP = η_{Carnot,0} COP_{Carnot} η_{PL},
where COP_{Carnot} is the Carnot efficiency and η_{PL} is a polynomial in the cooling part load ratio y_{PL} that can be used to take into account a change in COP at part load conditions. This polynomial has the form
η_{PL} = a_{1} + a_{2} y_{PL} + a_{3} y_{PL}^{2} + ...
where the coefficients a_{i}
are declared by the parameter a
.
On the Dynamics
tag, the model can be parametrized to compute a transient
or steadystate response.
The transient response of the model is computed using a first
order differential equation for the evaporator and condenser fluid volumes.
The chiller 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 added to the condenser. If the mass flow rate is too small, very high outlet temperatures can result.
The evaporator heat flow rate QEva_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 QEva_flow_nominal
is set to a reasonable value.
The maximum cooling capacity is set by the parameter QEva_flow_min
,
which is by default set to negative 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 heat pump, see Buildings.Fluid.HeatPumps.Examples.Carnot_TCon.
Extends from Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_T (Partial model for chiller with performance curve adjusted based on Carnot efficiency).
Parameters
Type  Name  Default  Description 

replaceable package Medium1  PartialMedium  Medium 1 in the component  
replaceable package Medium2  PartialMedium  Medium 2 in the component  
HeatFlowRate  QEva_flow_min  Modelica.Constants.inf  Maximum heat flow rate for cooling (negative) [W] 
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  QEva_flow_nominal*(1 + COP_...  Nominal heating flow rate [W] 
TemperatureDifference  dTEva_nominal  10  Temperature difference evaporator outletinlet [K] 
TemperatureDifference  dTCon_nominal  10  Temperature difference condenser outletinlet [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  COP_nominal/(TUseAct_nominal...  Carnot effectiveness (=COP/COP_Carnot) used if use_eta_Carnot_nominal = true [1] 
Real  COP_nominal  etaCarnot_nominal*TUseAct_no...  Coefficient of performance at TEva_nominal and TCon_nominal, used 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  1E4*abs(m1_flow_nominal)  Small mass flow rate for regularization of zero flow [kg/s] 
MassFlowRate  m2_flow_small  1E4*abs(m2_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  
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  TSet  Evaporator leaving water temperature [K] 
Modelica definition
Buildings.Fluid.Chillers.Carnot_y
Chiller with performance curve adjusted based on Carnot efficiency
Information
This is model of a chiller 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 η_{Carnot,0}, or a COP_{0} at the nominal conditions, together with the evaporator temperature T_{eva,0} and the condenser temperature T_{con,0}, in which case the model computes the Carnot effectivness as
η_{Carnot,0} = COP_{0} ⁄ (T_{eva,0} ⁄ (T_{con,0}T_{eva,0})).
The chiller COP is computed as the product
COP = η_{Carnot,0} COP_{Carnot} η_{PL},
where COP_{Carnot} is the Carnot efficiency and η_{PL} is a polynomial in the cooling part load ratio y_{PL} that can be used to take into account a change in COP at part load conditions. This polynomial has the form
η_{PL} = a_{1} + a_{2} y_{PL} + a_{3} y_{PL}^{2} + ...
where the coefficients a_{i}
are declared by the parameter a
.
On the Dynamics
tag, the model can be parametrized to compute a transient
or steadystate response.
The transient response of the model is computed using a first
order differential equation for the evaporator and condenser fluid volumes.
The chiller 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 evaporator heat flow rate QEva_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 QEva_flow_nominal
is set to a reasonable value.
The maximum cooling capacity is set by the parameter QEva_flow_min
,
which is by default set to negative 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 heat pump, see Buildings.Fluid.HeatPumps.Carnot_y.
Extends from Buildings.Fluid.Chillers.BaseClasses.PartialCarnot_y (Partial chiller model with performance curve adjusted based on Carnot efficiency).
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] 
TemperatureDifference  dTEva_nominal  10  Temperature difference evaporator outletinlet [K] 
TemperatureDifference  dTCon_nominal  10  Temperature difference condenser outletinlet [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  COP_nominal/(TUseAct_nominal...  Carnot effectiveness (=COP/COP_Carnot) used if use_eta_Carnot_nominal = true [1] 
Real  COP_nominal  etaCarnot_nominal*TUseAct_no...  Coefficient of performance at TEva_nominal and TCon_nominal, used 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  1E4*abs(m1_flow_nominal)  Small mass flow rate for regularization of zero flow [kg/s] 
MassFlowRate  m2_flow_small  1E4*abs(m2_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  
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
Buildings.Fluid.Chillers.ElectricEIR
Electric chiller based on the DOE2.1 model
Information
Model of an electric chiller, based on the DOE2.1 chiller model and
the EnergyPlus chiller model Chiller:Electric:EIR
.
This model uses three functions to predict capacity and power consumption:
 A biquadratic function is used to predict cooling capacity as a function of condenser entering and evaporator leaving fluid temperature.
 A quadratic functions is used to predict power input to cooling capacity ratio with respect to the part load ratio.
 A biquadratic functions is used to predict power input to cooling capacity ratio as a function of condenser entering and evaporator leaving fluid temperature.
These curves are stored in the data record per
and are available from
Buildings.Fluid.Chillers.Data.ElectricEIR.
Additional performance curves can be developed using
two available techniques (Hydeman and Gillespie, 2002). The first technique is called the
Leastsquares Linear Regression method and is used when sufficient performance data exist
to employ standard leastsquare linear regression techniques. The second technique is called
Reference Curve Method and is used when insufficient performance data exist to apply linear
regression techniques. A detailed description of both techniques can be found in
Hydeman and Gillespie (2002).
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 builtin, 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, per.PLRMax);
ensures that the chiller capacity does not exceed the chiller capacity specified by the parameterper.PLRMax
. 
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 operate. Note that this model continuously operates 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(per.PLRMinUnl, PLR1);
computes the part load ratio of the compressor. The assumption is that for a part load ratio belowper.PLRMinUnl
, 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.
The model can be parametrized to compute a transient or steadystate response. The transient response of the boiler is computed using a first order differential equation for the evaporator and condenser fluid volumes. The chiller outlet temperatures are equal to the temperatures of these lumped volumes.
References
 Hydeman, M. and K.L. Gillespie. 2002. Tools and Techniques to Calibrate Electric Chiller Component Models. ASHRAE Transactions, AC0291.
Extends from Buildings.Fluid.Chillers.BaseClasses.PartialElectric (Partial model for electric chiller based on the model in DOE2, CoolTools and EnergyPlus).
Parameters
Type  Name  Default  Description 

replaceable package Medium1  PartialMedium  Medium 1 in the component  
replaceable package Medium2  PartialMedium  Medium 2 in the component  
MixingVolumeHeatPort  vol1  vol1(final prescribedHeatFlo...  Volume for fluid 1 
Generic  per  Performance data  
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]  
Initialization  
Real  capFunT.start  1  Cooling capacity factor function of temperature curve [1] 
Efficiency  EIRFunT.start  1  Power input to cooling capacity ratio function of temperature curve [1] 
Efficiency  EIRFunPLR.start  1  Power input to cooling capacity ratio function of part load ratio [1] 
Real  PLR1.start  1  Part load ratio [1] 
Real  PLR2.start  1  Part load ratio [1] 
Real  CR.start  1  Cycling ratio [1] 
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  1E4*abs(m1_flow_nominal)  Small mass flow rate for regularization of zero flow [kg/s] 
MassFlowRate  m2_flow_small  1E4*abs(m2_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  
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] 
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 
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(1E2, 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(1E2, 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 [K] 
output RealOutput  P  Electric power consumed by compressor [W] 
Modelica definition
Buildings.Fluid.Chillers.ElectricReformulatedEIR
Electric chiller based on the DOE2.1 model, but with performance as a function of condenser leaving instead of entering temperature
Information
Model of an electric chiller, based on the model by
Hydeman et al. (2002) that has been developed in the CoolTools project
and that is implemented in EnergyPlus as the model
Chiller:Electric:ReformulatedEIR
.
This empirical model is similar to
Buildings.Fluid.Chillers.ElectricEIR.
The difference is that to compute the performance, this model
uses the condenser leaving temperature instead of the entering temperature,
and it uses a bicubic polynomial to compute the part load performance.
This model uses three functions to predict capacity and power consumption:
 A biquadratic function is used to predict cooling capacity as a function of condenser leaving and evaporator leaving fluid temperature.
 A bicubic function is used to predict power input to cooling capacity ratio as a function of condenser leaving temperature and part load ratio.
 A biquadratic functions is used to predict power input to cooling capacity ratio as a function of condenser leaving and evaporator leaving fluid temperature.
These curves are stored in the data record per
and are available from
Buildings.Fluid.Chillers.Data.ElectricReformulatedEIRChiller.
Additional performance curves can be developed using
two available techniques (Hydeman and Gillespie, 2002). The first technique is called the
Leastsquares Linear Regression method and is used when sufficient performance data exist
to employ standard leastsquare linear regression techniques. The second technique is called
Reference Curve Method and is used when insufficient performance data exist to apply linear
regression techniques. A detailed description of both techniques can be found in
Hydeman and Gillespie (2002).
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 builtin, 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, per.PLRMax);
ensures that the chiller capacity does not exceed the chiller capacity specified by the parameterper.PLRMax
. 
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 operate. Note that this model continuously operates 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(per.PLRMinUnl, PLR1);
computes the part load ratio of the compressor. The assumption is that for a part load ratio belowper.PLRMinUnl
, 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.
The model can be parametrized to compute a transient or steadystate response. The transient response of the boiler is computed using a first order differential equation for the evaporator and condenser fluid volumes. The chiller outlet temperatures are equal to the temperatures of these lumped volumes.
References
 Hydeman, M., N. Webb, P. Sreedharan, and S. Blanc. 2002. Development and Testing of a Reformulated RegressionBased Electric Chiller Model. ASHRAE Transactions, HI02182.
 Hydeman, M. and K.L. Gillespie. 2002. Tools and Techniques to Calibrate Electric Chiller Component Models. ASHRAE Transactions, AC0291.
Extends from Buildings.Fluid.Chillers.BaseClasses.PartialElectric (Partial model for electric chiller based on the model in DOE2, CoolTools and EnergyPlus).
Parameters
Type  Name  Default  Description 

replaceable package Medium1  PartialMedium  Medium 1 in the component  
replaceable package Medium2  PartialMedium  Medium 2 in the component  
MixingVolumeHeatPort  vol1  vol1(final prescribedHeatFlo...  Volume for fluid 1 
Generic  per  Performance data  
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]  
Initialization  
Real  capFunT.start  1  Cooling capacity factor function of temperature curve [1] 
Efficiency  EIRFunT.start  1  Power input to cooling capacity ratio function of temperature curve [1] 
Efficiency  EIRFunPLR.start  1  Power input to cooling capacity ratio function of part load ratio [1] 
Real  PLR1.start  1  Part load ratio [1] 
Real  PLR2.start  1  Part load ratio [1] 
Real  CR.start  1  Cycling ratio [1] 
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  1E4*abs(m1_flow_nominal)  Small mass flow rate for regularization of zero flow [kg/s] 
MassFlowRate  m2_flow_small  1E4*abs(m2_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  
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] 
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 
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(1E2, 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(1E2, 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 [K] 
output RealOutput  P  Electric power consumed by compressor [W] 