Package with base classes for Buildings.Fluid.Chillers
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).
Name | Description |
---|---|
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 |
Partial model for electric chiller based on the model in DOE-2, CoolTools and EnergyPlus
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:
PLR1 =min(QEva_flow_set/QEva_flow_ava, PLRMax);ensures that the chiller capacity does not exceed the chiller capacity specified by the parameter
PLRMax
.
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.
PLR2 = max(PLRMinUnl, PLR1);computes the part load ratio of the compressor. The assumption is that for a part load ratio below
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.
Models that extend from this base class need to provide three functions to predict capacity and power consumption:
capFunT
.
EIRFunT
.
EIRFunPLR
.
Extends from Buildings.Fluid.Interfaces.FourPortHeatMassExchanger (Model transporting two fluid streams between four ports with storing mass or energy).
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 | mCon_flow_nominal | Nominal mass flow rate [kg/s] |
MassFlowRate | m2_flow_nominal | mEva_flow_nominal | Nominal mass flow rate [kg/s] |
Pressure | dp1_nominal | Pressure [Pa] | |
Pressure | dp2_nominal | Pressure [Pa] | |
Initialization | |||
MassFlowRate | m1_flow.start | 0 | Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) [kg/s] |
Pressure | dp1.start | 0 | Pressure difference between port_a1 and port_b1 [Pa] |
MassFlowRate | m2_flow.start | 0 | Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) [kg/s] |
Pressure | dp2.start | 0 | Pressure difference between port_a2 and port_b2 [Pa] |
Assumptions | |||
Boolean | allowFlowReversal1 | system.allowFlowReversal | = true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b) |
Boolean | allowFlowReversal2 | system.allowFlowReversal | = true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b) |
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] |
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... | Formulation of energy balance |
Dynamics | massDynamics | energyDynamics | Formulation of mass balance |
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.) |
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] |
Function that checks the performance and writes a warning if it is outside of 0.9 to 1.1
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.
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 |
Type | Name | Description |
---|---|---|
Integer | retVal | 0 if x is inside bounds, -1 if it is below bounds, or +1 if it is above bounds |