modelEvaporatorCondenserWithCapacity
Evaporaotr or condenser model with added capacity for heat losses to the ambient
Extends from Buildings.Fluid.Interfaces.TwoPortHeatMassExchanger (Partial model transporting one fluid stream with storing mass or energy).
Information
Model for an evaporator or condenser with the use of a capacity to simulate heat losses.
Used in Buildings.Fluid.HeatPumps.ModularReversible.Modular and Buildings.Fluid.Chillers.ModularReversible.Modular, the heat flow to or from the volume is calculated in a black-box. Thus the heat is directly added to the medium.
Transient heat losses are modelled by adding a capacity
and two convection components to
Buildings.Fluid.Interfaces.TwoPortHeatMassExchanger.
One of the convection component is between the capacity and the volume
(with thermal conductance GInn) and the other between
the capacity and the ambient heat port (with GOut).
Implementation
Both GInn and GOut are constants
but declared without a parameter keyword so that
the calculation can follow a temperature or flow-rate based approach.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | homotopyInitialization (from TwoPortHeatMassExchanger) | true | = true, use homotopy method |
| Boolean | isCon | =true for condenser, false for evaporator | |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal (from PartialTwoPortInterface) | Nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dp_nominal (from TwoPortFlowResistanceParameters) | Pressure difference | |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small (from PartialTwoPortInterface) | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortInterface) | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | computeFlowResistance (from TwoPortFlowResistanceParameters) | true | =true, compute flow resistance. Set to false to assume no friction |
| Boolean | from_dp (from TwoPortFlowResistanceParameters) | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Real | n (from TwoPortFlowResistanceParameters) | 2 | Flow exponent, n=1 for laminar, n=2 for turbulent |
| Boolean | linearizeFlowResistance (from TwoPortFlowResistanceParameters) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM (from TwoPortFlowResistanceParameters) | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics › Nominal condition | |||
| Modelica.Units.SI.Time | tau (from TwoPortHeatMassExchanger) | 30 | Time constant at nominal flow (if energyDynamics <> SteadyState) |
| Dynamics › Conservation equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics (from TwoPortHeatMassExchanger) | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
| Initialization | |||
| Medium.AbsolutePressure | p_start (from TwoPortHeatMassExchanger) | Medium.p_default | Start value of pressure |
| Medium.Temperature | T_start (from TwoPortHeatMassExchanger) | Medium.T_default | Start value of temperature |
| Medium.MassFraction[Medium.nX] | X_start (from TwoPortHeatMassExchanger) | Medium.X_default | Start value of mass fractions m_i/m |
| Medium.ExtraProperty[Medium.nC] | C_start (from TwoPortHeatMassExchanger) | fill(0, Medium.nC) | Start value of trace substances |
| Heat losses | |||
| Boolean | use_cap | true | False if capacity and heat losses are neglected |
| Modelica.Units.SI.HeatCapacity | C | Capacity of heat exchanger, set to zero to ignore its dry mass | |
| Initialization › Capacity | |||
| Modelica.Units.SI.Temperature | TCap_start | Medium.T_default | Initial temperature of heat capacity |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a (from PartialTwoPort) | Fluid connector a (positive design flow direction is from port_a to port_b) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b (from PartialTwoPort) | Fluid connector b (positive design flow direction is from port_a to port_b) | |
| Modelica.Blocks.Interfaces.RealOutput | GInn | Interior heat transfer coefficient | |
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | port_out | Temperature and heat flow to the ambient | |
| Modelica.Blocks.Interfaces.RealInput | Q_flow | Heat flow rate from the refrigerant to the medium | |
| Modelica.Blocks.Interfaces.RealOutput | T | Temperature of the condenser volume |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | m_flow (from PartialTwoPortInterface) | port_a.m_flow | Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp (from PartialTwoPortInterface) | port_a.p - port_b.p | Pressure difference between port_a and port_b |
| Medium.ThermodynamicState | sta_a (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow))) | Medium properties in port_a |
| Medium.ThermodynamicState | sta_b (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow)) | Medium properties in port_b |
| Buildings.Fluid.MixingVolumes.MixingVolume | vol (from TwoPortHeatMassExchanger) | ||
| Buildings.Fluid.FixedResistances.PressureDrop | preDro (from TwoPortHeatMassExchanger) | Flow resistance | |
| Modelica.Units.SI.ThermalConductance | GOut | Exterior heat transfer coefficient, set to zero to ignore external heat loss but keep the dry mass | |
| Modelica.Thermal.HeatTransfer.Components.Convection | conIns | Convection between the wall and the working fluid | |
| Modelica.Thermal.HeatTransfer.Components.Convection | conOut | Convection and conduction between the wall and ambient air | |
| Modelica.Thermal.HeatTransfer.Components.HeatCapacitor | heaCap | Heat Capacity | |
| Modelica.Blocks.Sources.RealExpression | heaLosInt | Nominal heat loss coefficient to the interior | |
| Modelica.Blocks.Sources.RealExpression | heaLosExt | Nominal heat loss coefficient to the exterior | |
| Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow | preHea | Heat flow rate of the condenser | |
| Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor | senT | Temperature sensor for the condenser volume |
Revisions
-
November 26, 2018, by Fabian Wuellhorst:
First implementation (see issue AixLib #577)