modelWetCoilEffectivenessNTUHeating

Model that validates the wet coil effectiveness-NTU model in heating conditions
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Extends from Modelica.Icons.Example (Icon for runnable examples).

Information

This model simulates various coil models in heating conditions, with

  • on the water-side: constant inlet temperature and mass flow rate,
  • on the air-side: constant inlet humidity ratio and mass flow rate, and an increasing inlet temperature.

To provide an accurate reference, the instance of Buildings.Fluid.HeatExchangers.DryCoilCounterFlow is configured with 30 elements. Under steady-state modeling assumptions, this creates a large system of non-linear equations. To alleviate this effect, dynamics are considered but the simulation time is increased to 1000 s to reproduce quasi steady-state conditions.

Parameters

TypeNameDefaultDescription
Modelica.Units.SI.AbsolutePressurepAtm101325Atmospheric pressure
Modelica.Units.SI.TemperatureT_a1_nominal50 + 273.15Inlet water temperature
Modelica.Units.SI.TemperatureT_b1_nominal45 + 273.15Outlet water temperature
Modelica.Units.SI.TemperatureT_a2_nominal273.15Inlet air temperature
Modelica.Units.SI.TemperatureT_b2_nominalT_a2_nominal + Q_flow_nominal/m2_flow_nominal/1010Outlet air temperature
Modelica.Units.SI.ThermalConductanceCMin_flow_nominalmin(m1_flow_nominal*4186, m2_flow_nominal*1010)Minimal capacity flow rate at nominal condition
Modelica.Units.SI.ThermalConductanceCMax_flow_nominalmax(m1_flow_nominal*4186, m2_flow_nominal*1010)Minimal capacity flow rate at nominal condition
Modelica.Units.SI.HeatFlowRateQ_flow_nominalm1_flow_nominal*4186*(T_a1_nominal - T_b1_nominal)
Realeps_nominalabs(Q_flow_nominal/((T_a1_nominal - T_a2_nominal)*CMin_flow_nominal))Nominal effectiveness
Modelica.Units.SI.ThermalConductanceUA_nominalBuildings.Fluid.HeatExchangers.BaseClasses.ntu_epsilonZ(eps = eps_nominal, Z = CMin_flow_nominal/CMax_flow_nominal, flowRegime = Integer(hexCon))*CMin_flow_nominalTotal thermal conductance at nominal flow
Modelica.Units.SI.MassFlowRatem1_flow_nominal3.78Nominal mass flow rate of water
Modelica.Units.SI.MassFlowRatem2_flow_nominal2.646Nominal mass flow rate of air
Types.HeatExchangerConfigurationhexConTypes.HeatExchangerConfiguration.CounterFlowHeat exchanger configuration

Components

TypeNameDefaultDescription
Buildings.Fluid.Sources.Boundary_pTsinAirAir sink
Sources.MassFlowSource_TsouAirAir source
Buildings.Fluid.Sources.Boundary_pTsinWatSink for water
Sensors.RelativeHumidityTwoPortrelHumInInlet relative humidity
Sensors.TemperatureTwoPortTDryBulInInlet dry bulb temperature
Sensors.MassFractionTwoPortsenMasFraInWater mass fraction of entering air
Sensors.MassFractionTwoPortsenMasFraOutWater mass fraction of leaving air
Sensors.TemperatureTwoPortTDryBulOutDry bulb temperature of leaving air
Sources.MassFlowSource_TsouWat1Source for water
DryCoilCounterFlowhexDisDiscretized coil model
Sources.MassFlowSource_TsouWatSource for water
Sources.MassFlowSource_TsouAir2Air source
Sensors.MassFractionTwoPortsenMasFraOut1Water mass fraction of leaving air
Sensors.TemperatureTwoPortTDryBulOut1Dry bulb temperature of leaving air
Sensors.RelativeHumidityTwoPortrelHumOut_epsOutlet relative humidity
Sensors.RelativeHumidityTwoPortrelHumOut_disOutlet relative humidity
Buildings.Fluid.HeatExchangers.DryCoilEffectivenessNTUhexDryNTU_TEffectiveness-NTU coil model (parameterized with nominal T and X)
Sources.MassFlowSource_TsouAir1Air source
Sources.MassFlowSource_TsouWat2Source for water
Controls.OBC.CDL.Reals.Sources.RampT_a2Air inlet temperature
Buildings.Fluid.HeatExchangers.WetCoilEffectivenessNTUhexWetNTU_TXEffectiveness-NTU coil model (parameterized with nominal T and X)

Contents

NameDescription
Medium_W
Medium_A

Revisions

  • Jan 21, 2021, by Antoine Gautier:
    First implementation.