modelWetCoilEffectivenessNTUCounterFlow

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

Information

This model is similar to Buildings.Fluid.HeatExchangers.Validation.WetCoilEffectivenessNTU, except that a discretized wet coil model is also simulated for comparison. To provide an accurate reference, the latter model 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_nominalModelica.Units.Conversions.from_degF(42)Inlet water temperature
Modelica.Units.SI.TemperatureT_a2_nominalModelica.Units.Conversions.from_degF(80)Inlet air temperature
Modelica.Units.SI.TemperatureT_b1_nominal273.15 + 11.0678Outlet water temperature in fully wet conditions
Modelica.Units.SI.TemperatureT_b2_nominal273.15 + 13.5805Outlet air temperature in fully wet conditions
Modelica.Units.SI.HeatFlowRateQ_flow_nominalm1_flow_nominal*4186*(T_a1_nominal - T_b1_nominal)
RealX_w_a2_nominal0.0173Inlet water mass fraction in fully wet conditions
Modelica.Units.SI.ThermalConductanceUA_nominal4748Total thermal conductance at nominal flow, from textbook
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
Buildings.Utilities.Psychrometrics.ToTotalAirconversion
Sensors.RelativeHumidityTwoPortrelHumInInlet relative humidity
Sensors.TemperatureTwoPortTDryBulInInlet dry bulb temperature
Modelica.Blocks.Sources.RealExpressionpAirAir pressure
Buildings.Utilities.Psychrometrics.TWetBul_TDryBulXiwetBulInComputation of wet bulb temperature
Sensors.MassFractionTwoPortsenMasFraInWater mass fraction of entering air
Sensors.MassFractionTwoPortsenMasFraOutWater mass fraction of leaving air
Sensors.TemperatureTwoPortTDryBulOutDry bulb temperature of leaving air
Buildings.Utilities.Psychrometrics.TWetBul_TDryBulXiwetBulOutComputation of wet bulb temperature
Modelica.Blocks.Sources.RealExpressionpAir1Air pressure
Buildings.Fluid.HeatExchangers.WetCoilEffectivenessNTUhexWetNTUEffectiveness-NTU coil model (parameterized with nominal UA)
Sources.MassFlowSource_TsouWat1Source for water
WetCoilCounterFlowhexDisDiscretized 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.WetCoilEffectivenessNTUhexWetNTU_TXEffectiveness-NTU coil model (parameterized with nominal T and X)
Sources.MassFlowSource_TsouAir1Air source
Sources.MassFlowSource_TsouWat2Source for water
Modelica.Blocks.Sources.CombiTimeTablew_a2Absolute humidity of entering air

Contents

NameDescription
Medium_W
Medium_A

Revisions

  • April 19, 2017, by Michael Wetter:
    Revised model to avoid mixing textual equations and connect statements.
  • March 17, 2017, by Michael O'Keefe:
    First implementation.