modelWetCoilEffectivenessNTU

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 duplicates an example from Mitchell and Braun 2012, example SM-2-1 (Mitchell and Braun 2012) to validate a single case for the BuildingSystems.Fluid.HeatExchangers.WetCoilEffectivenessNTU model.

Validation

The example simulates a wet coil with constant air and water inlet temperature and mass flow rate, and an increasing air inlet humidity which triggers the transition from a fully-dry to a fully-wet regime. The reference used for validation is the published experimental data.

Note that the outlet air relative humidity may slightly exceed 100% when using the epsilon-NTU model.

References

Mitchell, John W., and James E. Braun. 2012. "Supplementary Material Chapter 2: Heat Exchangers for Cooling Applications". Excerpt from Principles of heating, ventilation, and air conditioning in buildings. Hoboken, N.J.: Wiley. Available online: http://bcs.wiley.com/he-bcs/Books?action=index&itemId=0470624574&bcsId=7185

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
BuildingSystems.Fluid.Sources.Boundary_pTsinAirAir sink
Sources.MassFlowSource_TsouAirAir source
BuildingSystems.Fluid.Sources.Boundary_pTsinWatSink for water
BuildingSystems.Utilities.Psychrometrics.ToTotalAirconversion
Sensors.RelativeHumidityTwoPortrelHumInInlet relative humidity
Sensors.TemperatureTwoPortTDryBulInInlet dry bulb temperature
Modelica.Blocks.Sources.RealExpressionpAirAir pressure
BuildingSystems.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
BuildingSystems.Utilities.Psychrometrics.TWetBul_TDryBulXiwetBulOutComputation of wet bulb temperature
Modelica.Blocks.Sources.RealExpressionpAir1Air pressure
BuildingSystems.Fluid.HeatExchangers.WetCoilEffectivenessNTUhexWetNTUEffectiveness-NTU coil model (parameterized with nominal UA)
Sources.MassFlowSource_TsouWat1Source for water
Sensors.RelativeHumidityTwoPortrelHumOut_epsOutlet relative humidity
BuildingSystems.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.