modelWetCoilEffectivenessNTU

Model that validates the wet coil effectiveness-NTU model

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 Buildings.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

Type	Name	Default	Description
Modelica.Units.SI.AbsolutePressure	pAtm	101325	Atmospheric pressure
Modelica.Units.SI.Temperature	T_a1_nominal	Modelica.Units.Conversions.from_degF(42)	Inlet water temperature
Modelica.Units.SI.Temperature	T_a2_nominal	Modelica.Units.Conversions.from_degF(80)	Inlet air temperature
Modelica.Units.SI.Temperature	T_b1_nominal	273.15 + 11.0678	Outlet water temperature in fully wet conditions
Modelica.Units.SI.Temperature	T_b2_nominal	273.15 + 13.5805	Outlet air temperature in fully wet conditions
Modelica.Units.SI.HeatFlowRate	Q_flow_nominal	m1_flow_nominal4186(T_a1_nominal - T_b1_nominal)
Real	X_w_a2_nominal	0.0173	Inlet water mass fraction in fully wet conditions
Modelica.Units.SI.ThermalConductance	UA_nominal	4748	Total thermal conductance at nominal flow, from textbook
Modelica.Units.SI.MassFlowRate	m1_flow_nominal	3.78	Nominal mass flow rate of water
Modelica.Units.SI.MassFlowRate	m2_flow_nominal	2.646	Nominal mass flow rate of air
Types.HeatExchangerConfiguration	hexCon	Types.HeatExchangerConfiguration.CounterFlow	Heat exchanger configuration

Components

Type	Name	Description
Buildings.Fluid.Sources.Boundary_pT	sinAir	Air sink
Sources.MassFlowSource_T	souAir	Air source
Buildings.Fluid.Sources.Boundary_pT	sinWat	Sink for water
Buildings.Utilities.Psychrometrics.ToTotalAir	conversion
Sensors.RelativeHumidityTwoPort	relHumIn	Inlet relative humidity
Sensors.TemperatureTwoPort	TDryBulIn	Inlet dry bulb temperature
Modelica.Blocks.Sources.RealExpression	pAir	Air pressure
Buildings.Utilities.Psychrometrics.TWetBul_TDryBulXi	wetBulIn	Computation of wet bulb temperature
Sensors.MassFractionTwoPort	senMasFraIn	Water mass fraction of entering air
Sensors.MassFractionTwoPort	senMasFraOut	Water mass fraction of leaving air
Sensors.TemperatureTwoPort	TDryBulOut	Dry bulb temperature of leaving air
Buildings.Utilities.Psychrometrics.TWetBul_TDryBulXi	wetBulOut	Computation of wet bulb temperature
Modelica.Blocks.Sources.RealExpression	pAir1	Air pressure
Buildings.Fluid.HeatExchangers.WetCoilEffectivenessNTU	hexWetNTU	Effectiveness-NTU coil model (parameterized with nominal UA)
Sources.MassFlowSource_T	souWat1	Source for water
Sensors.RelativeHumidityTwoPort	relHumOut_eps	Outlet relative humidity
Buildings.Fluid.HeatExchangers.WetCoilEffectivenessNTU	hexWetNTU_TX	Effectiveness-NTU coil model (parameterized with nominal T and X)
Sources.MassFlowSource_T	souAir1	Air source
Sources.MassFlowSource_T	souWat2	Source for water
Modelica.Blocks.Sources.CombiTimeTable	w_a2	Absolute humidity of entering air

Name	Description
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.