modelUACp
Calculates UA/Cp of the coil
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Information
This model calculates the UA/cp value and the bypass factor of the coil from the nominal inlet and outlet air properties.
For a heat exchanger where one medium changes phase, the NTU-ε relation is
ε = 1 - exp(-NTU) = 1-exp(-UA ⁄ cp ⁄ ṁ).
Since the bypass factor b is defined as b=1-ε, one can write
b = exp(-UA ⁄ cp ⁄ ṁ)
and, hence,
UA ⁄ cp = - ṁ log(b).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Buildings.Fluid.DXSystems.Cooling.AirSource.Data.Generic.BaseClasses.NominalValues | per | ||
| Modelica.Units.SI.MassFraction | XEvaIn_nominal | Buildings.Utilities.Psychrometrics.Functions.X_pSatpphi(pSat = Medium.saturationPressure(per.TEvaIn_nominal), p = per.p_nominal, phi = per.phiIn_nominal) | Rated/Nominal mass fraction of air entering coil |
| Modelica.Units.SI.SpecificEnthalpy | hEvaIn_nominal | Medium.specificEnthalpy_pTX(p = per.p_nominal, T = per.TEvaIn_nominal, X = cat(1, {XEvaIn_nominal}, {1 - sum({XEvaIn_nominal})})) | Rated enthalpy of air entering cooling coil |
| Modelica.Units.SI.SpecificEnthalpy | hOut_nominal | hEvaIn_nominal + per.Q_flow_nominal/per.m_flow_nominal | Rated enthalpy of air exiting cooling coil |
| Modelica.Units.SI.Temperature | TOut_nominal | per.TEvaIn_nominal + (per.SHR_nominal*per.Q_flow_nominal)/(per.m_flow_nominal*Cp_nominal) | Dry-bulb temperature of the air leaving the cooling coil at nominal condition |
| Modelica.Units.SI.MassFraction | XEvaOut_nominal | XEvaIn_nominal + (hOut_nominal - hEvaIn_nominal)*(1 - per.SHR_nominal)/Medium.enthalpyOfCondensingGas(T = per.TEvaIn_nominal) | Rated/Nominal mass fraction of air leaving the coil |
| Modelica.Units.SI.SpecificHeatCapacity | Cp_nominal | Medium.specificHeatCapacityCp(Medium.setState_pTX(p = per.p_nominal, T = per.TEvaIn_nominal, X = cat(1, {XEvaIn_nominal}, {1 - sum({XEvaIn_nominal})}))) | Specific heat of air at specified nominal condition |
| Modelica.Units.SI.MassFraction | XADP_nominal | Rated/Nominal mass fraction of air at coil apparatus dew point | |
| Modelica.Units.SI.Temperature | TADP_nominal | Coil apparatus dew point temperature | |
| Modelica.Units.SI.SpecificEnthalpy | hADP_nominal | Enthalpy of air at coil apparatus dew point (at rated condition) | |
| Real | bypass_nominal | Bypass factor for nominal condition | |
| Real | UAcp | UA/Cp of coil |
Contents
| Name | Description |
|---|---|
 Medium |
Revisions
-
November 11, 2020, by Michael Wetter:
Refactored to integrate directly a base class that was used only once in the library.
This is for #2229. -
April 14, 2020, by Michael Wetter:
ChangedhomotopyInitializationto a constant.
This is for IBPSA, #1341. -
September 21, 2012 by Michael Wetter:
Revised implementation and documentation. -
April 9, 2012 by Kaustubh Phalak:
First implementation.