Buildings.Utilities.Psychrometrics.BaseClasses

Library with base classes for psychrometric classes

Information

Extends from Modelica.Fluid.Icons.BaseClassLibrary (Icon for library).

Package Content

NameDescription
Buildings.Utilities.Psychrometrics.BaseClasses.der_dewPointTemperature der_dewPointTemperature Derivative of dewPointTemperature function
Buildings.Utilities.Psychrometrics.BaseClasses.dewPointTemperature dewPointTemperature Function to compute the dew point temperature of moist air
Buildings.Utilities.Psychrometrics.BaseClasses.Examples Examples Collection of models that illustrate model use and test models
Buildings.Utilities.Psychrometrics.BaseClasses.HumidityRatioVaporPressure HumidityRatioVaporPressure Humidity ratio for given water vapor pressure


Buildings.Utilities.Psychrometrics.BaseClasses.der_dewPointTemperature

Derivative of dewPointTemperature function

Information


Derivative of dew point temperature calculation for moist air above freezing temperature.

Inputs

TypeNameDefaultDescription
TemperatureT Dew point temperature [K]
RealdT  

Outputs

TypeNameDescription
Realdp_wDifferential of water vapor partial pressure

Modelica definition

function der_dewPointTemperature 
  "Derivative of dewPointTemperature function"


  input Modelica.SIunits.Temperature T "Dew point temperature";
  input Real dT;
  output Real dp_w "Differential of water vapor partial pressure";
protected 
  constant Real C8 = -5.800226E3;
  constant Real C9 =  1.3914993E0;
  constant Real C10= -4.8640239E-2;
  constant Real C11 = 4.1764768E-5;
  constant Real C12= -1.4452093E-8;
  constant Real C13 = 6.5459673E0;
algorithm 
 dp_w := Modelica.Math.exp(C8/T + C9 + T * ( C10
           + T * ( C11 + T * C12))  + C13 * Modelica.Math.log(T))
           * (-C8/T/T+C10+2*C11*T+3*C12*T*T+C13/T)*dT;
end der_dewPointTemperature;

Buildings.Utilities.Psychrometrics.BaseClasses.dewPointTemperature

Function to compute the dew point temperature of moist air

Information


Dew point temperature calculation for moist air above freezing temperature.

The correlation used in this model is valid for dew point temperatures between 0 degC and 200 degC. It is the correlation from 2005 ASHRAE Handbook, p. 6.2. In an earlier version of this model, the equation from Peppers has been used, but this equation yielded about 15 Kelvin lower dew point temperatures.

Inputs

TypeNameDefaultDescription
TemperatureT Dew point temperature [K]

Outputs

TypeNameDescription
Pressurep_wWater vapor partial pressure [Pa]

Modelica definition

function dewPointTemperature 
  "Function to compute the dew point temperature of moist air"
  annotation(derivative=der_dewPointTemperature);


  input Modelica.SIunits.Temperature T "Dew point temperature";
  output Modelica.SIunits.Pressure p_w "Water vapor partial pressure";
protected 
  constant Real C8 = -5.800226E3;
  constant Real C9 =  1.3914993E0;
  constant Real C10= -4.8640239E-2;
  constant Real C11 = 4.1764768E-5;
  constant Real C12= -1.4452093E-8;
  constant Real C13 = 6.5459673E0;

algorithm 
 p_w := Modelica.Math.exp(C8/T + C9 + T * ( C10
           + T * ( C11 + T * C12))  + C13 * Modelica.Math.log(T));
end dewPointTemperature;

Buildings.Utilities.Psychrometrics.BaseClasses.HumidityRatioVaporPressure Buildings.Utilities.Psychrometrics.BaseClasses.HumidityRatioVaporPressure

Humidity ratio for given water vapor pressure

Buildings.Utilities.Psychrometrics.BaseClasses.HumidityRatioVaporPressure

Information


Partial Block to compute the relation between humidity ratio and water vapor partial pressure.

If use_p_in is false (default option), the p parameter is used as atmospheric pressure, and the p_in input connector is disabled; if use_p_in is true, then the p parameter is ignored, and the value provided by the input connector is used instead.

Extends from Modelica.Blocks.Interfaces.BlockIcon (Basic graphical layout of input/output block).

Parameters

TypeNameDefaultDescription
Booleanuse_p_intrueGet the pressure from the input connector
Pressurep101325Fixed value of pressure [Pa]

Connectors

TypeNameDescription
input RealInputp_inAtmospheric Pressure [Pa]

Modelica definition

partial block HumidityRatioVaporPressure 
  "Humidity ratio for given water vapor pressure"
  extends Modelica.Blocks.Interfaces.BlockIcon;
  parameter Boolean use_p_in = true "Get the pressure from the input connector";

  parameter Modelica.SIunits.Pressure p = 101325 "Fixed value of pressure";
  Modelica.Blocks.Interfaces.RealInput p_in(final quantity="Pressure",
                                         final unit="Pa",
                                         min = 0) if  use_p_in 
    "Atmospheric Pressure";

protected 
  Modelica.Blocks.Interfaces.RealInput p_in_internal 
    "Needed to connect to conditional connector";
equation 
  connect(p_in, p_in_internal);
  if not use_p_in then
    p_in_internal = p;
  end if;
end HumidityRatioVaporPressure;

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