Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics

Package with obsolete models for psychrometric calculations

Information

Package that contains obsolete models for psychrometric calculations.

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name	Description
TDewPoi_TDryBulPhi	Block to compute the dew point temperature based on relative humidity
TWetBul_TDryBulPhi	Block to compute the wet bulb temperature based on relative humidity
h_TDryBulPhi	Block to compute the specific enthalpy based on relative humidity
Validation	Collection of validation models

Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.TDewPoi_TDryBulPhi

Block to compute the dew point temperature based on relative humidity

Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.TDewPoi_TDryBulPhi

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°C and 93°C. It is the correlation from 2009 ASHRAE Handbook Fundamentals, p. 1.9, equation 39.

Extends from Modelica.Icons.ObsoleteModel (Icon for classes that are obsolete and will be removed in later versions).

Connectors

Type	Name	Description
input RealInput	TDryBul	Dry bulb temperature [K]
input RealInput	phi	Relative air humidity [1]
input RealInput	p	Pressure [Pa]
output RealOutput	TDewPoi	Dew point temperature [K]

Modelica definition

block TDewPoi_TDryBulPhi "Block to compute the dew point temperature based on relative humidity" extends Modelica.Icons.ObsoleteModel; Buildings.Controls.OBC.CDL.Interfaces.RealInput TDryBul( final quantity="ThermodynamicTemperature", final unit="K", final min=100) "Dry bulb temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput phi(final min=0, final max=1, unit="1") "Relative air humidity"; Buildings.Controls.OBC.CDL.Interfaces.RealInput p(final quantity="Pressure", final unit="Pa", final min = 0) "Pressure"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput TDewPoi( final quantity="ThermodynamicTemperature", final unit="K", final min=100) "Dew point temperature"; protected Modelica.SIunits.Pressure p_w(displayUnit="Pa") "Water vapor pressure"; constant Real C14=6.54 "Constant used in the equation"; constant Real C15=14.526 "Constant used in the equation"; constant Real C16=0.7389 "Constant used in the equation"; constant Real C17=0.09486 "Constant used in the equation"; constant Real C18=0.4569 "Constant used in the equation"; Real alpha "Variable used in the equation"; equation p_w = phi * Buildings.Utilities.Psychrometrics.Functions.saturationPressure(TDryBul); alpha = Modelica.Math.log(p_w/1000.0); TDewPoi = (C14 + C15*alpha + C16*alpha^2 + C17*alpha^3 + C18*(p_w/1000.0)^0.1984)+273.15; end TDewPoi_TDryBulPhi;

Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.TWetBul_TDryBulPhi

Block to compute the wet bulb temperature based on relative humidity

Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.TWetBul_TDryBulPhi

Information

This block computes the wet bulb temperature for a given dry bulb temperature, relative air humidity and atmospheric pressure.

The block uses the approximation of Stull (2011) to compute the wet bulb temperature without requiring a nonlinear equation. The approximation by Stull is valid for a relative humidity of 5% to 99%, a temperature range from -20°C to 50°C and standard sea level pressure. For this range of data, the approximation error is -1 Kelvin to +0.65 Kelvin, with a mean error of less than 0.3 Kelvin.

The model is validated in Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.Validation.TWetBul_TDryBulPhi.

For a model that takes the mass fraction instead of the relative humidity as an input, see Buildings.Utilities.Psychrometrics.TWetBul_TDryBulXi.

References

Stull, Roland. Wet-Bulb Temperature from Relative Humidity and Air Temperature Roland Stull. Journal of Applied Meteorology and Climatology. Volume 50, Issue 11, pp. 2267-2269. November 2011 DOI: 10.1175/JAMC-D-11-0143.1

Extends from Modelica.Icons.ObsoleteModel (Icon for classes that are obsolete and will be removed in later versions).

Connectors

Type	Name	Description
input RealInput	TDryBul	Dry bulb temperature [K]
input RealInput	phi	Relative air humidity
input RealInput	p	Pressure [Pa]
output RealOutput	TWetBul	Wet bulb temperature [K]

Modelica definition

block TWetBul_TDryBulPhi "Block to compute the wet bulb temperature based on relative humidity" extends Modelica.Icons.ObsoleteModel; Buildings.Controls.OBC.CDL.Interfaces.RealInput TDryBul( final quantity="ThermodynamicTemperature", final unit="K", final min=100) "Dry bulb temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput phi( final min=0, final max=1) "Relative air humidity"; Buildings.Controls.OBC.CDL.Interfaces.RealInput p( final quantity="Pressure", final unit="Pa", final min = 0) "Pressure"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput TWetBul( final quantity="ThermodynamicTemperature", final unit="K", final min=100) "Wet bulb temperature"; protected Modelica.SIunits.Conversions.NonSIunits.Temperature_degC TDryBul_degC "Dry bulb temperature in degree Celsius"; Real rh_per(min=0) "Relative humidity in percentage"; equation TDryBul_degC = TDryBul - 273.15; rh_per = 100*phi; TWetBul = 273.15 + TDryBul_degC * Modelica.Math.atan(0.151977 * sqrt(rh_per + 8.313659)) + Modelica.Math.atan(TDryBul_degC + rh_per) - Modelica.Math.atan(rh_per-1.676331) + 0.00391838 * rh_per^(1.5) * Modelica.Math.atan( 0.023101 * rh_per) - 4.686035; end TWetBul_TDryBulPhi;

Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.h_TDryBulPhi

Block to compute the specific enthalpy based on relative humidity

Buildings.Obsolete.Controls.OBC.CDL.Psychrometrics.h_TDryBulPhi

Information

The correlation used in this model is from 2009 ASHRAE Handbook Fundamentals, p. 1.9, equation 32.

Extends from Modelica.Icons.ObsoleteModel (Icon for classes that are obsolete and will be removed in later versions).

Connectors

Type	Name	Description
input RealInput	TDryBul	Dry bulb temperature [K]
input RealInput	phi	Relative air humidity
input RealInput	p	Pressure [Pa]
output RealOutput	h	Specific enthalpy [J/kg]

Modelica definition

block h_TDryBulPhi "Block to compute the specific enthalpy based on relative humidity" extends Modelica.Icons.ObsoleteModel; Buildings.Controls.OBC.CDL.Interfaces.RealInput TDryBul( final quantity="ThermodynamicTemperature", final unit="K", final min=100) "Dry bulb temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput phi(final min=0, final max=1) "Relative air humidity"; Buildings.Controls.OBC.CDL.Interfaces.RealInput p( final quantity="Pressure", final unit="Pa", final min = 0) "Pressure"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput h( final quantity="SpecificEnergy", final unit="J/kg") "Specific enthalpy"; protected Modelica.SIunits.Conversions.NonSIunits.Temperature_degC TDryBul_degC "Dry bulb temperature in degree Celsius"; Modelica.SIunits.Pressure p_w(displayUnit="Pa") "Water vapor pressure"; Real w(final unit="1", nominal=0.01) "Water vapor mass fraction in kg per kg dry air"; // Modelica.SIunits.Temperature T_ref = 273.15 // "Reference temperature for psychrometric calculations" // constant Modelica.SIunits.SpecificHeatCapacity cpAir=1006 // "Specific heat capacity of air"; // constant Modelica.SIunits.SpecificHeatCapacity cpSte=1860 // "Specific heat capacity of water vapor"; // constant Modelica.SIunits.SpecificHeatCapacity cpWatLiq = 4184 // "Specific heat capacity of liquid water"; // constant Modelica.SIunits.SpecificEnthalpy h_fg = 2501014.5 // "Enthalpy of evaporation of water at the reference temperature"; // constant Real k_mair = 0.6219647130774989 "Ratio of molar weights"; equation TDryBul_degC = TDryBul - 273.15; p_w = phi * Buildings.Utilities.Psychrometrics.Functions.saturationPressure(TDryBul); w = 0.6219647130774989*p_w/(p-p_w); h = 1006*TDryBul_degC + w*(2501014.5+1860*TDryBul_degC); end h_TDryBulPhi;