PsychProps
PsychProps is a built-in procedure that provides a coding shortcut when determining two or more thermodynamic psychrometric properties, i.e., substance AIRH2O. This procedure will return temperature, specific volume, specific enthalpy, specific entropy, specific internal energy, humidity ratio, relative humidity, wetbulb, and dewpoint (in that order). The procedure requires three inputs, one of which must be atmospheric pressure The substance name (AIRH2O) is not required, but it can be provided. The list of property identifiers needed in the calling arguments and instructions are available in the Thermophysical Function help. The value and units of the inputs and outputs are determined by the Unit System setting.
Example:
$UnitSystem SI C kPa mass
T_1=25 [C]
P_1=100 [kPa]
RH_1=0.4
Call psychprops(T=T_1,P=P_1,R=RH_1:T_1, v_1,h_1,s_1,u_1,omega_1,RH_1,WetB_1,DewP_1)
{Solution
DewP_1=10.48 [C]
h_1=45.45 [kJ/kg]
omega_1=0.007986
P_1=100 [kPa]
RH_1=0.4
s_1=5.775 [kJ/kg-K]
T_1=25 [C]
u_1=-41.23 [kJ/kg]
v_1=0.8668 [m^3/kg]
WetB_1=16.16 [C]}
It is not necessary to have all of the output properties provided. If, one or more properties are not needed, just remove (or comment out) the variable name (but retain the commas) from the output list, or if they are at the end of the list, just don't include them. The following example evaluates just specific enthalpy and humidity ratio at the specified temperature and pressure.
$UnitSystem SI C kPa mass
T_1=25 [C]
P_1=100 [kPa]
RH_1=0.4
Call psychprops(T=T_1,P=P_1,R=RH_1: {T_1}, {v_1}, h_1, {s_1}, {u_1}, omega_1)
{Solution
h_1=45.45 [kJ/kg]
omega_1=0.007986
P_1=100 [kPa]
RH_1=0.4
T_1=25 [C]
}
See also: RealThermoProps