Copyright Ian Bell, 2011 email: ian.h.bell@gmail.com
The function is called like
HAProps(‘H’,’T’,298.15,’P’,101.325,’R’,0.5)
which will return the enthalpy of the air for a set of inputs of dry bulb temperature of 25C, atmospheric pressure, and a relative humidity of 50%.
This function implements humid air properties based on the analysis in ASHRAE RP-1845 which is available online: http://rp.ashrae.biz/page/ASHRAE-D-RP-1485-20091216.pdf
It employs real gas properties for both air and water, as well as the most accurate interaction parameters and enhancement factors. The IAPWS-95 formulation for the properties of water is used throughout in preference to the industrial formulation. It is unclear why the industrial formulation is used in the first place.
Since humid air is nominally a binary mixture, three variables are needed to fix the state. At least one of the input parameters must be dry-bulb temperature, relative humidity, dew-point temperature, or humidity ratio. The others will be calculated. If the output variable is a transport property (conductivity or viscosity), the state must be able to be found directly - i.e. make sure you give temperature and relative humidity or humidity ratio. The list of possible input variables are
| String | Aliases | Description |
|---|---|---|
| T | Tdb | Dry-Bulb Temperature [K] |
| B | Twb | Wet-Bulb Temperature [K] |
| D | Tdp | Dew-Point Temperature [K] |
| P | Pressure [kPa] | |
| V | Vda | Mixture volume [m3/kg dry air] |
| R | RH | Relative humidity in (0,1) [-] |
| W | Omega | Humidity Ratio [kg water/kg dry air] |
| H | Hda | Mixture enthalpy [kJ/kg dry air] |
| S | Sda | Mixture entropy [kJ/kg dry air/K] |
| C | cp | Mixture specific heat [kJ/kg dry air/K] |
| M | Visc | Mixture viscosity [Pa-s] |
| K | Mixture thermal conductivity [kW/m/K] |
There are also strings for the mixture volume and mixture enthalpy that will return the properties on a total humid air flow rate basis, they are given by ‘Vha’ [units of m^3/kg humid air] and ‘Cha’ [units of kJ/kg humid air/K] and ‘Hha’ [units of kJ/kg humid air] respectively.
For more information, go to http://coolprop.sourceforge.net
Allows low-level access to some of the routines employed in HumidAirProps
Returns tuples of the form (Value, Units) where Value is the actual value and Units is a string that describes the units
The list of possible inputs is