Software Resource & Applications

Psych: An Open Source Psychrometric Plug-in for Microsoft Excel by Kevin Brown


  • Minute-by-minute psychrometric calculations
  • Open Source/Public Domain
  • Find Wet Bulb depression, absolute humidity, Enthalpy (measure of internal energy), water vapor pressure, specific volume, moist air density


Psych is an Excel-Plugin or function that will calculate properties of moist air. Properties include wet bulb, dew point, RH, humidity ratio, vapor pressure, degree of saturation, enthalpy, specific volume of dry air, or moist air density based upon pressure, temperature, and one other parameter. This other parameter can be wet bulb, dew point, RH, humidity ratio or enthalpy.

Psych uses only equations from the ASHRAE 2005 Fundamentals Handbook, chapter 6. Please check the code for in-line documentation. Once installed, access the code by clicking on the “Developer Tab” then click “Visual Basic” in the “Code” group [for Excel 2007 and 2010].


Compatible with Microsoft Excel 2007 and 2012


Psych Plug-in Package

(Right Click and select “Save As”. 3MB Zip file. 4 documents: psych.xlam, ASHRAE2005Ch6_Fair Use.pdf, Psych as raw text.txt, PsychManual.pdf)

GitHub Version of Psych

Psychrometric Charts for CA Climate Zones 1-16 using Typical Meteorological Year Data

(Right Click and select “Save As”. 14.2MB xlsm file.)

Example screenshots from the Psych Excel Plug-in


R22 Calc: An Open Source LabView subVI to Calculate Saturation Temperature by Kevin Brown


The purpose of this LabView subVI is to calculate saturation temperature given absolute pressure of R-22. There are many equations availible for saturation pressure given temperature. This simply solves a simple one from DuPont for the Temperature using Newton-Ralphson method. Saturation temperature is needed to calculate superheat and subcooling. There is more documentation on the front panel.

R-22 is a pure substance, and is not a mixture. The saturation temperature is the same for boiling and condensing refrigerant


Requires LabView


R22 Calc subVI for Lab View

(Right Click and select “Save As”. 112KB Zip file. 1 document:

Thermodynamic Properties of DuPont Freon 22 Refrigerant

(Right Click and select “Save As”. 3.5MB PDF file.)