HumidAir Desktop Application

Psychrometrics desktop application based on a real gas formulation

For Windows 7 / Windows 8 / Windows 8.1 / Windows 10 / Windows 11

HumidAir Desktop Application

About Humid Air Application

The psychrometrics application calculates 35 thermodynamic properties of humid (moist) air in SI and English units.

It allows 21 different combinations of input variables to be used for calculations.

Input variables that can be used are:

  •  1 Pressure
  •  2 Dry bulb temperature
  •  3 Wet bulb temperature
  •  4 Dew bulb temperature
  •  5 Relative humidity
  •  6 Humidity ratio
  •  7 Enthalpy
  •  8 Entropy
  •  9 Volume

Main features of the application:
  • Professional quality, industrial strength software, proven in real world applications
  • Based on the real gas formulation developed by Hyland and Wexler
  • Developed in C++ for maximum speed
  • Copy and paste calculated results to Excel or other applications
  • One year free technical support

The following figure shows the HumidAir application.

HumidAir Desktop Application

HumidAir Desktop Application

Used Formulations

The psychrometrics application uses the most accurate formulations of thermodynamic properties of moist air.

Formulations are based on the study performed by Hyland and Wexler, and approved by ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers) as documented in the 1997 ASHRAE Handbook "Fundamentals". They presented the equation of state in:

  • Formulations for the thermodynamic properties of the saturated phases of H2O from 173.15 K to 473.15 K, W. Hyland and A.Wexler, ASHRAE Transactions, 89(2A) 500-519, 1983.
  • Formulations for the thermodynamic properties of dry air from 173.15 K to 473.15 K, and of saturated moist air from 173.15 K to 372.15 K, at pressures to 5 MPa, R. W. Hyland and A. Wexler, ASHRAE Transactions, 89(2A) 520-535, 1983.

Humid Air Application Functionality

The HumidAir is a standard win32 application. It is very ease to use, after selection of units (SI or English are supported) and completed calculation for entered parameters, results are displayed in the output table.

Obtained results can be saved to a file, printed, or copy and pasted (cell, row column or whole table) to Excel or any other application.

User privileges

Installation of the application requires standard privileges.

Humid (Moist) Air Properties

The following thermodynamic properties can be calculated with Humid Air Application:

Calculable properties in SI or E units - HumidAir Application v2.5
  1 Dry bulb temperature [Tdb]
  2 Wet bulb temperature [Twb]
  3 Dew point temperature [Tdp]
  4 Pressure [P]
  5 Saturation water pressure [Ps]
  6 Saturation pressure at wet bulb temperature [Pwb]
  7 Saturation pressure at dew point temperature [Pdp]
  8 Mole fraction of water [Xw]
  9 Mole fraction of air [Xa]
 10 Weight fraction of water [Ww]
 11 Weight fraction of air [Wa]
 12 Humidity ratio [W]
 13 Saturation humidity ratio [Ws]
 14 Degree of saturation [DS]
 15 Relative humidity [RH]
 16 Specific volume of dry air [Va]
 17 Specific volume of saturated ice [Vi]
 18 Specific volume of saturated water [Vw]
 19 Specific volume of saturated vapor [Vv]
 20 Specific volume of moist air [Vm]
 21 Specific density of dry air [Da]
 22 Specific density of saturated ice [Di]
 23 Specific density of saturated water [Dw]
 24 Specific density of saturated vapor [Dv]
 25 Specific density of moist air [Dm]
 26 Specific enthalpy of dry air [Ha]
 27 Specific enthalpy of saturated ice [Hi]
 28 Specific enthalpy of saturated water [Hw]
 29 Specific enthalpy of saturated vapor [Hv]
 30 Specific enthalpy of moist air [Hm]
 31 Specific entropy of dry air [Sa]
 32 Specific entropy of saturated ice [Si]
 33 Specific entropy of saturated water [Sw]
 34 Specific entropy of saturated vapor [Sv]
 35 Specific entropy of moist air [Sm]

Range of Validity

The entire set of equations used by the Humid Air application, is defined by the following temperature and pressure range:

  • 173.15 K <= T < = 473.15 K
  • 0.000001 MPa <= P < = 5 MPa

Moist Air Properties Limits

The upper limit of the absolute pressure is set at 5 MPa, and the temperature is restricted to the range -100 to 200°C. However, for any given absolute pressure, the highest temperature cannot exceed that temperature at which the saturation vapor pressure equals the absolute pressure.

In other words, moist air properties are valid for any dry-bulb temperatures below or equal to the saturation temperature of water at the same given absolute pressure, above that limit saturated moist air cannot exist.

Reference Point

In the used formulations for calculation of thermodynamic properties of moist air, the reference state (zero enthalpy) is set at 0 °C. On some psychrometric charts (especially in the US) the reference state (zero enthalpy) is set at 0 °F.

As a consequence, enthalpy and entropy values calculated by the library will be shifted on these charts for the difference between the reference points.

Since for any process calculation only enthalpy difference (in and out of a process) is important, the reference point doesn't really matter.

If you want to reproduce enthalpy values from such charts, you should find the enthalpy difference for one point (doesn't matter which one), and then add that value for all calculated enthalpies. The same applies for entropy values.


1. Humid Air Properties

HumidAir Application

Fig 1. HumidAir Application


Humid Air Desktop Application

- Download HumidAir Desktop Application version (2.5) - demo

You can also evaluate the HumidAir application online, visit "Psychromatric Calculator" web application. It uses the same calculation engine as the HumidAir desktop application.

Price info

Prices subject to change without notice!

HumidAir Application version 2.5
1-4 licensesUSD 149.95 per copy
5-20 licensesUSD 134.95 per copy
21 > licensesUSD 119.95 per copy
Company wide licenseUSD 3995.00


Each license also includes the following:

  • One year free e-mail technical support
  • One year free minor version updates if available (for example 2.6, 2.x up to, but not including version 3.0)

If you have any questions, please don't hesitate to contact sales. Contact information is provided on the following page:

 Contact Us - (opens in a new tab)

General Information

For quick access to the HumidAir Application, you may purchase and download our product using automated and secure online ordering system.
After ordering, you will receive a notification mail with further instructions for how to download and install the software.

The Registration includes a free subscription program. Each Registered user will be receiving bug fixes and technical support for the registered version within one year.

Shipping by the postal mail is not available.

How to order

1. Internet ordering

Available ordering options (open an order form to select):

  • Credit Card (Visa®, Mastercard®, American Express®, Discover®)
  • PayPal
  • Amazon

To buy a specific number of licenses for the HumidAir Application click the button: Open order page for the HumidAir Application.

To purchase a Company Wide License contact sales. Contact information is provided on the following page:
 Contact Us - (opens in a new tab)

2. Bank Direct Payment

If you prefer to pay for the product by "Bank Direct Payment", contact sales. Contact information is provided on the following page:

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