technical information

MoistAirTab™ Technical Information

Design

MoistAirTab uses an equation of state to compute all of the thermodynamic properties. MoistAirTab uses formulations that are approved by the American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. (ASHRAE) as documented in the 1997 ASHRAE Handbook: Fundamentals. The equation-of-state used to compute the moist air properties are given in:

MoistAirTab Functions

The MoistAirTab add-in package is based on a set of 18 core functions that together calculate over 25 thermodynamic and transport properties of steam. You can use these functions directly in your spreadsheet or you can use MoistAirTab’s easy-to-use dialog boxes to automatically generate the appropriate function call with the correct arguments.

All of the MoistAirTab functions begin with the prefix MA. The MoistAirTab functions require as input two independent variables in addition to the total pressure. The first independent variable can be either: Dry bulb temperature (Tdb), Humidity Ratio (W), or Relative Humidity (RH). The second independent variable can be either: Dry-bulb Temperature (Tdb), Wet-bulb Temperature (Twb), Humidity Ratio (W), or Relative Humidity (RH), Enthalpy (H), Entropy (S), or Volume (V). These functions are summarized in Table 1 below.

MoistAirTab also includes functions for obtaining the barometric pressure and temperature as a function of altitude.

Table 1: MoistAirTab Worksheet Functions

The MoistAirTab functions return the requested property in either Metric/SI or English units. The thermodynamic properties and the units in which they are available is shown in the following table. Properties highlighted in red are MoistAirTab V2 additions.

Table 2: MoistAirTab V2 Thermodynamic and Transport Properties