A Java Applet for Computing the Thermodynamic Properties of Air Under Equilibrium Conditions

This applet calculates the thermodynamic properties of air given the pressure and entropy, pressure and density, specific energy and density, entropy and enthalpy, or pressure and temperature, in SI units (kg/m^3, J/kg, J/kg/K, m/s, Pa, K) or British Units (lb/ft^3, BTU/lbm, BTU/lbm/R, ft/s, psi, R).

Instructions

• 1. To launch the calculator press the button above. After a few seconds (to download the bytecode) the calculator will start in a separate window. This window will remain active until you close it, or exit your browser - it is not necessary to be looking at this page to use the calculator). Note that by pressing the button more than once you can simultaneously launch multiple copies of the applet. Also note that you may resize the calculator window to suit your screen.
• 2. Select (using the choice fields at the bottom left) the type of input you wish to give and the units in which you want to give it.
• 3. Clear the text areas using the 'Clear' button, and then type/paste into the top text area a list of point pairs e.g.
```100000 1.0
100000 1.1
100000 1.2
etc...
```
which would be a suitable input for "pressure,density" with "SI Units". Note that the applet is designed especially to allow you to cut and paste in lists of point pairs from other applications such as Excel and, indeed, it is a lot easier to do it this way.
• 4. Press the compute button and the full thermodynamic properties corresponding to each pair of properties is tabulated and displayed in the lower window using the units you selected. You may then cut and paste this table back into, for example, Excel to plot the results (if that's what you want to do). Note that if the returned values are marked with a '?' this indicates that the computation went beyond the valid range of the tables, and your answers may be inaccurate (or just plain wrong).
This applet should now be fully debugged. The source code for the GUI part of the applet is found at tgas.java and eqair.java, the computational subroutines are found in the class file gasState.java which may be compared with the fortran version of the code tgas.f.

Please let me know if you have any questions, or find a bug that I missed, at William Devenport