This is one of those programs that’s based on 1800’s math and 1960’s technology, but has been doggedly missing. It was driving me crazy.
It’s free and will run on MacOS, unix or even Windows with the right extra junk installed (a comment with the step-by-step details of installing said junk would be much appreciated).
Download it from http://crm.taoriver.net/simgas.tcl.
Download a non-fuzzy version of this movie from http://crm.taoriver.net/Simgas.mov.
This is super-duper-handy for solving PV=nRT, thermodynamics problems and modeling engine cycles.
It “thinks” in the metric system, but speaks whatever crazy units you like. P = giga bars? T = Rankine? V = mega cubic inches? W = horsepower-seconds? Sure. You can also define “mass” in moles.
It knows a bunch of gases: air, NH3 (ammonia), Ar (argon), C4H10 (butane), CO2 (carbon dioxide), CO (carbon monoxide), C2H6 (ethane), C2H4 (ethylene), He (helium), H2 (hydrogen), CH4 (methane), Ne (neon), N2 (nitrogen), C8H18 (octane), O2 (oxygen), C3H8 (propane), and H2O (steam).
You define which gas you want and then three of the four variables: P, V, mass and T. (You can also just say “STP” to do all three of them at once.) It solves for the fourth automatically (which is like a zillion freshman chemistry homework problems right there.)
In each step you can add to, subtract from, multiply or divide its pressure, volume or temperature adiabatically or at constant P, T or V. You can also add or take away heat or work.
After every step it tells you what the P, V, mass and T end up being, plus the Q and W involved in that step.
This program changed my life!
Longshot City 
September 9, 2009 at 4:50 pm
Hi! I was surfing and found your blog post… nice! I love your blog. 🙂 Cheers! Sandra. R.