Quote:
Originally Posted by GeeTwo
I don't believe that the air compressor would be well modeled as an isentropic (reversible) process. Even if the mechanical compression were isentropic, the presence of a heat sink at the compressor output radiating/convecting heat from the compressed air into the environment would make the process irreversible.
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Don't forget that any inefficiencies are going to be released as heat. That would include inefficiencies in the mechanics of the compressor as well as the motor inside of it. That being said, tanks aren't perfect insulators either, so some heat will escape through the walls (plastic is better than metal in that respect), so even if you model the compressor perfectly, you still have to model the whole system to get a decent model. For general FRC use, who really cares? Just use the manufactures' specs, but as an academic exercise, there are just far too many unknowns to take into account. There are things like back pressures that get involved with fittings, pressure loss in pneumatic lines, as well as heat loss in some of the larger metallic things like the pressure switch and any manifolds that are used. All that can add up. At any rate, I think isentropic is generally a good model for a compressor you don't know much about in terms of construction as long as you take efficiency into account. That being said, I do acknowledge that there probably is a math mistake in my spreadsheet somewhere because that temperature is extremely high (though the temperature does get extremely hot). We have melted high temp pressure tube coming off the compressor before switching to copper.