possible heat source

tom mcintyre

thanks for the answers, but they seem directed at friction heat and the compressed air is used for other purposes, painting, etc. and the heat is a secondary product not the process of compressing air for the sole purpose of heat. see why it's taken so long for an answer, this is the way it's been for years. thanks tom mcintyre

tom mcintyre

possible heat source

i've been asking about this for years without much luck, maybe someone there could provide an answer. compressed air in diesel engines creates a tremendous amount of heat in their cylinders 18:1 = 1200 degrees to ignite fuel, etc.
question 1 - how long can this compressed air retain its heat while being compressed? air conditioning works on just the opposite if not mistaken, after being compressed the expanding gases from being compressed turns cold. the
point of all this, question 2 - if compressed air could be compressed once and retain its heat or compressed over and over, again and again, as a compressor works can heat be taken from the result of this air compression process and
hopefully energy source ?
if you get a chance would appreciate a reply tom mcintyre

Tony Conner_2

The Usual...

... method is to run the exhaust gas stream through a heat recovery boiler - either steam or hot water. The diesel actually drives another piece of equipment like a compressor, pump, generator, etc. Some operations recover the heat out of the cooling jacket and lube oil coolers as well. I know of a diesel rigged to fire natural gas at an auto assembly plant near me that drives a big air compressor, and the exhaust is used to generate steam.

I don't know of any diesels driving refrigeration compressors, but there's no technical reason that they couldn't. Early air conditioning systems used compressed air, but they were really inefficient. (Air is a crappy refrigerant.) They quickly evolved into the principle used today - compress a refrigerant (ammonia, freon, etc), run it through a condenser to liquify it, then let it expand through a control valve or orifice. This is the evaporator, and the liquid boiling off pulls in heat, and cools the space. The refrigerant gas is sent back to the compressor, and the cycle starts again. It's like a steam system in reverse - almost all of the "action" stems from the change of state from a gas to a liquid, and back again. You can compress & liquify air, but the power required is huge, compared to something like ammonia.

Al Corelli

Most refrigerated trucks use a small diesel to run a compressoer (Thermo-King, Carrier, etc)