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Date:         Thu, 11 Aug 1994 16:27:58 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         cev@rocket.com (Charles E. Vaughan)
Subject:      Re: Solid State A/C

More later because this discussion is great. But just a note on Carnot efficiency. The formula is:

eff. = 1 - (T.cold/T.hot)

These are absolute temperatures so add 460 to deg. F or 273 to deg. C.

Example Car air temp desired 60 deg F = T.cold Heat rejected to outside air at 250 deg F = T.hot

eff. = 1 - ((60+460)/(250+460) = 0.27 or 27%

There is no firmly defined "theoretical limit" except it must be less than 1. The limits result from material capability and other practical limits (i.e. nobody wants -30 deg f air and accompanying ice in an A/C).

Gotta go for now.

Charles Vaughan '84 GL

>Interesting stuff about the Peltier devices and the Rovox Technology. > >It seems that the Rovox technology is still based on the Carnot cycle, and, if >my memory of those horrendous thermodynamics courses is accurate, the >theoretical limit of efficiency to the Carnot cycle is 25%, i.e., you have to >put in 4 units of energy for every unit of energy you suck out of the >chamber that is being cooled. In general, if I'm not mistaken, the >efficiency of air conditioners run around 12-15% (my data is probably old >and misunderstood -- please correct if so)... >


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