Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site h-sc1.UUCP Path: utzoo!decvax!genrad!mit-eddie!think!harvard!h-sc1!friedman From: friedman@h-sc1.UUCP (dawn friedman) Newsgroups: net.sf-lovers,net.physics Subject: Re: Discrepancies (Dune and Ringworld) Message-ID: <413@h-sc1.UUCP> Date: Sat, 29-Jun-85 18:02:11 EDT Article-I.D.: h-sc1.413 Posted: Sat Jun 29 18:02:11 1985 Date-Received: Sun, 30-Jun-85 06:14:55 EDT References: <2039@iddic.UUCP> <483@gitpyr.UUCP> <389@ttidcb.UUCP> <965@mhuxt.UUCP> Distribution: na Organization: Harvard Univ. Science Center Lines: 30 > Can some thermodynamics whiz in net.physics clear this up? The stillsuit > uses work provided by muscles to move heat from the interior of the suit (which > would have to be a little less than 37 celcius) to the exterior of the suit, > which could be around 45-65 celcius, I guess. The question is, could this > work, in principal? It seems as though it depends on the efficiency of > human muscles and the efficiency of the heat pump and the efficiency of the > external radiator. Obviously, if human muscles were 100% efficient (ie, > they change chemical to kinetic energy with no loss), then this could > work, regardless of the objections of the last person quoted above. Gah. I had hopes of staying out of this one, but can no longer retain my objectivity. What I want to do is separate the entropy question from the energy question, if this is possible. Is anyone still saying that you simply can't move heat from a colder object to a hotter object? This is the entropy part of it. You CAN, but it's not spontaneous: you have to put work into it. So it isn't going to work the way that was suggested earlier, that is, by evaporation balanced by condensation. (Unbalanced evaporation will cool you nicely and leave you a raisin; but if you evaporate the water within the stillsuit AND recondense it WITHIN the stillsuit, the stillsuit-bounded system remains at the same temperature; that was the point being made earlier.) So what was the cooling mechanism proposed in place of evaporation? After all, wasn't saving water the main point of the stillsuit? I'm quite willing to believe in a human-powered refrigerator suit; but I want to hear a proposal for a cooling mechanism. The two tablespoons of water or whatever minute quantity Kynes mentioned is not going to cool anything larger than a sandrat. dsf (Dina)