Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/17/84; site mhuxt.UUCP
Path: utzoo!decvax!harpo!whuxlm!whuxl!houxm!ihnp4!mhuxn!mhuxr!mhuxt!js2j
From: js2j@mhuxt.UUCP (sonntag)
Newsgroups: net.sf-lovers,net.physics
Subject: Re: Discrepancies (Dune and Ringworld)
Message-ID: <965@mhuxt.UUCP>
Date: Tue, 25-Jun-85 16:37:47 EDT
Article-I.D.: mhuxt.965
Posted: Tue Jun 25 16:37:47 1985
Date-Received: Wed, 26-Jun-85 12:26:28 EDT
References: <2039@iddic.UUCP> <483@gitpyr.UUCP> <389@ttidcb.UUCP>
Distribution: na
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 39

> >>Stillsuits wouldn't work.  As I read it, the idea behind a stillsuit is
> >>that it allows cooling by evaporation while trapping the moisture. 
> >>Thermodynamics does not allow this.  Any cooling action gained by the
> >>evaporation inside the suit would be offset by the condensation process.
> >>
> >>The net result would be a steam box that would be hot on a cold day with
> >>any insolation at all.
> >
> >Sorry to disabuse you, but all Thermodynamics says is that you can't get
> >something for nothing.  If you recall, the description of the stillsuit
> >includes some form of "pump" which operates as the wearer walks.  This
> >provides the necessary "work" to circulate fluid.  A refrigerator works well
> >just by circulating fluid.  I haven't done any calculations, but on the
> >surface a stillsuit should be feasible.  Mike
> >-- 
> 
> I too, felt that stillsuits would not work, and having read _Dune_ a long
> time ago I don't remember what powered them. But, if the above description
> is accurate, then the stillsuits definately can't work. The "engines" for
> the "pump" are obviously human muscles which will generate heat.
> And because, as we all know "... 2) You can't break even ...", the wearer
> will produce more heat than they can remove; resulting in "friedman"
> (boiled might be more accurate).

     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.
-- 
Jeff Sonntag
ihnp4!mhuxt!js2j
   "Well I've been burned before, and I know the score,
    so you won't hear me complain.
    Are you willing to risk it all, or is your love in vain?"-Dylan