From: schinder@leprss.gsfc.nasa.gov (Paul J. Schinder)
Newsgroups: talk.origins
Subject: Re: Thermodynamics FAQ
Date: 31 Jul 92 19:34:11 GMT
Reply-To: schinder@leprss.gsfc.nasa.gov
Organization: Goddard Space Flight Center

In <henley.920731131534@wilbur.eng.auburn.edu> henley@eng.auburn.edu (James Paul Henley) writes:

>In article <schinder.712601661@leprss.gsfc.nasa.gov> schinder@leprss.gsfc.nasa.gov writes:
>>
>>Uhh, I thought plants produced O2 from C02, more than they use in
>>respiration (that's why the atmosphere of the earth is polluted with
>>O2 and out of equilibrium).  *Eventually* the plant will eat up the
>>carbon supply, and I suppose it'll die then.  So?

>The point is, that without a cyclical heat supply, you can't drive the cyclical
>processes necessary.

I'm curious about this need you have for cyclical processes.  Many
processes are, many aren't.  Would you call a photocell "cyclical"
(maybe if you look at the microphysics, but you don't seem to like
that)?  I don't know exactly what you mean by cyclical in this regard.

>>
>>How do you suppose the space shuttle gets rid of its excess heat?  Do
>>you know *why* they open the cargo bay doors as soon as possible?

>I thought the sun only shone on one side of the shuttle.  The other side
>has a heat sink.  Just like the earth.  Unlike my proposed system.

The shuttle (I'm not involved in the shuttle program, so all this is
from memory of various popular articles I read over the years) is well
insulated, and, as I recall, can last only about 6 hours or so before
thermal buildup makes things uncomfortable for the crew.  The insides
of the cargo doors contain thermal radiators, and I believe they run a
working fluid through the shuttle and into the radiators so that they
can vent radiation (there's obviously no conduction or convection to
speak of) to space.  I find it somewhat interesting that you'd
consider this a "heat sink" (pointing out that differences in types of
energy are superficial is my schtick :-)), since you seemed to claim
special status for heat in a previous article.  The shuttle cools
itself by radiation alone.

>>
>>Yes, but you can run an engine so long as there's an energy supply.

>Not a PMM2 you can't.  People tried for years and years, but they finally
>decided that it was impossible.  A PMM2 *DOES* have a heat source, it
>just doesn't have a heat sink.

>That's why my proposed system will fry - no heat sink.  By the second law
>of thermodynamics you cannot convert heat into work without a heat sink.
>It is impossible for a plant to continuously convert sunlight into
>chemical energy without a heat sink.
>As you said - no differential.  It takes a differential to get an energy
>flow.  In my system there is no external differential - it is uniform.

Yeah, I agree with this, and thanks for clarifying.  In short, if you
put something into an oven, it'll heat up (eventually) to the
temperature of the oven, and there's nothing you can do about it.
But, getting back to the point of this group, the earth and the life
on it isn't stuck in this situation.  There's always the 3K universe
to dump to.

>James P. Henley Jr.
>Chemical Engineering Dept
>Auburn University
--
--------
Paul J. Schinder
NASA Goddard Space Flight Center
schinder@leprss.gsfc.nasa.gov
Newsgroups: talk.origins