Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site rtp47.UUCP Path: utzoo!decvax!mcnc!rti-sel!rtp47!throopw From: throopw@rtp47.UUCP (Wayne Throop) Newsgroups: net.sf-lovers,net.physics Subject: Re: Discrepancies (Dune and Ringworld) Message-ID: <82@rtp47.UUCP> Date: Mon, 1-Jul-85 11:40:36 EDT Article-I.D.: rtp47.82 Posted: Mon Jul 1 11:40:36 1985 Date-Received: Wed, 3-Jul-85 01:33:52 EDT References: <2039@iddic.UUCP> <483@gitpyr.UUCP> <389@ttidcb.UUCP> <965@mhuxt.UUCP> <413@h-sc1.UUCP> Distribution: na Organization: Data General, RTP, NC Lines: 50 Xref: pepe net.sf-lovers:3312 net.physics:749 > > Can some thermodynamics whiz in net.physics clear this up? > > 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) Here is a model to work with, using convection cooling to cool the stillsuit, and evaporative cooling to cool the inhabitant. Consider these layers, working from the wearer out: 1 wearer 2 layer that lets water out, but insulates heat very well, and also prevents the water from getting back in. 3 water & humid air reservoir 4 layer that prevents water from escaping, but is a thermal conductor. 5 the outside environment The "human muscle power" here is used only to pump various substances around in the water & humid air reservoir for convenience (this is more like what Dune says they are used for). Layer 1 is cooled by evaporation. The heat from the evaporate is deposited in layer 3, which is in turn cooled by convection. Layer 3 is the hotest, layer 5 the next hotest, and layer 1 the least hotest :-). The key to making it work is the "magic" properties of layer 2. It allows water to pass one-way, and is a terrific thermal insulator. It may be that in order to have the properties I state, some energy would have to be expended... I'm not sure on this point. Someone has already mentioned the present-day desert-dweller's basic uniform, which covers essentially the entire body. My understanding of how it works is that it is layers 1-thru-3 from above. That is, the interior is cooled by evaporation, the evaporate is allowed to escape through porous clothing, and the clothing insulates against the now higher exterior temperatures. Without the added properties of layer 2 and layer 4, the "stillsuit prototype" used by current desert-dwellers must allow the water to escape. So: are the "magic" properties of layer 2 theoretically possible? If they are impossible in a simple sense, can it be done "with mirrors", that is, by clever (but minimal) expenditure of energy? If layer 2 could be made to work, it seems to me that stillsuits would work just fine. -- Wayne Throop at Data General, RTP, NC!mcnc!rti-sel!rtp47!throopw