Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!know!news.cs.indiana.edu!rutgers!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: dmocsny@minerva.che.uc.edu (Daniel Mocsny) Newsgroups: sci.nanotech Subject: Re: What will nanotech-economy mean to the world? Keywords: efficiency, 2nd law, greenhouse effect, space exploration Message-ID: Date: 6 Dec 90 07:44:11 GMT Sender: nanotech@athos.rutgers.edu Organization: University of Cincinnati, Cin'ti., OH Lines: 51 Approved: nanotech@aramis.rutgers.edu In article ningluo@acsu.buffalo.edu (Ning Luo) writes: >[Wrong! A much better heat sink, both from thermodynamic and > environmental perspectives, is the 3K intergalactic background. > It can be accessed from right here on cloudless nights, and > from LEO all the time. > --JoSH] The only commercially competitive terrestrial application of which I know for this heat sink is producing ice in 3rd-world countries. (Place a shallow pan of water on top of a building or hilltop so it only "sees" the night sky. Insulate the bottom. On a calm, clear night, the water can radiate enough heat into space to freeze solid even if the air temperature is above freezing.) Radiative heat transfer across small temperature differences is very slow compared to the mechanisms of conduction and convection. Virtually all heat transfer in the process industries is by a combination of those two. In most practical heat exchanger design, radiation is minor enough to neglect. The consequence is that large-scale power generation today requires convenient heat sinks, such as rivers, oceans, and/or cooling towers. Any scheme that relied on direct radiation to space would need massive arrays of radiators and long runs of piping for all the working fluid. That in itself would probably have an environmental impact considerably greater than the impact of dumping the waste heat into the atmosphere. Just because something is theoretically available does not mean that it will be practical. I have never heard of a serious suggestion to use direct radiation to space to cool a terrestrial power plant. The problem with problematic waste is not that we *can't* deal with it, but that we can't get rid of it without generating even more waste. -- Dan Mocsny Snail: Internet: dmocsny@minerva.che.uc.edu Dept. of Chemical Engng. M.L. 171 dmocsny@uceng.uc.edu University of Cincinnati 513/751-6824 (home) 513/556-2007 (lab) Cincinnati, Ohio 45221-0171 [This underscores Mr. Luo's major point that we must get out into space, which I enthusiastically support. However, I must point out that all terrestrial conductive and convective heat sinks ultimately feed into the dark sky: it is the real sink, and the planet only a buffer. With that in mind, it's clear that we could build (in space) a radiative cooler with half the area of the earth which could sink all the contact- with-matter sunk power theoretically capable of being generated on earth. From there it's only a giant leap to a Dyson sphere... --JoSH] Brought to you by Super Global Mega Corp .com