Water-cooled lander |
Water-cooled lander |
Aug 22 2007, 05:22 PM
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#1
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Member Group: Members Posts: 214 Joined: 30-December 05 Member No.: 628 |
There is a recent posting on Emily's Planetary Society blog, which must be Doug's because she's not there herself, although her name is the only name on it. The subject is using water to cool a long-lived surface probe on Venus. It sounds far more practical than any of the other proposals for landing giant atomic-powered refrigerators, or developing a whole new family of high-temperature semiconductors, etc.
But I didn't understand the whispered criticism to the effect that the Ekonomov paper assumed that the water would absorb heat only from the one watt of power driving the instrument package itself. I simply can't believe that he went to the podium and presented his model without taking into account the fact that the surface of Venus is a pretty hot place, and that the proposed probe would be absorbing the ambient heat. This is an interesting proposal and I would like to understand both the original calculation of 50 days to bring the water to a boil, and the cited flaw in the calculation. I too find it hard to believe that it would take 50 days to bring water to a boil on the Venusian surface, but where exactly is the error, and what remains after we correct it? Doug is busy of course, but I hope he will find the time to address this when he returns, if someone else hasn't done so by then. |
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Nov 7 2007, 07:05 PM
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#2
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
The problem is that the latent heat of evaporation of water is so huge -I don't know of anything else that can match it.
Doug |
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Nov 7 2007, 10:01 PM
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#3
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Newbie Group: Members Posts: 9 Joined: 6-November 07 From: USA, MN Member No.: 3954 |
The problem is that the latent heat of evaporation of water is so huge -I don't know of anything else that can match it. Doug Well yes water does have a very high heat of fusion and specific heat capacity. But others come close for example it would take water 34.8 hr to go from -20 to 60C with 500 watts of input heat, for formic acid it would take 24.5hr, and if formic acid has a much small density difference between it phases (can't find density of solid phase formic acid) you could get a weights savings by using formic acid without the need for another containment layer/vessel. --nny |
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