X-Message-Number: 1995 Date: Fri, 19 Mar 93 13:10:05 CST From: Brian Wowk <> Subject: CRYONICS K values Steve Harris: > I assumed one foot thick foam, but used a K of ~ 0.01 watt/m*K, which > was the number I got for the best cryogenic foams used in insulating > the non-Dewar tanks of liquid fuel cryogen rockets, like the > space shuttle (NASA reprint #1002). I started from the room-temperature R value of Dow Styrofoam (quoted to me by a dealer), which is 5 per inch. This corresponds to a room-temperature conductivity of 0.028 watt/m*K. Considering that the thermal conductivity of a gas varies as the square root of the absolute temperature, this value scaled to a point midway between 20'C and -130'C comes out to be 0.024 watt/m*K. Polyurethane foam, with R = 5.9, would be only 20% better. It would be useful to know what K value Hugh Hixon used to successfully predict the performance of the Trymer cool-down boxes. --- Brian Wowk Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=1995