X-Message-Number: 2241 Date: 12 May 1993 08:29:35 -0700 (MST) From: Subject: CRYONICS Cold Room Problems In Cryomsgs #2235 and #2236, Brian Wowk and Charles Platt mention some potential problems with the idea of putting the present dewars in the cold room. Charles points out that the dewars are quite tall (9 ft. or so) and therefore the cold room ceiling would need to be higher than that in a typical room. This is not a problem, since of course the room could be built with such a ceiling height, and in fact this is probably desirable for a room of reasonable size (say 12 ft. x 12 ft. or larger). To minimize heat leakage into the room it should have a low surface-to-volume ratio, meaning (for a room with flat walls) as near a cubical shape as practicable. Charles also says that the added expense of duplicating the dewars (double insulation) is not justified. But we already have purchased the dewars; presumably once we got the cold room up and running we would no longer offer the option of storage in LN2; therefore we would no longer be buying new dewars. Finally, Brian brings up the most important potential problem: a "loss of coolant accident" inside the room if one of the dewars was to lose vacuum and dump its load of LN2 rapidly into the room. Presumably, the room will be monitored by a live human, the patients would not be left unattended on autopilot. If vacuum was lost, well before all the LN2 was lost, it could be drained out of the room: I assume the floor of the room will have a drain. What would happen now if one of our dewars was to lose vacuum? Patients would certainly be at risk! At least if the dewar was in a 135K environment, no one would be at risk of meltdown. --Mark Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=2241