X-Message-Number: 6636
Date: Sun, 28 Jul 1996 19:04:46 -0700
From: Tim Freeman <>
Subject: Stable temperature without LN2 (was cryostat variants)

From: Doug Skrecky <>
> Water/ice will stay near 0 C till all the ice is melted. Perhaps a
> liquid which freezes at around -150 would fit the bill. Freon 12 for
> example freezes at -158, yet boils only at -29. For a cryostat
> containing a mixture of solid/liquid freon 12 the temperature of -158
> would effectively preclude expensive boiloff. Liquid freon could be
> drained periodically from the cryostat, refrozen and then added back
> inside. 
>
> Another possibility would be to use sorbitol or some other "solid" 
> cryoprotectant with a glass transition greater than -78 so that then
> cold storage could use dry ice. 

In the discussion about a cold room on this list a few years ago, the
conclusion was that water is so much cheaper than everything else that
it makes sense to put lots of buckets of water ice in the room.  This
doesn't have any special behavior at any interesting temperature, but
it absorbs heat with little temperature change so well, and it's easy
to afford so much of it, that the cold room with an affordable amount
of water ice for ballast could have stayed at a reasonable temperature
for a month or so with the cooling system powered down.


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