From: Stephen J. Van Sickle (sjvans@ameritech.net)
Date: Sun Jul 14 2002 - 02:11:45 MDT
On Sun, 2002-07-14 at 00:48, spike66 wrote:
> So, does anyone know what the largest temperature delta is in
> the dewar? I am amazed if it is greater than 5C. spike
I've been looking for the exact numbers but cant fing them just yet, but
just can't find them. Bear in mind 2 things:
90% of the heat lost in the bigfoot dewars are through the neck and the
cork. This creates a strong heat gradient along the top to bottom, and
the dry air over the liquid surface is very cold, dense, dry, and still
and so is very insulating.
This gradient is commonly used in tissue sample storage, in what is
called "vapor phase" storage...even a few inches over the puddle of LN2
at the bottom, temps increase 20C to 50C, giving the samples both
slightly warmer storage and eliminating risk of cross-contamination.
This is more or less the approach we are looking at for higher
temperature storage, with extra help (foam) to stop the gradient at just
the right temperature, and fans to even out the temp in the vapor phase
at exactly what we want. 90% passive, 10% fine control active.
steve van sickle
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