Re: Dry Ice payload testing


steve potter
 

I would also like to chime in and say a small battery powered fan would likely increase the distribution of the cold air, even in a cooler there will be a difference in temperature from the top to the bottom of it, some kind of circulation would likely help.


On Sun, May 2, 2021, 8:57 PM Michael Hojnowski <kd2eat@...> wrote:
Hey Gang,

Does anyone have much experience in cold-testing payloads with dry
ice?   A few students on our team tried to use dry ice for a test, and
didn't have much luck.  The objective is to try and test the payload box
in very cold exterior temperatures to see if the interior can be kept
warm.  They have an experiment that won't tolerate cold very well.  The
initial attempt was to use a small battery powered hand warmer (which
has a thermostat to keep from getting too warm) inside the payload box
to keep the temperature around 70f.  The "hoped for" outcome was that
they would measure some very cold (-40ish) temps outside the payload
box, but that the interior would remain toasty warm.   In practice, the
test didn't work out so well.

I didn't see the test, but they apparently got 8 pounds of dry ice and
put it in a large cooler.  They put the payload box in the cooler, and
ran some thermocouples into the payload box and surrounding container. 
The larger cooler was a snug fit around the payload box.

They left it closed for an hour, and the "outer cooler" temp only went
down to about 7c.  Unfortunately, the payload box interior temp went
down to just about the same during the test.  Apparently, the hand
warmer failed at some point during the test.

They'd like to be able to create very cold conditions outside the
payload box (colder than 7c) while they sort out the interior heating
issue.

If anyone has some experience, war stories, or scars they can share, the
team would appreciate it.

Thanks!
Mike





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