Cold storage

Barbie Dailey <barbiedailey [at] auroville__org__in> writes

>We are in the process of building a custom-made cold storage vault
>...
>... We are in a tropical climate (South India)
>by the coast where the external temperature ranges from 20-40 deg. C
>(70-104 deg. F) and relative humidity ranges between 50-95%
>averaging at 70%.
>
>Our proposed specifications for the vault are 10 deg. C +/- 2 deg. C
>and relative humidity at 45% +/- 5%.  We are told that it is
>difficult to maintain a stable RH below 10 deg. C.

I'll say. Considering the climate, you will have a challenge in
setting up the refrigeration system. Most (almost all) air
conditioning technicians understand cold storage for food (moist
cold) rather than dry cold storage. As you decrease the temperature,
handling the humidity gets more and more difficult. Reheat coils and
careful control and monitoring are very important, and few
technicians are experienced with either.

There is also the consideration of the expense of keeping the
temperature far below ambient temperature for the whole year. This
will be important both in the actual energy costs, and in the extra
cost for cooling capacity (a maximum 50 degree temperature
difference as opposed to 40 degree difference could make a big
difference in compressor and cooling coil size, plus an allowance
for the reheat coils).

I'm sure it would be advisable to try and keep the vault at a stable
temperature all year. So a good question first would be: What
humidity and temperature do you really need? Perhaps 20 degrees C
and a stable humidity all year would adequate for your needs, and
still be an exciting engineering challenge.  A secondary freezer
inside the vaults might be adequate in size for the sensitive
articles, and act as a "failsafe" for power outages and mechanical
breakdowns (they happen here!).

Your vault wall design must be take into account condensation. It
will happen, there are various solutions. Have you considered using
a pre-built, modular vault? They were suggested on the distlist a
few weeks ago when someone enquired about storing sensitive material
in a barn. I think it is a very good idea, someone in India must
make or import them.

Jerry Shiner
Keepsafe Systems


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                  Conservation DistList Instance 13:49
                 Distributed: Thursday, March 30, 2000
                       Message Id: cdl-13-49-006
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