A freezer inside of a freezer inside of a freezer inside of a cooler insider a cooler

[Phase Loss]

The inner most freezer doesn't require defrost because there is 0% moisture in the air. The product is so temperature sensitive that it cannot raise 1* above its freezing point without being destroyed.

ever heard of it?

[codgy]

liquid nitrogen? or maybe CO2

[timebuilder]

The inner most freezer doesn't require defrost because there is 0% moisture in the air. The product is so temperature sensitive that it cannot raise 1* above its freezing point without being destroyed.

ever heard of it?

What kind of product would that be?

[Capz]

Unlikely as LIN & Liq co2 is relatively cheap and easily maintained in vacuum jacketed cryogenic vessels in the case of LIN and refrigerated or vacuum jacketed vessels in the case of co2. I would think the product in question would be medical research related.

[Phase Loss]

yeah it's a medical research facility.

[mspanky]

I use to take care of a blood bank. The freezer was nothing too fancy, just 2 compound Copelands with two evap coils with an auto switch-over if needed.

[Capz]

Liquid helium storage for MRI use

[Phase Loss]

i dunno what they got in there. For all I know its frozen alien eggs.

[ammoniadog]

I don't have any useful information to add, but what temperature range are you trying to achieve? Your Russian stacking dolls type of refrigeration scheme sounds crazy to me. Is this type of system commonly used for this type of application? Would the inner-most freezer be designed to only run if the other systems can't keep up for whatever reason, or would it basically be running all of the time?

[jpsmith1cm]

Interesting concept.

So, essentially, the outer "ring" of freezers act as a dehumidification system for the inner sanctum freezer only with shelves to store stuff on.

Neat. Wonder how many layers of redundancy are built into that system?

[Phase Loss]

I probably described it poorly. It's not a Russian stacking doll setup. it's one room after the next. Starting with coolers, then ending with freezers. Walk into one cooler...walk across the cooler, into the next cooler. Walk through that cooler to get into the first freezer and so fourth.

I've not been there yet. But supposedly the last freezer in the chain has 100% run time, no defrost.

redundancy, I dunno the setup. I know they have a backup generator.

[jpsmith1cm]

I can see it working.

[koolkahuna]

When I ran the HVAC/R department of our hospital, one of the freezers in the pharmacy was an ultralow temp cascade system. This freezer is set at -85 celsius/-120 fahrenheit.
It was purchased to allow extended use of a cancer killing drug. Normally a fraction of the drug($2700/vial) would be used for a patient and then the rest would be discarded. With the purchase of the ultralow freezer, the product could be used to its' full potential of six doses, which of course paid for the freezer about halfway through the first drug run.
The cascade system used the evaporator from the second system to remove heat from the first systems condenser allowing the first evap to absorb as much heat necessary to overcome almost all of the heat that was able to get through 8 inches of high quality insulation and a locking double door system.

Needless to say, the use of insulated gloves and eye protection is mandatory.

[Snapperhead]

When I ran the HVAC/R department of our hospital, one of the freezers in the pharmacy was an ultralow temp cascade system. This freezer is set at -85 celsius/-120 fahrenheit.

holy friggin ... can you imagine having to repair wiring problems on the evap in that kind of temp ?? Shiver me timbers ...

[koolkahuna]

holy friggin ... can you imagine having to repair wiring problems on the evap in that kind of temp ?? Shiver me timbers ...

Yeah, I always wanted to put one of my coworkers lunches in there and then put it back just before lunch. Problem is that if you dropped it, it would shatter!

[Tommy knocker]

Work on a system like that. Plasma center. Enter 1st box 0 degrees then into the two -40 degree storage boxes. Good setup.

[pecmsg]

But will you ever achieve 0% RH incoming air?

Isn’t that like reaching absolute 0?

[jpsmith1cm]

But will you ever achieve 0% RH incoming air?

Isn’t that like reaching absolute 0?

You don't need 0% RH. All you need to do is to get the dewpoint below evap temperature.

A good HVAC system and a couple layers of refrigeration surrounding it and I think that it is acheivable.

[jpsmith1cm]

Thinking further about it....

I don't have a problem with the humidity being reduced to a level that negates the need for defrost.

What I do think that you might have a problem with could be oil return.

[ammoniadog]

What if for whatever reason, it does need to be defrosted? Then what? Are you going to go in to a 100 below freezer (or however cold it is) with a hair drier or something? Or at that temperature, would the chance of it freezing up be slim enough that you really don't have to worry about it? After thinking about it, maybe whatever frost or ice that is in there would just sublimate away into nothing.

Relating to what Snapperhead said, though, what WOULD you do if something needed to be repaired in there? Do they have astronaut suits for you to wear or something? I'm guessing my Carhartt bibs and stocking cap wouldn't cut it in there.