BUILDING A WALK IN COOLER/FREEZER

[DUMBDOG]

Has anyone built a walkin cooler or freezer? How much insulation? Source for refrigeration units, doors, etc.?

[MRB]

DD
sorry I just can't call you by your handle [img]/forums/images/icons/tongue.gif[/img] . I am surrounded by Amish families, some of them have home built walk-in freezers. Most of them are built from refrigerator units off of semi- trailers that haul produce and meats. They use solid foam insulation on a frame built box, or use an insulated box off of a smaller truck. Some use the power unit on the reefer and some have the diesel generators for their shops and businesses. If you know of any wrecker services in your area, you can probably buy a reefer unit from a wrecked semi-trailer.

[AndyF]

I've seen a few home-grown coolers which worked well for the market gardeners or small orchardists who used them. They were usually framed into a barn and had foamboard insulation for the floor, walls and ceiling. The doors were also homemade - 2X lumber frame, foamboard insulation and plywood skin.

A commercial evaporator unit was hung from the ceiling with the compressor and condenser mounted remotely. The refrigeration units can be bought through a company that services commercial refrigeration units.

If you look around you may also be able to pick up a used walk-in cooler when a restaurant goes out of business.

[AndyF]

Here's a link to a cooperative extension plan for a walk-in cooler, http://www.ag.ndsu.nodak.edu/abeng/plans/6380.pdf.

[Pat]

DD, I have designed some custom refrigeration and with the help of a good friend who is an excellant refrigeration mechanic, we built and successfully used the equipment. My favorite was a top loading "cooler" with an ice bank. It was insulated with the blue rigid foam insulaltion board and some hand fiberglass layup (no chopper gun). I used a free "throwaway" compressor out of a commercial ice machine. We used a cap tube system for simplicity rather than an expansion valve. The refrigeratiion coils (copper tubing) was immersed in a large water container at the bottom of the cooled volume. Copper strapping was soldered to the tubing every few inches to increase the area of contact between the water and the coils (for efficiency of heat transfer). The thermostat to control the compressor was in the ice bank. The thermostat in the "FOOD" chamber was conected to a small circulation fan. the compressor kept the ice bank at the desired temp. The circullation fan kept the food area at the desired temp. The controls were interactive and there was some seasonal variation but not too much. Starting with an old throw away compressor which we did nothing to improve, the system ran perfectly trouble free for 17 years and was still running perfectly 7 years after I sold it.

Why an ice bank? What is an ice bank? An ice bank stores "cold" like a giant thermal capacitor. Similar to the BLUE ICE for coolers at tailgating parties but we just used water. Could have improved performance with additives. We could sustain considerable power outages and not lose refrigeration. We didn't have to use a backup gen to run the compressor. For long outages running the circulalltion fans is a good idea and takes little power. Could be supplied by solar or ...

My design sounded a bit weird to my buddy who didn't want to waste time on a Rube Goldberg contraption (he is an excellent refrigeration mechanic but not an engineer. He likes to see something concrete, not calculations and my arm waving explanations) So we built a small prototype on the dock where we both lived on our respective boats. To his surprise, it worked fine. So we built a larger/real one on my sailboat to use as a refrigerator. In summer (SOCAL - San Diego), I could keep food real well for 10 days AFTER pulling the plug and heading to sea. Longer if we made port where I could plug it in. In winter, we got about 14 days without electricity.

The design is simple and scalable but only of interest if you are interested in refrigeration that laughs at a few days or a week or two of power outage.

Whatever you build, insulation and care in the details of installing insulation and paying attention to the laws of thermodynamics is important. I suggest you shop for the best R value/$ not the best R value/unit thickness for your insulation. Be especialy careful of thermal bridging and include provisions for defrost, washdown, etc. If you compartmentalize you can clean it a section at a time without shutting down.

Things to think of. In regular store bought systems they size the compressor not only has to overcome thermal leakage but to handle the heat introduced when adding unfrozen food. This requires you to have a fairly HD unit. With an ice bank, you store up cool like a bank account with automatic deposits. This stored cool handles surge load conditions and allows the use of a small efficient compressor. Super insulating the devil out of the design helps keep steady state delta T versus R value losses down so the small compressor can handle the average load. Average load rather than peak load becomes the important factor with this design. Given a large enough ice bank properly configured, and sufficient insulation, I could make a 100 sq ft room with 10 ft ceilings into a deep freeze with a compressor out of one of those little 2x2x2 ft (approx) AC friges that folks use in the office or at the wet bar for sodas. This would be darned cheap to run. It would require an air lock entry and properly configured
storage shelves. A pre-chill area with intimate ice bank access and a circulation fan would be used to get stuff frozen, then it could be filed away on a convenient shelf.

No waranty expressed or implied regarding the fitness for any specific purpose or the merchantability of this design discussion is implied, especially if you use it for low cost DIY human cryogenics purposes.

Pat