Building a Cold Plate System

Hello ---

I'm thinking of building a simple cold plate system for serving ice cream from a mobile cart, and I thought it might be good to bounce my ideas of some of the people here. I own the shop, so it's OK if it needs some tuning once it's built, but I'd like to come up with something safe that does the job. I'm certified, comfortable with welding and brazing, but definitely a beginner.

We make our ice cream (sorbet, really) in 1 quart round containers, about 4" diameter by 5" tall. I'm planning to build some custom 'plates' that have round insets that I can slide the canisters into, 6 canisters per plate. I'll use 8" deep food stainless steel food pans as the bottoms, and custom molded plastic forms for the tops.

We already do something similar at farmers' markets, but without the built in refrigeration. For that, we fill 6" deep the pans with a 10F salt water gel (ripped-open Cold Ice brand gel packs), freeze them in a freezer, and keep them in insulated boxes (Cambro Camcarriers). They stay frozen for most of the day, and keep the sorbet at a nice 12F - 15F serving temp (-10 C).

I'm thinking of using the same material as the eutectic solution in the cold plates, since I know it works. I'll run tubing through the sides of the pan, coil it around the indentations that the canisters will slide into, and fill it with gel. Epoxy the top down, and it's ready.

I'm thinking of using a small Danfoss condensing unit that's designed for a vending machine: UCHC0025RWB000B. It's a 1/4 hp unit for R404A. They'll be 3 pans, each filled with about 10 lbs of gel. If I'm reading things right, the specs say I should be able to freeze about 10 lbs per hour, so I'm pretty sure it should be able to refreeze solid if left overnight. If I insulate it well enough I'm pretty sure it will stay solid all day.

I'll have a TXV before the first pan, and join them all in series. I'm not sure what I'll need for controls. I'm guessing I can do well with a low pressure cut off on the suction line, since once it's set up it won't require much adjustment. And a high pressure switch for safety?

Elsewhere on this site, Peter_1 had a beautiful post where he suggested using a solenoid valve or a pumpdown approach on another system. The solenoid seems simplest --- I presume I'll be adding one after the receiver?

Some open questions:

Will I be OK with a salt water solution and copper pipes and silver solder in a stainless steel pan? I could go with all welded stainless steel instead, but that would be significantly harder to bend and build. In either case, what diameter tubing?

Will I do OK with a simple pressure control system and a solenoid that works opens whenever the compressor is on? Or is there benefit to using a full pumpdown system?

I'd like to keep a pretty narrow range on the temperature. A true phase change would be great, instead of a partial eutectic. Do any exist around -10C? Dodecane?

Thanks for any thoughts or suggestions!

Hmm, not a lot of response. I'm not sure if this is because I'm so far wrong no one has any idea where to start, or because cold plates are such a specialty item.

In any case, I've gone ahead and bought the compressor. I also ordered a copy of Nigel Calder's "Refrigeration for Pleasure Boats", as it seems to cover building custom cold plates.

Suggestions on tubing and controls still appreciated.

Stick to making ice cream and leave the refrigeration to the experts ;)

Dole refrigeration makes cold plates
http://www.doleref.com/plates.html