Hey guys, I'm in the process of fleshing out some design details for a liquid chiller project for a thermal systems design course at school and am wondering if anyone has some advice for what refrigerant would be practical.

We get 7 min to cool a 500 mL bottle of water as much as possible using a bucket of ice water with between 4 and 8 lb of ice. I'm working on determining what sort of system will be able to completely freeze the bottle before 7 min so as to reach a final temp lower than freezing. My preliminary calculations show I'm looking for at least an 800W system with an evaporator temp probably between -20 and -30 degrees C in a glycol liquid bath. The condensor will be a shell and tube HX with the water from the icebucket circulated through it, hence very cold condensor temps.

So my question is, would R-22 be a practical choice in this case? Is there another non exotic refrigerant that would work better? I'm trying to find a solution that does not require a huge compressor (R-134a and R-152a have been ruled out in favor of R-22 so far for this reason, going by the research I've done so far). I'm also trying to limit it to any relatively common refrigerants to keep cost and complexity down (primarily sourcing major components from scrap equipment/ebay, meaning selection is limited to mostly common stuff, plus whatever else that common stuff could be made to work with, like what refrigerants have a chance of working well in an R-22 compressor).

I do have my 608 type 1 certification, so legality is squared away.

Thanks in advance!