Re: how to cool copper pipe

Dear jim:

cross-posting to sci.engr.mech

I guess this might be a good newsgroup for this > question. > > I want to make a cooling-unit more efficient by > cooling the copper suction pipe, ie: the pipe > that returns to the compressor and contains > high pressure freon or something similar (not > ammonia).

Be very careful. Compressors can be damaged by encountering a snootfull of liquid refrigerant on the intake. Increasing the cooling here would be counterproductive.

I was thinking that winding copper wire around the pipe might > act like a heatsink and > draw some heat away from the pipe, which would help lower the > pressure inside the pipe and > lessen the work for the compressor. That's the theory! > > But copper wire doesn't contact the pipe very well. I was > wondering if there is a better way > to actively or passively cool this pipe.

I think you need to review your basic cycles. On a refrigeration cycle:

1) gaseous refrigerant is drawn in and compressed, 2) the hot refrigerant gas is cooled across a condensor, 3) the warm refrigerant liquid has its pressure dropped across an orifice ("expansion valve"), 4) the cold refrigerant gas absorbs heat through the evaporator.

Increasing the effective size of the condensor will make your unit more efficient. But only to a point. Only so much liquid can go through the expansion valve, and a 2 deg difference in this liquid means very little additional cooling.

Keeping the correct pressures for the ambient-to-cold-space temperature difference will make it more efficient also.

I'd look at more efficient insulation, and leave the refrigeration cycle alone. You never know the damage you can do, or the quality of the person you will call in to service it.

David A. Smith