Twin Compressor Efficiency

[Inalex]

I posted in the books section looking for some texts on energy efficiency in small box refrigerators and freezers and didn't get much yet. Thinking about the information I wanted got me to thinking about an old idea.

I am prepared for this to be shot down instantly.

If money were no object and energy efficiency were the prime concern I think that two compressors and evaporators within the same box should be considerably more efficient than a similar single system.

Most of the time a small compressor with passive cooling and convection distribution within the box would run at its most efficient. When the box was opened or filled with warm produce the internal temp rise would kick in the larger compressor with air blown cond. and evap. until the temp was pulled down.

Anyone see the glarnig holes that are no doubt in this plan?

[star882]

Actually, one of the easiest ways to save energy is to make the door open from the top so little cold air falls out when the door is opened. And if the temperature is a good amount over freezing, defrost can be done by just turning off the compressor and letting the ice melt. If the temperature is below freezing, the evaporator can be designed as a cylindrical plate with close tolerance blades inside. A motor runs for a few seconds every hour or so to scrape off the frost.

As for the compressors, I think it would be more cost effective to just put them in parallel, use a solenoid valve to switch in a high capacity expansion valve, and design the system for good oil return.