Thread: A/C Efficiency
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Old 09-03-2003, 06:06 PM
73MB280SEL 73MB280SEL is offline
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Join Date: Nov 2000
Location: Mustang, OK
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That really is very interesting. I am familiar with constant run systems, but I've never heard of this applied to automotive use. There are some inherent advantages to having the compressor run continuously. The most important one is that it saves wear and tear on the compressor. It also allows for continuous cooling to be available (no delay).

We are designing a constant run system for our radar. It is very tricky to make the compressor always run under all ambient conditions. To make this work, you have to EXACTLY balance the heat load to the cooling capacity. You also have to ensure that you don't return liquid freon to the compressor--very bad.

How we are doing it is with a discharge bypass valve. This works by venting hot compressor gas back to the suction side, raising its pressure. While this sounds very inefficient, it isn't as bad as you would think. Raising the suction side pressure naturally reduces cooling, keeps the evaporator from freezing, and lightens the load on the compressor.

Other systems work on the variable displacement principle by enabling/disabling the required number of cylinders.

What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.
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