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Old 06-26-2021, 11:12 AM   #19 (permalink)
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Quote:
Originally Posted by serialk11r View Post
My idea is that the cycles don't really matter as much as the efficiency when the compressor is actually on. If the compressor is pumping too much refrigerant, its efficiency is reduced a lot. With reduced refrigerant charge, it is almost as if the compressor is spinning slower. You have more frictional losses from having to run the compressor more, but the gas cycle itself becomes more efficient. I know, not the best solution...it could be worse.

One idea I came up with for retrofitting a car with no A/C is cooled seats. Some people have modded their stock seats with air channels and fans, but you can also get an aftermarket fan cooled seat pad, and then add a heat exchanger with something so you can cool down the air. An inefficient way to do it is a Peltier cooler. You don't need that much cooling power to actually lower the air temperature to the point where it feels comfortable since the air flow is really slow.

Another way to do it is to use a duct on the car's stock vents and blow it through your seat, and then underdrive the pulley. Since your body is being directly cooled instead of the cabin, you don't need as much cooling capacity.

Yet another idea along the lines of reducing cooling capacity is a mini 12V compressor unit that blows directly on you or through a seat cooling pad. Alternator power is not efficient, but you would be drawing far less power overall compared to the original compressor.
Generally longer cycles at only the capacity needed are more efficient than an oversized system short cycling and is better for maintaining a consistent temperature. This is in part why many higher end home AC systems have inverter driven compressors and/or multiple stages.

I think the compressor's frictional losses are negligible compared to the losses from pumping refrigerant as an unloaded compressor spins pretty easily. I like the idea of underdriving the compressor except I don't want to lose significant cooling performance at idle since this car's AC has never cooled great at idle to begin with, even after I rebuilt the entire system.

I think upgrading to a larger and/or more efficient condenser would improve cooling capacity as well as efficiency since the high side pressure would drop, reducing the work the compressor needs to do. I would need to take some measurements, but there is definitely room for a bigger and thicker condenser. The biggest problem would be that I'm sure having a custom condenser made would be very expensive and I likely wouldn't be able to find an aftermarket condenser that would fit and be better enough to be worth buying and having custom AC lines made to be able to use.

I like the cooled seat idea, but unfortunately I wouldn't be able to use it instead of AC as I have asthma and breathing hot humid air for extended periods of time doesn't work for me.
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