Adsorption air conditioners work on the same principle as vapor-compression units except they use heat and a small circulating pump to power the refrigerant instead of a compressor. An adsorption unit in a car would consume zero power, and the only drawback would be waiting for the car to heat up to cool down.
Ammonia-water adsorption has been around a long time, and the new zeolite adsorbers appear very promising. The gas saving would be substantial, and even the ecologists would be happy, because there would be fewer chloro-fluoro-carbons floating around.
So is Detroit looking at this? And why isn’t there an after-market kit to replace an A/C compressor with an adsorption unit? If space is a problem, just replace the compressor and the heater core with a water-to-adsorber or air heat exchanger.
If it’s using the heat from the engine, then it will draw power from the engine. Ultimately the engine will have to burn more gas to supply the energy the adsorption AC needs.
It still might be better than a regular AC, though.
If you wanted to get real fancy and use a refractory metal or ceramic heat exchanger, you could heat the adsorber with exhaust gas. I was thinking about using 180[sup]o[/sup]cooling water as the heat source, which is waste heat. If you don’t use it, it goes back to the environment thru the radiator. The circulating pump should draw no more current than the windshield wiper motor. The car would have the same power available, and get the same mileage whether the A/C was on or off.
I don’t know about adsorption a/c’s but from what you said I ass-u-me that:
you heat a gas or liquid which might cause a phase change, then cool it back to ambiant. as the substance reverts to it’s origional state it cools further.
If this is basically it then the reason that it is impractable for todays cars is that most people use their a/c on the highest setting when they 1st get in the car after it’s heated up in the sun - this is when you want the max cooling. then as you drive yu typically lower or turn off the a/c
It would seem that such an a/c would be good as a suplemental a/c but is the extra unit worth it?
It might be a better idea for busses or trains that run for some time (then again trains probally don’t produce enought heat in each car)
Would like to know more about the a/c adsorbtion system
Hold on. You are mixing two different things here. Adsorbents, like Zeolites, silica gels, and yes, even ammonia (although the others are solids) are used for dehumidification, but not cooling. If you are in a humid climate then dehumidification can decrease your cooling load, but it is not cooling. No sir. Not at all.
Absorption cooling, using ammonia or Lithium Bromide, is the technology you are looking for. An indirrect fired unit (using waste heat would have a COP of at most 1.0 or so, and in the size ranges found in cars I don’t think you could get even that. Plus the units are much larger and heavier than standard A/C.
The biggest problem would be city driving. While there is tons of waste heat when you are going 65 mph down the highway, when you are at a stoplight there isn’t that much, and there is no good way to store it in a car, so the A/C wouldn’t work then, unless you burned fuel directly, which would defeat the purpose.
ASHRAE has tons of good info on absorbers, as do all the big manufactures (Trane, Carrier, York, etc.) at their web sites. Take it with a grain of salt, though. They make big buck selling these things.
>> Adsorption air conditioners work on the same principle as vapor-compression units except they use heat and a small circulating pump to power the refrigerant instead of a compressor
Well,not really. Or thios is like saying “it is the same except where it is different”
At any rate, I am not going to write you a treaty here on adsorbtion heat transfer. just take my word for it if I tell you it is very inefficient and, on top of that, it would hardly work on a moving platform.
It is not used for home refrigerators or air conditioners because compressor heat pumps are better in every way. In a car this is even more true.