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Smarter, stronger air conditioning on its way?

by David Zatz on

Have you ever been annoyed that your air conditioner wasn’t working well on hot days, when you have to stop for a traffic light and the engine is barely ticking over?

It’s worse in a car with an engine stop-start system. The air conditioning remains somewhat effective, because it takes time for the evaporator to warm up, but on very hot days, the engine has to stay on more, and work harder, to cool the cabin.

A recent Fiat Chrysler patent by Michigan’s Matthew Bartlett may fix both problems. He proposed an air conditioner which, in essence, stores cold when the car is coasting or braking, and can release it when the engine stops or idles.

Air conditioners work by compressing a gas to force it into a liquid state, which heats it up; then they let the liquid expand, in the evaporator, which cools it down. A fan blows air from the evaporator into the cabin, while the condenser sits under the hood and is cooled by air flowing through the engine bay.

start-stop system

Bartlett’s system adds a “storage evaporator.”  It “charges” when the vehicle is coasting or idling, by circulating cold refrigerant which changes the phase of internal materials. The  storage evaporator discharges when the engine is off, so the cabin can be cooled as the material changes phase back again. (The phase change is, as one example, freezing a material to a solid.)

This doesn’t reduce the power demands of the air conditioner, but it does build up a reserve of coldness, so to speak. That would make a stop-start system far more comfortable and effective, because on hot days, the air conditioner and engine would have to run less to cool the cabin.

Bartlett’s innovation in air conditioning could increase comfort while saving a great deal of gasoline across FCA’s fleet of stop-start cars — and increase the company’s fleet economy ratings. Courtesy Steven St. Laurent.

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