Half a croissant, on a plate, with a sign in front of it saying '50c'
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AC Economizer

Exchange unused coolth and warmth before expanding/compressing
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The idea is very simple. Start with a completely convention vapor compression air conditioner.

After the low pressure refrigerant has passed through the evaporator and turned completely to a gas, pass it through the economizer (a heat exchanger). In the economizer, the gas is superheated.

The next step is completely conventional, pass the refrigerant through the compressor and the condensor.

Last, pass the now liquid refrigerant through the economizer a second time, where it is subcooled. Then pass the extra cooled liquid through the expansion valve into the evaporator.

Due to superheating before compression, the refrigerant is raised to a higher temperature after compression than would have occured without superheating.

Due to subcooling before expansion, a smaller fraction of the liquid refrigerant flash-boils as it passes through the expansion valve, which results in a greater cooling capacity for each unit volume of refrigerant.

Thus, adding the economizer allows us to have a larger temperature differential with the same pressure differential, or the same temperature differential with a smaller pressure differential.

Either way, it should reduce energy consumption of the air condioner.

goldbb, Aug 10 2009


       //The next step is completely convetional//
AbsintheWithoutLeave, Aug 10 2009

       thx, I meant conventional, ordinary
goldbb, Aug 10 2009

       But this requires the input of extra energy for both the superheating of the gaseous refrigerant, and for the cooling of the liquid. One could be achieved by resistive heating elements, the other by Peltier-effect modules, but both still require extra energy.   

       "Welcome to Entropy (no free lunch)"
8th of 7, Aug 10 2009

       Assuming that the interior of the house is cooler than the exterior of the house, then the (gaseous) refrigerant coming out of the evaporator will inevitably be cooler than the (liquid) refrigerant coming out of the condenser.   

       Thus, when those two streams of refrigerant pass through a heat exchanger, the gaseous refrigerant *will* be warmed by the liquid refrigerant, and the liquid refrigerant *will* be cooled by the gaseous refrigerant.   

       No extra energy needs to be added.   


       By the term "superheating", I merely mean heating the gas to a temperature above it's boiling point... like the difference between "dry steam" and "wet steam."   

       It doesn't necessarily need to be to a super high temperature; in this case, the hottest the gas can posssibly be heated to is the temperature of the liquid coming out of the condensor.   

       Likewise, supercooling doesn't mean super cold. It merely means to below the liquid's boiling point. In this case, the coldest the liquid will be chilled to, will be the temperature of the gas coming out of the evaporator.
goldbb, Aug 13 2009

       There's nothing magic about this, but [goldbb]'s description is more complex than it needs to be. This is just a slightly larger evaporator and a slightly larger condenser. Arbitrary and certainly baked, but not magic.
Worldgineer, Aug 14 2009

       It's not "just a slightly larger evaporator and a slightly larger condensor." If it were, then the coolest that the condensed refrigerant could be would be the temperature of the air outside of the house; similarly, the hottest the gaseous refrigerant could be (before being compressed) would be the temperature of the air inside of the house.   

       Now, if you'd said, "gas turbine engines have heat exchangers which heat the compressed air (prior to combustion) using the exhaust air, improving efficiency, therefor it's reverse-baked," then I'd have agreed, since that is the most similar pre-existing technology. But you didn't, so I don't. :)
goldbb, Aug 17 2009


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