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251.


Problem 26.15 (RHK)


An air conditioner takes air from a room at and transfers to the outdoors, which is at . We have to find out the amount in joules of heat transferred from the room for each of electrical energy required to run the refrigerator.


Solution:           Click For PDF Version

From the data of the problem we note that

We assume that the air conditioner is operating with maximum efficiency, which is the efficiency of a Carnot engine. For a Carnot refrigerator the work W done on the engine in each cycle and the heat absorbed at the lower temperature are related to the low and high temperatures as

Therefore,

We want find the heat absorbed from the room for each joule of electrical energy used by the refrigerator. We should calculate for . We find