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252.


Problem 26.17 (RHK)


(a) A Carnot engine operates between a hot reservoir at 322 K and a cold reservoir at 258 K. If it absorbs 568 J of heat per cycle at the hot reservoir, we have to find the work per cycle that it delivers. (b)We have to calculate the work per cycle that must be supplied for transferring 1230 J of heat from the cold reservoir, if the same engine, by working in reverse, functions as a refrigerator between the same two reservoirs.



Solution:           Click For PDF Version

From the data given in the statement of the problem, we note that

For a Carnot engine, we have

Heat absorbed by the engine per cycle at the hot-reservoir is 568 J.

Therefore, the work per cycle that the engine delivers, W, will be

(b)

For answering the second part of the problem, when the same Carnot engine works between the reservoirs in reverse that is it functions as a refrigerator, we use the result that the heat released to the hot-reservoir and the heat absorbed at the cold-reservoir in each cycle are related as

In the engine working as a refrigerator W is the work done on the engine per cycle. If the amount of heat that is to be transferred per cycle

the amount of work that must be supplied to the refrigerator per cycle will be