Heat Transfer
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are

(COP)R = 1.5; (COP)HP = 2.5
(COP)R = (COP)HP = 0.6
(COP)R = (COP)HP = 2.5
(COP)R = 2.5; (COP)HP = 1.5

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Heat Transfer
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because

Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect
Total heat transfer area of all the effects is -less than that in a single effect evaporator system
Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system
Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system

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