Heat Transfer
For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it

Increases the overall heat transfer coefficient
Decreases the pressure drop
Decreases the outlet temperature of cooling medium
None of these

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

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