491. __________ paint has the minimum absorption co-efficient.
Black
White lead
Grey
Light cream
✅ The correct answer is option B.
Heat Transfer MCQs
492. Nusselt number is the ratio of the
Temperature gradient of the wall to that across the entire pipe
Temperature difference to the temperature gradient at the wall
Heat flux at the wall to that across the entire pipe
None of these
✅ The correct answer is option C.
493. 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 = 0.6
(COP)R = 2.5; (COP)HP = 1.5
(COP)R = 1.5; (COP)HP = 2.5
(COP)R = (COP)HP = 2.5
✅ The correct answer is option C.
494. Which is the most suitable for cold viscous feed?
Forward feed
Backward feed
Mixed feed
Parallel feed
✅ The correct answer is option B.
495. In case of evaporators, liquid entrainment results primarily due to
High vacuum in the evaporator
High evaporation rate
Foaming of the solution
High heat transfer rate
✅ The correct answer is option C.