321. The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the
Heating volume
Heat transfer area
Nusselt number
None of these
✅ The correct answer is option B.
Heat Transfer MCQs
322. In forced convection, the Nusselt number is a function of
Re and Pr
Re and Gr
Pr and Gr
Re and Sc
✅ The correct answer is option A.
323. In which mode of heat transfer, the Biot number is important?
Transient heat conduction
Natural convection
Forced convection
Radiation
✅ The correct answer is option A.
324. Viscous & heat sensitive liquids are concentrated in __________ evaporators.
Open pan
Long tube
Agitated film
None of these
✅ The correct answer is option C.
325. A black body when hot, emits heat radiation of __________ wavelengths.
Small
Large
All
One fixed
✅ The correct answer is option C.
326. Steam economy in case of a triple effect evaporator will be
1
< 1
> 1
Between 0 and 1
✅ The correct answer is option C.
327. A dephlegmator is a
Total condenser
Vacuum evaporator
Partial condenser
Double pipe heat exchanger
✅ The correct answer is option C.
328. Water always boils when its
Temperature reaches 100° C
Vapour pressure equals 76 cm of Hg
Saturated vapour pressure equals the external pressure on its surface
Saturated vapour pressure is less than the atmospheric pressure
✅ The correct answer is option C.
329. In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be
Less than 45°C
More than 45°C
Equal to 45°C
Initially decreases and remains constant thereafter
✅ The correct answer is option B.
330. 1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C.
1.49
1
4.88
None of these
✅ The correct answer is option A.