121. Circulation pump is located below the evaporater to
Avoid cavitation
Avoid frequent priming
Create more suction head
None of these
✅ The correct answer is option C.
Heat Transfer MCQs
122. For a given ambient air temperature with increase in the thickness of insulation of a hot cylinderical pipe, the rate of heat loss from the surface would
Decrease
Increase
First decrease and then increase
First increase and then decrease
✅ The correct answer is option D.
123. In a heat exchanger, floating head is provided to
Facilitate cleaning of the exchanger
Increase the heat transfer area
Relieve stresses caused by thermal expansion
Increase log mean temperature gradient
✅ The correct answer is option C.
124. In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always
< 1
> 1
1
∞
✅ The correct answer is option A.
125. Vacuum is generally maintained in the vapour space of an evaporator mainly to
Get economical temperature difference by using moderate pressure steam
Facilitate forward feeding in multiple effect evaporation
Concentrate heat sensitive materials
Achieve very high concentration of the final product
✅ The correct answer is option A.
126. Small scale evaporation is done in a
Heat exchanger
Condenser
Multiple effect evaporator
Steam jacketed kettle
✅ The correct answer is option D.
127. For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are
Same
Different
Never different
Linearly related
✅ The correct answer is option B.
128. If Prandtl number is greater than the Schmidt number, then the
Thermal boundary layer lies inside the concentration boundary layer
Concentration boundary layer lies inside the thermal boundary layer
Thermal & concentration boundary layers are of equal thickness
Hydrodynamic(i.e., momentum)boundary layer is thicker than the other two
✅ The correct answer is option A.
129. The unit of heat transfer co-efficient in SI unit is
J/m²°K
W/m²°K
W/m°K
J/m°K
✅ The correct answer is option B.
130. Fouling factor
Is a dimensionless quantity
Does not provide a safety factor for design
Accounts for additional resistances to heat flow
None of these
✅ The correct answer is option C.