Heat Transfer MCQs

Question 1

The actual temperature drop across the heating surface in an evaporator depends on the

Accepted Answer

All of the above

Answer

Feed

Answer

Depth of liquid over heating surface

Answer

Pressure difference between steam chest and vapour space

Question 2

Kg of liquid evaporated per hour in an evaporator is defined as its

Accepted Answer

Capacity

Answer

Economy

Answer

Steam load

Answer

None of these

Question 3

Mechanical recompression evaporation is used in the production of

Accepted Answer

Distilled water

Answer

Alcohol

Answer

Salt

Answer

Fruits jam

Question 4

Reason for operating an evaporator in multiple effect is to secure

Accepted Answer

Both A and B

Answer

Increased steam economy

Answer

Decreased steam consumption

Answer

Increased capacity

Question 5

In the equation Q = UAΔt; Δt is

Accepted Answer

Logarithmic mean temperature difference

Answer

Geometric mean temperature difference

Answer

Arithmetic mean temperature difference

Answer

The difference of average bulk temperatures of hot and cold fluids

Question 6

If Prandtl number is greater than the Schmidt number, then the

Accepted Answer

Thermal boundary layer lies inside the concentration boundary layer

Answer

Concentration boundary layer lies inside the thermal boundary layer

Answer

Thermal & concentration boundary layers are of equal thickness

Answer

Hydrodynamic(i.e., momentum)boundary layer is thicker than the other two

Question 7

Pick out the wrong statement.

Accepted Answer

Two identical cubes of iron and copper will have the same heat content under the same conditions of temperature

Answer

Economy of a multiple effect evaporator is not influenced by the boiling point elevation

Answer

Double pipe heat exchangers are mostly used in the field of refrigeration

Answer

Finned tube heat exchangers are suitable for heating air by steam

Question 8

Grashoff number, which is defined as g.β(Ts - T∞) ρ2.L3/μ2, is proportional to the ratio of buoyancy force to __________ force.

Accepted Answer

Viscous

Answer

Elastic

Answer

Inertial

Answer

None of these

Question 9

For __________ Prandtl number values, the heat conduction will be negligible in the buffer zone.

Accepted Answer

High

Answer

Extremely low

Answer

Low

Answer

No