Heat Transfer MCQs

Question 1

A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to

Accepted Answer

D-0.2

Answer

D0.8

Answer

D-1

Answer

D-1.8

Question 2

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzman constant = 5.67 × 10-8 W/m2.K4)

Accepted Answer

1000

Answer

727

Answer

800

Answer

1200

Question 3

Crystal size in a continuous crystalliser depends upon the

Accepted Answer

All of the above

Answer

Rate of heat transfer

Answer

Degree of turbulence

Answer

Degree of supersaturation

Question 4

For heat flow through very thick walled cylinder, use____mean radius.

Accepted Answer

Logarithmic

Answer

Arithmetic

Answer

Geometric

Answer

Either A or C

Question 5

In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell)

Accepted Answer

0.75 D

Answer

0.25 D

Answer

0.50 D

Answer

None of these

Question 6

Tube pitch is the __________ of tube diameters and the clearances.

Accepted Answer

Sum

Answer

Difference

Answer

Ratio

Answer

None of these

Question 7

The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, $$\Delta {	ext{T}}$$ = Temperature drop across condensate film)

Accepted Answer

$${\left( {\Delta {	ext{T}}} ight)^{\frac{1}{4}}}$$

Answer

$${\left( {\Delta {	ext{T}}} ight)^2}$$

Answer

$$\sqrt {\Delta {	ext{T}}} $$

Answer

$${\left( {\Delta {	ext{T}}} ight)^{\frac{3}{2}}}$$

Question 8

Multiple effect evaporators ar used to

Accepted Answer

Increase the steam economy & the capacity

Answer

Increase the steam economy & decrease the capacity

Answer

Decrease the steam economy & the capacity

Answer

Decrease the steam economy & increase the capacity

Question 9

Pick out the wrong statement.

Accepted Answer

Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film co-efficient, which is higher

Answer

The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation

Answer

Film co-efficient for vaporisation decreases as a result of vapor binding

Answer

In industrial practice, sub-cooling of condensate is required, when the condensate is a volatile liquid and is to be transferred for storage