# Nusselt Modulus - MCQs with Answers

## Nusselt Modulus – MCQs with Answers

1. The heat transfer is largely governed by conduction from the surface of the fluid, when

a. the velocity of the fluid is high
b. the velocity of the fluid is small
c. the velocity of the fluid is small as well as high
d. none of the above

ANSWER: b. the velocity of the fluid is small

2. Generally, thermal conductivity of liquids is

a. very high
b. very small
c. varies from very small to very high
d. unpredictable

3. In turbulent flow of the fluid,

a. conduction becomes more important
b. conduction becomes less important
c. doesn't matter
d. none of the above

ANSWER: b. conduction becomes less important

4. Mixing of fluid from regions of high temperature with the fluid from region of low temperature

a. increases the rate of heat transfer
b. decreases the rate of heat transfer
c. rate of heat transfer is not affected
d. none of the above

ANSWER: a. increases the rate of heat transfer

5. What does the Nusselt modulus or Nusselt number physically signify?

a. the ratio of the temperature gradient at the surface [(∂T / ∂y)y=0] to the reference temperature gradient [(Tw – T) / l]
b. the ratio of the reference temperature gradient [(Tw – T) / l] to the temperature gradient at the surface [(∂T / ∂y)y=0]
c. the sum of the temperature gradient at the surface [(∂T / ∂y)y=0] and the reference temperature gradient [(Tw – T) / l]
d. the sum of the reference temperature gradient [(Tw – T) / l] and the temperature gradient at the surface [(∂T / ∂y)y=0]

ANSWER: a. the ratio of the temperature gradient at the surface [(∂T / ∂y)y=0] to the reference temperature gradient [(Tw – T) / l]

6. The Nusselt modulus or Nusselt number is a convenient measure of

a. rate of heat transfer
b. convective heat transfer coefficient
c. both a. and b.
d. none of the above

ANSWER: b. convective heat transfer coefficient

7. What is the correct formula for the Nusselt modulus or Nusselt number (Nu)?

a. Nu = h k l
b. Nu = (h k) / l
c. Nu = (k l) / h
d. Nu = (h l) / k