Heat and Mass Transfer Objective Questions with Answers - Set 10 - ObjectiveBooks

# Practice Test: Question Set - 10

1. Upto the critical radius of insulation,
(A) Added insulation will increase heat loss
(B) Added insulation will decrease heat loss
(C) Convective heat loss will be less than conductive heat loss
(D) Heat flux will decrease

2. Unit of thermal diffusivity is
(A) m²/hr
(B) m²/hr °C
(C) kcal/m² hr
(D) kcal/m. hr °C

3. The rate of energy transferred by convection to that by conduction is called
(A) Stanton number
(B) Nusselt number
(C) Biot number
(D) Peclet number

4. Thermal conductivity of wood depends on
(A) Moisture
(B) Density
(C) Temperature
(D) All of the above

5. A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100°C and leaves at 60°C. A cold fluid enters the heat exchanger at 40°C. The mean temperature difference between the two fluids is
(A) 20°C
(B) 40°C
(C) 60°C
(D) 66.7°C

6. The unit of overall coefficient of heat transfer is
(A) W/m²K
(B) W/m²
(C) W/mK
(D) W/m

7. LMTD in case of counter flow heat exchanger as compared to parallel flow heat exchanger is
(A) Higher
(B) Lower
(C) Same
(D) Depends on the area of heat exchanger

8. The transfer of heat by molecular collision is smallest in
(A) Solids
(B) Liquids
(C) Gases
(D) None of these

9. In heat exchangers, degree of approach is defined as the difference between temperatures of
(A) Cold water inlet and outlet
(B) Hot medium inlet and outlet
(C) Hot medium outlet and cold water inlet
(D) Hot medium outlet and cold water outlet

10. In a shell and tube heat exchanger, baffles are provided on the shell side to
(A) Improve heat transfer
(B) Provide support for tubes
(C) Prevent stagnation of shell side fluid
(D) All of these

11. An ordinary passenger aircraft requires a cooling system of capacity.
(A) 2 TR
(B) 4 TR
(C) 8 TR
(D) 10 TR

12. Joule sec is the unit of
(A) Universal gas constant
(B) Kinematic viscosity
(C) Thermal conductivity
(D) Planck's constant

13. Fourier's law of heat conduction gives the heat flow for
(A) Irregular surfaces
(B) Nonuniform temperature surfaces
(C) One dimensional cases only
(D) Two dimensional cases only

14. The value of Prandtl number for air is about
(A) 0.1
(B) 0.3
(C) 0.7
(D) 1.7

15. The product of Reynolds number and Prandtl number is known as
(A) Stanton number
(B) Biot number
(C) Peclet number
(D) Grashoff number

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