Heat and Mass Transfer - Set 02 - ObjectiveBooks

# Practice Test: Question Set - 02

1. Heat transfer in liquid and gases takes place by
(A) Conduction
(B) Convection
(D) Conduction and convection

2. The heat transfer takes place according to
(A) Zeroth law of thermodynamics
(B) First law of thermodynamics
(C) Second law of thermodynamics
(D) Kirchhoff's law

3. Which of the following is the case of heat transfer by radiation?
(A) Blast furnace
(B) Heating of building
(C) Cooling of parts in furnace
(D) Heat received by a person from fireplace

4. Thermal conductivity of water _________ with rise in temperature.
(A) Remain same
(B) Decreases
(C) Increases
(D) May increase or decrease depending upon temperature

5. Heat is closely related with
(A) Liquids
(B) Energy
(C) Temperature
(D) Entropy

6. The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is
(A) Equal to one
(B) Greater than one
(C) Less than one
(D) Equal to Nusselt number

7. Pick up the wrong case. Heat flowing from one side to other depends directly on
(A) Face area
(B) Time
(C) Thickness
(D) Temperature difference

8. The critical radius is the insulation radius at which the resistance to heat flow is
(A) Maximum
(B) Minimum
(C) Zero
(D) None of these

9. Metals are good conductors of heat because
(A) Their atoms collide frequently
(B) Their atoms are relatively far apart
(C) They contain free electrons
(D) They have high density

10. The automobile radiator is a heat exchanger of
(A) Parallel flow type
(B) Counter flow type
(C) Cross flow type
(D) Regenerator type

11. Which of the following is a case of steady state heat transfer?
(A) I.C. engine
(B) Air preheaters
(C) Heating of building in winter
(D) None of the above

12. Which of the following would lead to a reduction in thermal resistance?
(A) In conduction, reduction in the thickness of the material and an increase in thermal conductivity.
(B) In convection, stirring of the fluid and cleaning the heating surface.
(C) In radiation, increasing the temperature and reducing the emissivity.
(D) All of the above

13. Total heat is the heat required to
(A) Change vapour into liquid
(B) Change liquid into vapour
(C) Increase the temperature of a liquid or vapour
(D) Convert water into steam and superheat it

14. The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to
(A) -1/3
(B) -2/3
(C) 1
(D) -1

15. Cork is a good insulator because it has
(A) Free electrons
(B) Atoms colliding frequency
(C) Low density
(D) Porous body

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