heat transfer MCQs – Page 3

Practise focused heat transfer questions with marked answers for exam preparation and subject revision.

heat transfer Mcqs
41. Unit of thermal diffusivity is_________________?
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A. kcal/m2 hrC

B. m2/hr

C. m2/hrC

D. kcal/m.hrC

E. kcal/m2 hr

42. Heat flowing from one side to other depends directly on ___________________?
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A. k up the wrong case?

43. Fouriers law of heat conduction is valid for_________________?
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A. regular surfaces having non-uniform temperature gradients

B. two dimensional cases only

C. one dimensional cases only

D. three dimensional cases only

E. irregular surfaces

44. Heat is closely related with___________________?
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A. liquids

B. enthalpy

C. entropy

D. energy

E. temperature
45. According of Kirchhoffs law______________________?
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A. emissive power and absorptivity are constant for all bodies

B. ratio of emissive power to absorptive power is maximum for perfectly black body

C. ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body

D. radiant heat is proportional to fourth power of absolute temperature

E. emissive power depends on temperature

46. Which of the following has maximum value of thermal conductivity________________?
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A. brass

B. aluminium

C. lead

D. copper

E. steel

47. Unit of thermal conductivity in S.I. units is__________________?
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A. B. and C. above

B. J/m K sec

C. J/m2 sec

D. A. and C. above

E. W/m K

48. In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by___________________?
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A. convection

B. radiation

C. conduction

D. both convection and conduction

E. none of the above

49. Heat transfer in liquid and gases takes place by_____________________?
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A. conduction and convection

B. radiation

C. convection

D. convection and radiation

E. conduction

50. Moisture would find its way into insulation by vapour pressure unless it is prevented by __________________ ?
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A. less thermal conductivity insulator

B. all of the above

C. high thickness of insulation

D. high vapour pressure

E. a vapour seal
51. Thermal conductivity of wood depends on_______________?
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A. all of the above

B. density

C. none of the above

D. temperature

E. moisture

52. Which of the following has least value of conductivity_________________?
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A. glass

B. air

C. plastic

D. rubber

E. water

53. A grey body is one whose absorptivity_________________?
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A. varies with temperature

B. does not vary with temperature and. wavelength of the incident ray

C. varies with wavelength of the incident ray

D. is equal to its emissivity

E. none of the above

54. Thermal conductivity of solid metals with rise in temperature normally___________________?
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A. increases

B. unpredictable

C. remains constant

D. decreases

E. may increase or decrease depending on temperature

55. When heat is Transferred by molecular collision, it is referred to as heat transfer by __________________?
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A. convection and radiation

B. radiation

C. convection

D. scattering

E. conduction
56. Heat transfer takes place as per ________________?
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A. first law of thermodynamic

B. zeroth law of thermodynamics

C. second law of the thermodynamics

D. Kirchoffs law E. Stefans law

57. The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as_________________?
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A. Krichoffs law

B. Black body law

C. Wien law

D. Stefans law

E. Plancks law

58. In regenerator type heat exchanger, heat transfer takes place by___________________?
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A. a complete separation between hot and cold fluids

B. generation of heat again and again

C. direct mixing of hot and cold fluids

D. indirect transfer

E. flow of hot and cold fluids alternately over a surface
59. The emissive power of a body depends upon its___________________?
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A. wave length

B. physical nature

C. all of the above

D. temperature

E. none of the above

60. Total emissivity of polished silver compared to black body is___________________?
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A. more or less same

B. very much higher

C. higher

D. same

E. very much lower