chemical engineering heat transfer chemical engineering Mcqs
51. Corrosiveness of steam condensate is due to the presence of________________?
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A. CO2

B. Dissolved O2

C. Both A. & B.

D. Neither A. nor B.

52. Heat transfer by ____________ may not necessarily require the presence of a medium?
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A. Forced convection

B. Natural convection

C. Conduction

D. Radiation
53. View factor is important in heat transfer by_____________________?
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A. Natural convection

B. Steady state conduction

C. Radiation

D. Forced convection

54. The thermal boundary layer at NPr > 1 ?
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A. Is thinner than hydrodynamic boundary layer

B. Is thicker than hydrodynamic boundary layer

C. Disappears

D. And the hydrodynamic boundary layers are identical

55. Radiation heat losses from satisfactorily insulated high pressure boiler may be about _____________ percent?
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A. 1

B. 26

C. 18

D. 7
56. Vent pipes are provided in a condenser to ________________?
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A. Facilitate easy cleaning of tubes

B. Remove non-condensable gases

C. Purge the condenser

D. None of these

57. Multipass heat exchangers are used______________________?
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A. To obtain higher heat transfer co-efficient and shorter tube

B. For low heat load

C. Because of simplicity of fabrication

D. To reduce the pressure drop

58. Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the________________?
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A. High heat transfer co-efficient

B. Less corrosion problems

C. Low pressure drop

D. Flexibility possible in the baffle arrangement
59. In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used________________?
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A. In low range of temperature differences

B. To prevent corrosion of the tube bundles

C. Because of its low cost

D. In high range of temperature differences
60. Heat transfer rate described by Fouriers law will decrease, if the _____________ increases?
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A. Heat transfer area

B. Temperature difference

C. Thickness

D. Thermal conductivity

61. When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as ___________________ boiling?
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A. Transition

B. Nucleate

C. Film

D. Pool

62. The rate of emission of radiation by a body does not depend upon the__________________?
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A. Nature of the surface

B. Surface temperature of the body

C. Shape and porosity of the body

D. Wavelength of radiation

63. In sub-cooled boiling ?
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A. Bubbles from heating surface are absorbed by the mass of the liquid

B. Temperature of the heating surface is more than the boiling point of the liquid

C. Very large vapour space is necessary

D. Temperature of the heating surface is less than the boiling point of the liquid

64. The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is ________________?
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A. 2

B. 2-Jan

C. 1/4

D. 4

65. The overall resistance for heat transfer through a series of flat resistance, is the _____________ of the resistances?
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A. Product

B. Sum

C. Geometric mean

D. Average

66. Kirchoffs law is applicable to________________?
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A. Monochromatic radiation only

B. Total radiation only

C. Both A. and B.

D. Only volumes and not to surfaces

67. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _____________ law?
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A. Hyperbolic

B. Linear

C. Logarithmic

D. Parabolic
68. The driving potential for the crystal growth during crystallisation is the _______________ of the solution?
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A. Super-saturation

B. Density

C. Concentration

D. Viscosity

69. Grashoff number is given by________________?
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A. gD2??t?/?2

B. gD3??tP2/?

C. gD3.?.?t?2/?2

D. gD2??tP2?

70. Heat flux, as defined in heat flow is analogous to _______________ in electricity flow?
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A. None of these

B. Voltage

C. Current

D. Resistance

71. In Fouriers law, the proportionality constant is called the______________________?
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A. Heat transfer co-efficient

B. Thermal conductivity

C. Stefan-Boltzmann constant

D. Thermal diffusivity

72. What is the logarithmic mean of r1 and r2 ?
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A. (r1 r2)/ln(r2/r1)

B. (r2 r1)/ln(r1/r2)

C. (r1 r2)/-ln(r1/r2)

D. (r1 r2)/ln(r1/r2)
73. In a shell and tube heat exchanger, floating head is used for _________________?
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A. Low pressure drop

B. High heat transfer co-efficient

C. Less corrosion of tubes

D. Large temperature differentials
74. Cp?/K is termed as the ______________ number?
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A. Stanton

B. Nusselt

C. Prandtl

D. Grashoff

75. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is__________________?
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A. 4.36

B. Dependent on NRe only

C. 2.36

D. 120.36

76. A steel sphere of radius 0.1 m at 400K is immersed in an oil at 300K. If the centre of the sphere reaches 350K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions? Assume that the conductive heat transfer co-efficient is infinitely large ?
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A. 5 minutes

B. 20 minutes

C. 10 minutes

D. 40 minutes

77. Heat exchanger tubes are never made of_________________?
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A. Plain carbon steel

B. Copper

C. Stainless steel

D. Lead
78. Economy of a multiple effect evaporator depends upon the _____________________?
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A. Heat balance consideration

B. Rate of heat transfer

C. Both A. and B.

D. Neither A. nor B.

79. Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?
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A. Density

B. Corrosiveness & fouling characteristics

C. Pressure

D. Viscosity

80. Steam trap is used to_________________?
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A. Remove water resulting from partial condensation of steam

B. Stop the supply of steam

C. Condense the steam flowing in the pipeline

D. None of these

81. The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
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A. ? 1/T

B. Independent of T

C. ?T

D. ? T4

82. A black body does not ____________ radiation?
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A. Absorb or emit

B. Refract

C. Reflect

D. Both B. & C.
83. At constant temperature, the thermal conductivities of gases _____________ with rise in pressure?
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A. Decrease

B. May increase or decrease; depends on the pressure

C. Remain unchanged

D. Increase

84. Reason for operating an evaporator in multiple effects is to secure ___________________?
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A. Increased steam economy

B. Decreased steam consumption

C. Both A. and B.

D. Increased capacity

85. Forced circulation evaporators are normally used for concentrating liquids having ___________________?
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A. Scaling characteristics

B. High viscosity

C. Both A. & B.

D. Neither A. nor B.

86. The equation, Nst = (f/2)/[1 + 5 (Npr 1) ?(f/2)], corresponds to ______________ analogy?
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A. Von-Karman

B. Prandtl

C. Colburn

D. Reynolds

87. The maximum heat transfer co-efficient from steam heating will be attained when the steam is_________________?
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A. Wet

B. None of these

C. Supersaturated

D. Saturated
88. Maximum heat transfer rate is obtained in ______________ flow?
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A. Creeping

B. Turbulent

C. Transition region

D. Laminar

89. A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when_________________?
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A. CPA > CPB

B. kA < 0.5 kB

C. CPA < CPB

D. kA >2 kB

90. In forced convection, the Nusselt number is a function of ____________________?
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A. Pr and Gr

B. Re and Pr

C. Re and Gr

D. Re and Sc

91. LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the ______________ flow?
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A. Parallel

B. Mixed

C. Same in either A , B. or C.

D. Counter flow

92. In Biot number, the characteristic length used is the ratio of the _______________ of the solid?
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A. Surface area to perimeter

B. Volume to surface area

C. Surface area to volume

D. Perimeter to surface area

93. In a gas-liquid shell and tube heat exchanger, the_________________?
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A. All A, B. & C.

B. Gases under high pressure are routed through the tube side, because high pressure gases are

C. rosive in nature

D. Presence of a non-condensable gas decreases the condensing film co-efficient

E. Gases to be heated/cooled is normally routed through the shell side, because the corrosion

F. sed by the cooling water or steam condensate remain localised to the tubes

94. The actual temperature drop across the heating surface of an evaporator depends on the_______________?
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A. Pressure difference between the steam chest and the vapor space above the boiling liquid

B. Liquid depth over the heating surface

C. Solution being evaporated

D. All A., B. and C.
95. Duhrings plot is of use in_________________?
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A. Extractive distillation

B. Leaching

C. Absorption

D. Evaporation
96. For what value of Prandtl number, St = f/2 ?
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A. < 1

B. 1

C. > 1

D. 1.5

97. For _______________ Prandtl number values, the heat conduction will be negligible in the buffer zone?
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A. No

B. Low

C. Extremely low

D. High
98. It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is___________________?
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A. < 0.50

B. > 0.75

C. < 0.75

D. < 0.25

99. Nusselt number is a function of Prandtl number and ______________ number of fluid in natural convection heat transfer?
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A. Reynolds

B. Biot

C. Stanton

D. Grashoff
100. Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?
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A. Between two bodies in physical contact with each other

B. Between two bodies not in physical contact with each other

C. From one part of a body to the another part of the same body

D. Both B & C