1. Boiling point elevation for a strong and concentrated solution is found by Duhring's rule,
which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water.
Correct : A. Boiling point
2. In case of heat flow by conduction for a cylindrical body with an internal heat source, the
nature of temperature distribution is
Correct : C. Parabolic
3. The average heat transfer co-efficient over the entire length of the plate (ha) and the local
heat transfer co-efficient (hL), in case of heat transfer over a flat plate in laminar zone is related as
Correct : B. ha = 2hL
4. Which has the lowest Prandtl number?
Correct : A. Liquid metal
5. Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K)
Correct : B. T4
6. The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat
exchanger is
Correct : D. 1/4
7. The equation, (NSt × N 2/3 Pr) = f/2, is the __________ analogy.
Correct : A. Colburn
8. What is the geometric mean of two heat transfer areas A1 and A2?
Correct : A. √(A1 . A2)
9. The range of electromagnetic spectrum important in heat transfer by radiation is
__________ microns.
Correct : B. 0.5-50
10. Stefan's block body radiation law can also be derived from __________ law.
Correct : B. Planck's
11. Boiling point of a solution according to Duhring's rule is a linear function of the
__________ of water.
Correct : A. Boiling point (at the same pressure)
12. Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around
__________ BTU.
Correct : A. 180
13. Prandtl number for most of dry gases is about
Correct : B. 0.72
14. Pick out the wrong statement.
Correct : A. The emissivity of a surface decreases, if it gets corroded by atmospheric environment
15. 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
Correct : B. Flexibility possible in the baffle arrangement
16. Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is
Correct : D. 0.7
17. The purpose of providing expansion bellows in the shell of tubular exchanger is to
Correct : C. Account for the uneven expansion of shell and tube bundles
18. An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a
Correct : B. Heat exchanger
19. Multipass heat exchangers are used
Correct : C. To obtain higher heat transfer co-efficient and shorter tube
20. A black body does not __________ radiation.
Correct : D. Both (B) & (C)
21. 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
Correct : B. < 0.75
22. Multiple effect evaporation accounts for
Correct : A. Steam economy
23. Finned tube heat exchangers
Correct : A. Give larger area per tube
24. Tube expansion allowances exist in __________ heat exchanger.
Correct : B. U-tube
25. Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.
Correct : B. Falling film
26. Pick out the wrong statement.
Correct : B. The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1. If the surface temperature is halved, the maximum in the emissive power would occur at a wavelength of 0.5 λ1
27. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as
Correct : B. D-0.2
28. Minimum recommended baffle spacing in a shell and tube heat exchanger is about
(where, D = shell diameter).
Correct : A. 0.2 D
29. For heat flow through very thick walled cylinder, use _________mean radius.
Correct : B. Logarithmic
30. Corrosiveness of steam condensate is due to the presence of
Correct : C. Both (A) & (B)
31. In a shell and tube heat exchanger, the shell side fluid velocity can‟t be changed by
changing the
Correct : B. Tube diameter
32. Solid angle subtended by the finite surface at the radiating element is
Correct : B. Called the angle of vision
33. 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.
Correct : D. Same in either 'a', b' or 'c'
34. A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for
radiative heat transfer of the outer sphere with respect to the inner sphere is
Correct : B. R2/(R1+R2)
35. The maximum heat transfer co-efficient from steam heating will be attained when the
steam is:
Correct : B. Saturated
36. One kilogram of water at 0°C is changed to superheated steam of one atm pressure and
300° C. The major heat consumption in the process will be to
Correct : B. Evaporate the water
37. The film co-efficient is decreased due to the presence of non-condensing gases in the vapors.
The film co-efficient of superheated vapor as compared to that of saturated vapor is
Correct : C. Some
38. The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe
in laminar flow are
Correct : D. Nu, Gz
39. Which of the following has maximum thermal conductivity?
Correct : A. Iron
40. In case of heat transfer by conduction in a hollow cylinder, __________ mean area is used
to calculate the heat transfer rate.
Correct : C. Logarithmic
41. The absorptivity of a grey body at a given temperature __________ with increasing
wavelength of radiation.
Correct : D. May increase or decrease; depends on the material
42. Thermal diffusivity of a material
Correct : D. All (A), (B) and (C)
43. Forced circulation evaporators are useful for the concentration of viscous, salting and scale
forming liquors. Which of the following is a forced circulation evaporator?
Correct : C. Agitated film evaporator
44. Nusselt number is the ratio of the temperature gradient at the wall to
Correct : C. That across the entire pipe
45. Which of the following has the lowest overall heat transfer co-efficient?
Correct : D. Air
46. What is the unit of thermal conductivity?
Correct : B. Kcal/hr.m.°C
47. Indirect contact heat exchangers are preferred over direct contact heat exchangers,
because
Correct : B. There is no risk of contamination
48. Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping
Correct : A. Both the tube sheets fixed
49. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe
is negligible, if the value of Prandtl number is
Correct : C. 0.6
50. What is the emissivity of a black body?
Correct : B. 1
51. The actual temperature drop across the heating surface of an evaporator depends on the
Correct : D. All (A), (B) and (C)
52. In SI units, thermal conductivity is expressed in
Correct : A. Watt/m.°K
53. jH factor for heat transfer depends upon the __________ number.
Correct : C. Reynolds
54. In pipe flow, heat is transferred from hot wall to the liquid by
Correct : C. Forced convection and conduction
55. A perfect black body is a perfect __________ of radiation.
Correct : C. Both (A) & (B)
56. Heat transfer rate described by Fourier's law will decrease, if the __________ increases.
Correct : B. Thickness
57. The absorptivity of a body is equal to its emissivity
Correct : C. Under thermal equilibrium
58. In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will
Correct : C. Remain unchanged
59. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is
Correct : A. 165.4
60. Which one gives the monochromatic emissive power for black body radiation?
Correct : A. Planck's law
61. If heat transfer rate varies with the time, it is termed as
Correct : D. None of these
62. Absorptivity and reflectivity of a perfect black body are respectively
Correct : A. 1 and 0
63. __________ heat exchanger is used for chilling oil to be dewaxed.
Correct : B. Double pipe
64. Pick out the correct equation.
Correct : A. jH = (St)(Pr) 2/3 = f/2
65. It is not preferable to use superheated steam in evaporators, because of its very
Correct : C. Low film co-efficient
66. Water is normally used as a coolant in the heat exchange equipments mainly because of its
Correct : A. Abundance & high heat capacity
67. A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of
Correct : B. 2 0.8
68. At constant temperature, the thermal conductivities of gases __________ with rise in
pressure.
Correct : A. Decrease
69. Stefan-Boltzmann law applies to __________ body.
Correct : A. Black
70. When warm and cold liquids are mixed, the heat transfer is mainly by
Correct : B. Convection
71. A BTU/hr.ft.2 °F is equal to
Correct : B. 4.88 kcal/hr. m.2 °C
72. Open pan evaporators are preferred to be used, when the solution to be concentrated is
Correct : B. Highly viscous
73. A __________ evaporator employs an annular downtake.
Correct : A. Basket type
74. The equation, Nst = (f/2)/[1 + 5 (Npr - 1) √(f/2)], corresponds to __________ analogy.
Correct : D. Prandtl
75. The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat
exchanger is
Correct : C. Higher tube side heat transfer co-efficient
76. With increase in temperature, the thermal conductivity of fresh lubricating oil
Correct : B. Decreases
77. Vent pipes are provided in a condenser to
Correct : A. Remove non-condensable gases
78. To reduce the tube side pressure drop for the same flow rate, the heat exchanger
recommended is
Correct : B. 1-1 heat exchanger
79. LMTD for counter-flow and parallel flow heat exchanger will be the same, when the
Correct : A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)
80. In case of __________ boiling, the liquid temperature is below the saturation temperature
and the boiling takes place in the vicinity of the heated surface.
Correct : B. Local
81. Steam trap is used to
Correct : B. Remove water resulting from partial condensation of steam
82. For __________ Prandtl number values, the heat conduction will be negligible in the buffer
zone.
Correct : C. High
83. Planck's distribution law is valid for __________ bodies.
Correct : C. Coloured
84. Electro-magnetic spectrum range, which is important for radiation varies from __________
microns.
Correct : B. 0.5 to 50
85. In a shell and tube heat exchanger, square pitch compared to triangular pitch
Correct : A. Gives a higher shell side pressure drop
86. A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C
in __________ minutes.
Correct : B. > 10
87. In a gas-liquid shell and tube heat exchanger, the
Correct : D. All 'a', 'b' & 'c'
88. For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it
Correct : D. All (A), (B) and (C)
89. Terminal point temperature differences between fluids in case of a heat exchanger is termed as
Correct : A. Approach
90. The Stefan-Boltzmann constant depends on the
Correct : D. None of these
91. 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
Correct : C. kA < 0.5 kB
92. In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used
Correct : B. In high range of temperature differences
93. Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt
deposited on either side has coefficient U2, then
Correct : A. U1 = U2
94. In forced convection, the Nusselt number is a function of
Correct : A. Re and Pr
95. Maximum heat transfer rate is achieved in __________ flow.
Correct : C. Turbulent
96. Radiator of an automobile engine is a __________ type of heat exchanger.
Correct : D. Direct contact
97. Temperature profile in steady state heat transfer is
Correct : D. Linear
98. Which of the following parameters is increased by use of finned tube in a multipass shell
and tube heat exchanger?
Correct : D. All (A) (B) and (C)
99. A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is __________ °C.
Correct : B. 12
100. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet
or a spherical particle to a surrounding stagnant film is