2. A dimensionless number which is the ratio of mass heat flow rate to the heat flow rate by conduction under a unit temperature gradient and through a thickness L is known as
Correct : E. Peclet number
3. The surface temperatures of a flat wall are 650?C and 450?C respectively and the thermal conductivity of the wall material is 0.30 kcal/m-hr-?C. The heat flux for a wall of 20 cm thickness will be
Correct : D. 300 kcal/m2-hr
4. Which of the following is a minimum boiling azeotrope?
Correct : E. Carbon disulphide-acetone
5. In a psychrometric chart the abscissa represents
Correct : D. Dry bulb temperature
6. For handling severely scaling liquids which of the following evaporator will be preferred?
Correct : A. Horizontal tube type
7. The factor which affects nucleate pool boiling is
Correct : E. All of the above
8. If the amount of radiant energy received per unit area per second from the sun is measured at the Earth, Mars and Jupiter it will be
Correct : B. in the increasing order - Jupiter, Mars, Earth
9. Two bodies one hot and the other cold are kept in vacuum. What will happen to the temperature of the hot body after sometime?
Correct : E. Decreases due to radiation
10. Transformer oil having kinematic viscosity of 3.66 x 10-6 m2/s flows through a tube 8 mm diameter at velocity of 0.6 m/s. The value of Reynolds number of flow would be
Correct : D. 1310
11. The thermal conductivity of wood depends upon
Correct : D. All of the above
12. In case of natural covection, the Nusselt number is function of
Correct : C. Grashof's number and Prandtl number
13. Transient heat flow occurs in
Correct : B. Heating and cooling of buildings due to sun
14. If thermal conductivity of aluminium is say 100 units at 0?C, the thermal conductivity at 500?C will be closer to
Correct : D. 140 units
15. The highest value of thermal conductivity is expected for
Correct : A. Solid ice
16. If the roof of a house is painted with a shiny metallic paint, the temperature inside will
Correct : B. Fall
17. Plank's law of radiation is applicable to
Correct : C. Monochromatic radiation
18. Diffusion coefficient of water into air at 26?C is nearly
Correct : E. 0.26 cm2/s
19. A wall has two layers A and B, each made of a different material. Both the layers have the same thickness. The thermal conductivity of material of A is twice that of B. Under the thermal equilibrium the temperature difference across the wall is 30?C. The temperature drops in layers A and B will be respectively
Correct : E. 20?C and 10?C
20. Hydrogen cannot be liquefied at room temperature because
Correct : B. its critical temperature is less than the room temperature
21. Ablation heat transfer method is used on
Correct : D. satellites
22. In case of a body transparent to thermal radiation
Correct : E. absorptivity = reflectivity = 0
23. The phenomenon of boiling the milk in an open container when milk spills over the vessel is termed as
Correct : A. Film boiling
24. A hollow sphere with uniform interior temperature and a small hole behaves very nearly as a
Correct : D. Black body
25. If a body reflects entire radiation incident on it, then it is known as
Correct : A. White body
26. Tea pots are highly polished
Correct : B. So that they may absorb all radiation from outside
27. A shpere, a cube and a disc all of the same material, quality and volume are heated to 900K and left in air. Which of these will have the lowest rate of cooling
Correct : A. Sphere
28. The overall co-efficient of heat transfer is expressed as
Correct : C. kcal/m2/hr/?C
29. The dimensions of specific heat are
Correct : B. LT-2?-1
30. A fur coat on an animal will help the animal to be
Correct : D. Warm in winter
31. The wagelength of X-rays is
Correct : A. 6 to 100000 micron
32. There are two spheres of copper the ratio of their radii being 1 : 3 both at the same temperature. The ration of heat contents will be
Correct : E. 1 ; 27
33. Which dimensionless number can be used for convective heat transfer?
Correct : E. Nusselt number
34. Essential requirement for the transfer of heat from one body to another is
Correct : C. Temperatures of the two bodies must be different
35. The ratio of specific heats of a gas is 1.4 and the value of specific heat at constant pressure is 7.0 cal/mole ?C. The difference between specific heat at constant presure and specific heat at constant volume will be
Correct : E. 2
36. The reflectance of a black body is
Correct : E. zero
37. A dimensionless heat transfer coefficient which gives a measure of the ratio of the heat transfer rate to the rate at which heat would be conducted within the fluid under a temperature gradient is known as
Correct : C. Nusselt number
38. If thermal conductivity of a material of wall varies as ko (1 - ?t ). The temperature at the centre of the wall will be
Correct : C. Less than that in case of constant thermal conductivity
39. Dynamic similarity is the similarity of
Correct : B. Forces
40. Which of the following is an example of absorption?
Correct : D. Removal of moisture from gasoline
41. The sensible heat of hot industrial gases can be recovered by a
Correct : C. Either of (A) and (B) above
42. For glass wool the thermal conductivity varies from sample to sample because of variations in
Correct : E. All of the above
43. Metals are good conductors of heat because
Correct : A. They contain free electrons
44. Which one of the following cannot be unit of thermal conductivity?
Correct : E. Watt / m2 K
45. A body cools from 80?C to 70?C in 10 minutes. The time taken by the body for further cooling to 60?C will be
Correct : D. More than 10 minutes
46. Calorific value of Indian coal is
Correct : D. 3300 kcal/kg
47. The statement that the emissivity and absorptivity of a surface is surrounded by its own temperature are the same for both monochromatic and total radiation, is known as
Correct : A. Kirchhoff's law
48. Emissivity and absorptivity of a surface are equal for radiation
Correct : D. with equal temperature and wavelength
49. The equation ?m x T = constant represents
Correct : A. Wein's Law
50. The face temperatures of a flat wall are 650?C and 450?C respectively and the thermal conductivity of wall material is 0.30 kcal/m-hr-?C. For a wall thickness of 20 cm, the rate of heat conduction per square meter of wall area will be
Correct : B. 300 kcal/hr
51. Pipes are insulated so that
Correct : B. Heat loss from the surface is minimized
52. The value of Stefan Boltzmann's constant in kcal-m2-hr-k4 is
Correct : C. 4.87 x 10-8
53. An isotherm is a graph
Correct : A. Showing pressure volume changes at constant temperature
54. A non-dimensional number which generally finds application in mass transfer problems is
Correct : A. Stanton number
55. The mass of water vapour per kg of the pressure of saturated vapour at the air is known as
Correct : A. Specific humidity
56. Unsaturated vapours
Correct : A. Do not obey gas laws
57. Four balls made of lead, glass, brass and iron made of same size, are heated to 100?C. They are simultaneously placed on a sheet of paraffin nearly 5 mm thick. Which ball will drop first?
Correct : D. Iron
58. Kinematic viscosity indicates
Correct : E. momentum transport by molecular friction
59. A piece of metal with a circular hole is heated. If the metal expands on heating the diameter of the hole will
Correct : A. Increase
60. Four rods with different radii 'r' and length 'l' are used to connect to reservoirs of heat at different temperature. Which one of them with conduct most heat?
Correct : B. r = 2 cm, l =
61. Which type of heat exchanger an automobile radiator is?
Correct : C. Cross flow type
62. The wavelength for maximum emissive power is given by
Correct : B. Wein's law
63. The emissivity of a body will be equal to absorptivity when
Correct : A. Body is in thermal equilibrium
64. In constant volume Hydrogen gas Thermometer, a correction has to be applied, because
Correct : B. Expansion of Hydrogen is non-linear
65. All substances emit radiation, the quality and quantity depending upon the absolute temperature and the properties of the material composing the radiating body. The above statement is known as the statement of
Correct : C. Planck's law
66. The unit of thermal conductivity in M.K.S. unit is
Correct : C. kcal/m2/?C sec
67. Radiation heats transfer between two surfaces can be reduced by
Correct : B. Introducing radiation shield between the surfaces
68. Thermal diffusivity is
Correct : E. A physical property of the material
69. In a thermal power plant, cooling towers are used to cool
Correct : C. circulating
70. A steam pipe is to be insulated by two insulating materials put over each other. For best results
Correct : A. Better matt. Over pipe and inferior over it
71. The rate of heat flow from a 50 mm thick wall of material having thermal conductivity of 40 W/m?C for a temperature difference of 10?C will be
Correct : E. 8000 W/m2 - hr
72. All temperatures above the freezing point of gold are usually determined by
Correct : C. Optical pyrometer
73. Two large closely spaced concentric spheres (both of which are perfect black body radiators) are maintained at temperatures of 127?C and 27?C respectively. The space in between the two spheres is evacuated. Taking Stefan Boltzmann constant as 5.67 x 108 watt m2K the rate of radiation in watts per sq. m between the two spheres is approximately
Correct : A. 992
74. A body cools from 90?C to 80?C in 5 minutes. Under the same external conditions to cool from 80?C to 70?C the body will take
Correct : D. More than 5 minutes
75. Maximum heat transfer rate can be expected in case of
Correct : A. Turbulent flow
76. Which liquid metal is supposed to be the best conductor
Correct : E. Sodium
77. In sugar mills cane juice is evaporated in
Correct : A. Long vertical tube evaporators
78. The unit of thermal diffusivity is
Correct : B. m2/hr
79. The diathermous body is one that
Correct : B. allows all the incident radiation to pass through it
80. Thermal conductivity of water at 20?C is nearly
Correct : E. 0.5
81. Dropwise condensation occurs on a
Correct : C. Oily surface
82. The value of reheat factor is of the order of
Correct : C. 1.02 to 1.06
83. Heat is transferred by conduction, convection and radiation in
Correct : C. Boiler furnaces
84. Which one of the following materials will have highest value of thermal conductivity?
Correct : A. Copper
85. In the temperature of air above a pond is 8?C thermal conductivity of ice is 0.005 C.G.S. units, latent heat of fusion of ice is 79.9 cal/gram the density of ice is 1 gm/cu.m, the time taken for the formation of ice layer of 1 cm thickness is
Correct : C. 12.5 seconds
86. The value of Prandtl number for air is of the order of
Correct : C. 0.7
87. The temperature reading taken using Centigrade and Fahrenheit thermometers are plotted on a graph -?C along X-axis, ?F along Y-axis. The shape of graph would be
Correct : E. Straight line cutting an intercept on the positive X-axis
88. Agitated film evaporator is suitable for concentrating
Correct : C. Viscous liquids
89. Hygrometer is used to measure
Correct : D. Relative humidity
90. a micron is equal to
Correct : A. 10-6 metres
91. The process of heat transfer during the re-entry of satellites and missiles, at very high speeds, into the earth's atmosphere is known as
Correct : D. Ablation
92. A slab of ice has one-half covered with black cloth and the other half with white cloth. The slab is now placed in sunlight. It will be observed that
Correct : B. more ice will melt under black cloth
93. In which of the following will the evaporation rate be large?
Correct : B. Near the mountain
94. A body which transmits all the radiations falling on it is known as
Correct : C. Transparent body
95. The value of the wavelength for maximum emissive power is given by
Correct : B. Wein's law
96. The material preferred for the fabrication of fruit juice concentrator is
Correct : D. Stainless steel sheet
97. Gases have poor
Correct : C. Reflectivity
98. Which is not the assumption in Fourier's equation of heat conduction?
Correct : A. Uniform area of cross-section
99. Unsteady state of heat flow occurs in
Correct : C. Annealing of castings
100. Which of the following has higher thermal conductivity as compared to the remaining?