MCQOPTIONS
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MCQOPTIONS
This section includes 253 Mcqs, each offering curated multiple-choice questions to sharpen your Heat Transfer (HT) knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Which variety of steel may be expected to have lowest value of thermal conductivity? |
| A. | High carbon steel (0.83% C) |
| B. | Low nickel steel (1.37% Ni) |
| C. | Low chromium steel (0.46% Cr) |
| D. | High chromium steel (0.26% Cr) |
| E. | Chromium nickel steel (9% Ni, 18% Cr) |
| Answer» F. | |
| 52. |
Entrainment separator is used in evaporators to |
| A. | Reduce the boiling point |
| B. | Increase the boiling point |
| C. | Separate liquid droplets from vapour |
| D. | Prevent foaming |
| E. | Discharge mud and other impurities |
| Answer» D. Prevent foaming | |
| 53. |
A sphere 15 cm in diameter is covered with 5 cm of insulation (k = 0.057 kcal/m-hr-?C). The inside and outside surface temperature of the insulation are 315?C and 80?C respectively. The heat loss per sq. m of the outside surface will be closer to |
| A. | 80 kcal/hr |
| B. | 320 kcal/hr |
| C. | 160 kcal/hr |
| D. | 37,500 kg |
| E. | 40 kcal/hr |
| Answer» D. 37,500 kg | |
| 54. |
Heat is transferred from an insulated pipe to the surrounding still air mainly by |
| A. | Free convection |
| B. | Forced convection |
| C. | All above together |
| D. | Radiation |
| E. | Conduction |
| Answer» B. Forced convection | |
| 55. |
Which one of the following will have least value of thermal conductivity? |
| A. | Silver |
| B. | Water |
| C. | Glass |
| D. | Air |
| E. | Copper |
| Answer» E. Copper | |
| 56. |
In which of the following heat exchange process, the value of overall heat transfer coefficient will be highest? |
| A. | Air to carbondioxide |
| B. | Air to heavy tars |
| C. | 37,500 kg |
| D. | Steam condensers |
| E. | Steam to oil |
| Answer» E. Steam to oil | |
| 57. |
The dimensions of thermal conductivity are |
| A. | MLT-3 ?-1 |
| B. | MLT?3 |
| C. | ML-1T2 ? |
| D. | MLT2 ?2 |
| E. | 37,500 kg |
| Answer» B. MLT?3 | |
| 58. |
Thermal conductivity of wood least depends on |
| A. | Moisture |
| B. | Density |
| C. | Temperature |
| D. | Grain orientation |
| E. | All of the above |
| Answer» E. All of the above | |
| 59. |
Dynamic similarity refers to the similarity of |
| A. | 37,500 kg |
| B. | temperature and heat flux |
| C. | masses and forces |
| D. | velocity and acceleration |
| E. | physical dimensions |
| Answer» F. | |
| 60. |
A grey body has emissivity |
| A. | 37,500 kg |
| B. | 1 |
| C. | less than 1 |
| D. | more than 1 |
| E. | 0.5 |
| Answer» D. more than 1 | |
| 61. |
A correction of LMTD is necessary in case of |
| A. | Parallel flow heat exchanger |
| B. | Counter current heat exchanger |
| C. | Cross flow heat exchanger |
| D. | All of the above |
| E. | None of the above |
| Answer» D. All of the above | |
| 62. |
In an air-conditioning plant a cooling tower is used to cool |
| A. | air |
| B. | refrigerant |
| C. | condenser water |
| D. | None of the above |
| E. | 37,500 kg |
| Answer» D. None of the above | |
| 63. |
If thermal conductivity of aluminium is say 100 units at 0?C, the thermal conductivity at 500?C will be closer to |
| A. | 37,500 kg |
| B. | 100 units |
| C. | 20 units |
| D. | 140 units |
| E. | 50 units |
| Answer» E. 50 units | |
| 64. |
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 |
| A. | 15?C and 15?C |
| B. | cannot be predicated |
| C. | 37,500 kg |
| D. | 10?C and 20?C |
| E. | 20?C and 10?C |
| Answer» F. | |
| 65. |
Transmission of heat by molecular collision is |
| A. | Scattering |
| B. | Transmission |
| C. | Radiation |
| D. | Convection |
| E. | Conduction |
| Answer» E. Conduction | |
| 66. |
Two rods one of copper and the other of mild steel, both of diameter 20 mm and length 250 mm are coated with a uniform layer of wax all around. These rods are placed vertically in a boiling water bath with 200 mm, length of each rod projecting outside. If the melting point of wax is 10?C, then |
| A. | equal quantity of wax will meet on the two rods |
| B. | more wax will melt on copper rod as compared to mild steel rod |
| C. | 37,500 kg |
| D. | nothing can be predioted as the data is insufficient |
| E. | more wax will melt on mild steel rod as compared to copper rod |
| Answer» C. 37,500 kg | |
| 67. |
A vapour containing liquid particles to the extent of 50% by the volume is known as |
| A. | Saturate vapour |
| B. | Superheated vapour |
| C. | Super saturated liwuid |
| D. | Wet vapour |
| E. | Saturated liquid |
| Answer» E. Saturated liquid | |
| 68. |
When metallic surfaces are oxidized the emissivity |
| A. | Depends on the temperature |
| B. | Depends on other factors |
| C. | Decreases |
| D. | Does not change |
| E. | Increases |
| Answer» F. | |
| 69. |
Which of the following is used as entrainer in acetic acid - water separation? |
| A. | Butyl acetate |
| B. | Methyl alcohol |
| C. | Benzene. |
| D. | Phosphorous |
| E. | Hexane |
| Answer» B. Methyl alcohol | |
| 70. |
The nature of flow of a fluid inside a tube i.e., whether it is turbulent or laminar, is ascertained by |
| A. | Viscosity of fluid |
| B. | Flow velocity |
| C. | Surface conditions |
| D. | Tube size |
| E. | Reynolds number |
| Answer» F. | |
| 71. |
The coefficient of linear expansion of a solid is L. The volume V of a cube of this solid on being heated by 1?C will change by |
| A. | VL |
| B. | VL/3 |
| C. | 3 VL |
| D. | 37,500 kg |
| E. | 3L |
| Answer» D. 37,500 kg | |
| 72. |
The lower temperature limit for mercury thermometer is |
| A. | Absolute zero |
| B. | 0?F |
| C. | ? 39?F |
| D. | 0?C |
| E. | 100?C |
| Answer» D. 0?C | |
| 73. |
Which of the following material has lest value of thermal diffusivity? |
| A. | Aluminium |
| B. | Rubber |
| C. | Lead |
| D. | Mercury |
| E. | Iron |
| Answer» C. Lead | |
| 74. |
Which of the following provides maximum contact surface for a liquid vapour system? |
| A. | Wetted wall column |
| B. | Packed tower |
| C. | Sieve plant column |
| D. | Benzene. |
| E. | Bubble cap tower |
| Answer» B. Packed tower | |
| 75. |
The total solar radiation incident on a body is 1000 kcal/min. The body reflects 400 kcal/min. If the transmissivity of the surface will be |
| A. | 0.85 |
| B. | 0.3 |
| C. | 0.45 |
| D. | 0.15 |
| E. | 0.4 |
| Answer» D. 0.15 | |
| 76. |
For a opaque body |
| A. | reflectivity = 0 |
| B. | absorptivity = reflectivity = 1 |
| C. | 37,500 kg |
| D. | absorptivity + reflectivity = 1 |
| E. | absorptivity = 0 |
| Answer» E. absorptivity = 0 | |
| 77. |
Ice is slippery when a man walks on it for |
| A. | There is no friction |
| B. | Increase of pressure causes it to melt |
| C. | It is very chill |
| D. | Its surface is smooth |
| E. | It has lubricating qualities |
| Answer» C. It is very chill | |
| 78. |
The average value of thermal conductivity for air at 20?C is about |
| A. | 0.11 |
| B. | 0.011 |
| C. | 0.022 |
| D. | None of the above |
| E. | Nichrome |
| Answer» D. None of the above | |
| 79. |
In which case the value of thermal conductivity drops with rising temperature |
| A. | Methane |
| B. | Benzene |
| C. | Carbondioxide |
| D. | Ammonia |
| E. | None of the above |
| Answer» F. | |
| 80. |
For which fluid combination the value of overall heat transfer coefficient will be least? |
| A. | Alcohol condensers |
| B. | Air to heavy tars |
| C. | Feed water heaters |
| D. | 37,500 kg |
| E. | Air condensers |
| Answer» C. Feed water heaters | |
| 81. |
Oxygen boils at -183?C, this temperature is |
| A. | ? 215?F |
| B. | ? 361?F |
| C. | ? 227?F |
| D. | ? 329?F |
| E. | ? 398?F |
| Answer» D. ? 329?F | |
| 82. |
Heat is transferred from an electric bulb mainly by |
| A. | Conduction, convection and radiation. |
| B. | Radiation |
| C. | Convection and conduction |
| D. | Convection |
| E. | Conduction |
| Answer» C. Convection and conduction | |
| 83. |
A dimensionless number which is the ratio of kinematic viscosity to thermal diffusivity is known as |
| A. | Grashoff number |
| B. | Reynolds number |
| C. | Prandtl number |
| D. | Pacelet number |
| E. | Nusselt number |
| Answer» D. Pacelet number | |
| 84. |
The emissive power of a body depends on |
| A. | Nature of body |
| B. | Temperature of body |
| C. | Physical nature |
| D. | All of the above |
| E. | None of the above |
| Answer» E. None of the above | |
| 85. |
In case the hydrodynamic and thermal boundary layers are identical for a fluid flowing over a heated plate |
| A. | The value of Prandtl number must be 0.5 |
| B. | The plate surface must be smooth |
| C. | The plate must be of low thermal conductivity |
| D. | The value of Prandtl number thust be 1 |
| E. | The value of Prandtl number must be zero |
| Answer» E. The value of Prandtl number must be zero | |
| 86. |
Which one of the following will radiate heat to a large extent? |
| A. | White polished surface |
| B. | White rough surface |
| C. | Black rough surface |
| D. | Black polished surface |
| E. | None of the above |
| Answer» B. White rough surface | |
| 87. |
DBA = DAB, in case of |
| A. | Stagnet diffusion |
| B. | Equimolar counter diffusion |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| E. | 2.6 cm2/sec |
| Answer» C. Either of (A) and (B) above | |
| 88. |
Which of the following has the highest value of the thermal conductivity |
| A. | Wood |
| B. | Asbestos |
| C. | Nichrome |
| D. | Clay |
| E. | Refractory brick |
| Answer» D. Clay | |
| 89. |
The transfer of heat in case of radiation takes place by means of |
| A. | Heated particles of the medium |
| B. | Electromagnetic waves |
| C. | Thermal energy of the source |
| D. | None of the above |
| E. | 37,500 kg |
| Answer» B. Electromagnetic waves | |
| 90. |
In a shell and tube heat exchanger, the corrosive liquid is normally passed through |
| A. | Shell side |
| B. | Tube side |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| E. | None of the above |
| Answer» C. Either of (A) and (B) above | |
| 91. |
Ditus Boelter equation is applicable in case of fluids flowing in |
| A. | Laminar region |
| B. | Turbulent region |
| C. | Transition region |
| D. | Any of the above |
| E. | None of the above |
| Answer» C. Transition region | |
| 92. |
In a cooling tower which mode of heat transfer plays insignificant role? |
| A. | Evaporative cooling |
| B. | Convective cooling |
| C. | Radiaion |
| D. | All of the above |
| E. | 37,500 kg |
| Answer» D. All of the above | |
| 93. |
Longest wavelength |
| A. | Ultraviolet rays |
| B. | Infrared rays |
| C. | Gamma rays |
| D. | X-rays |
| E. | Radio waves |
| Answer» D. X-rays | |
| 94. |
Which of the following is wrong |
| A. | Black surfaces are better absorbers than white ones |
| B. | Black surfaces are better radiators than white ones |
| C. | Rough surfaces are better radiators than smooth surfaces |
| D. | 37,500 kg |
| E. | Highly polished mirror like surfaces are very good radiators |
| Answer» F. | |
| 95. |
All bodies above absolute zero temperature emit radiation". Above statement is based on |
| A. | D'Alambert's rule |
| B. | Wein's law |
| C. | Stefan law |
| D. | Planck's law |
| E. | Prevost theory |
| Answer» F. | |
| 96. |
A high value of Prandtl number indicates |
| A. | rapid diffusion of momentum by viscous action compared to diffusion of energy |
| B. | relative heat transfer by conduction to convection |
| C. | rapid heat transfer by forced convection to natural convection |
| D. | None of the above |
| E. | 37,500 kg |
| Answer» B. relative heat transfer by conduction to convection | |
| 97. |
The radiation from flames consists of |
| A. | Continuous radiation from burning soot particles of microscopic and submicroscopic dimensions |
| B. | Radiation from suspended larger particles of coal, coke or ash contributing to flame luminosity |
| C. | Infrared radiation from water vapour and carboundioxide |
| D. | Non-equilibrium radiation associated with the combustion process |
| E. | All of the above |
| Answer» F. | |
| 98. |
Formation of fog is due to |
| A. | High pressure |
| B. | Humidity |
| C. | Temperature fall of atmosphere |
| D. | Low pressure |
| E. | Night showers |
| Answer» D. Low pressure | |
| 99. |
Which of the following are generally diathermanous? |
| A. | Solids |
| B. | Liquids |
| C. | Gases |
| D. | All of the above |
| E. | 37,500 kg |
| Answer» D. All of the above | |
| 100. |
Which dimensionless number indicates the relative strength of the buoyant to viscous forces? |
| A. | Froude's number |
| B. | 37,500 kg |
| C. | Prandtl number |
| D. | Weber number |
| E. | Grashoff number |
| Answer» D. Weber number | |