MCQOPTIONS
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MCQOPTIONS
This section includes 153 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor) |
| A. | 2f |
| B. | f |
| C. | f/2 |
| D. | f/4 |
| Answer» D. f/4 | |
| 52. |
Convective heat transfer, in which heat is transferred by movement of warmed matter is described by |
| A. | Fourier's law |
| B. | Newton's law of cooling |
| C. | Fick's law |
| D. | None of these |
| Answer» C. Fick's law | |
| 53. |
In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid. |
| A. | Nucleate |
| B. | Pool |
| C. | Low pressure |
| D. | None of these |
| Answer» C. Low pressure | |
| 54. |
Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because |
| A. | Convection becomes important |
| B. | Conduction becomes important |
| C. | Radiation becomes important |
| D. | Sub-cooled boiling occurs |
| Answer» D. Sub-cooled boiling occurs | |
| 55. |
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 |
| A. | More |
| B. | Less |
| C. | Some |
| D. | Either more or less; depends on the nature of vapor |
| Answer» D. Either more or less; depends on the nature of vapor | |
| 56. |
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 |
| A. | U1 = U2 |
| B. | U2 > U1 |
| C. | U1 > U2 |
| D. | U1 = dirt factor - U2 |
| Answer» B. U2 > U1 | |
| 57. |
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by |
| A. | Painting the surface black |
| B. | Painting the surface white (with aluminium paint) |
| C. | Giving the surface a mirror finish |
| D. | Roughening the surface |
| Answer» C. Giving the surface a mirror finish | |
| 58. |
The energy distribution of an ideal reflector at higher temperatures is largely in the range of |
| A. | shorter wavelength |
| B. | longer wavelength |
| C. | remains same at all wavelengths |
| D. | wavelength has nothing to do with it |
| E. | none of the above. |
| Answer» B. longer wavelength | |
| 59. |
For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally |
| A. | Decreases |
| B. | Increases |
| C. | Remains unchanged |
| D. | Increases exponentially |
| Answer» B. Increases | |
| 60. |
For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then |
| A. | hf = hd |
| B. | hf > hd |
| C. | hf < hd |
| D. | hf could be greater or smaller than hd |
| Answer» D. hf could be greater or smaller than hd | |
| 61. |
According to Stefan s law, the total radiation from a black body per second per unit area is proportional to |
| A. | absolute temperature |
| B. | T2 |
| C. | T5 |
| D. | t |
| E. | l/T. |
| Answer» E. l/T. | |
| 62. |
The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit |
| A. | temperature |
| B. | thickness |
| C. | area |
| D. | time |
| E. | area and time. |
| Answer» E. area and time. | |
| 63. |
If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor. |
| A. | Increase |
| B. | Decrease |
| C. | Not affect |
| D. | Increase the condensing film co-efficient as well as |
| Answer» C. Not affect | |
| 64. |
Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid? |
| A. | Bleed point |
| B. | Vent |
| C. | Catchall |
| D. | Baffle |
| Answer» D. Baffle | |
| 65. |
Removal of __________ heat is involved in the condensation of a vapor under saturated conditions. |
| A. | Super |
| B. | Sensible |
| C. | Latent |
| D. | Both (B) & (C) |
| Answer» C. Latent | |
| 66. |
The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2 . The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 10-8 W/m2 .K4 ) |
| A. | 1000 |
| B. | 727 |
| C. | 800 |
| D. | 1200 |
| Answer» B. 727 | |
| 67. |
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) |
| A. | K/h0 |
| B. | 2K/h0 |
| C. | h0/K |
| D. | h0/2K |
| Answer» C. h0/K | |
| 68. |
Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by |
| A. | Eddies current |
| B. | Conduction |
| C. | Convection |
| D. | None of these |
| Answer» C. Convection | |
| 69. |
The concept of overall coefficient of heat transfer is used in heat transfer problems of |
| A. | conduction |
| B. | convection |
| C. | radiation |
| D. | all the three combined |
| E. | conduction and comte_ction. |
| Answer» F. | |
| 70. |
For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, t = excess temperature) |
| A. | t |
| B. | t2 |
| C. | t3 |
| D. | ( t) |
| Answer» B. t2 | |
| 71. |
1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass of moisture removed in kg is |
| A. | 520 |
| B. | 200 |
| C. | 400 |
| D. | 500 |
| Answer» D. 500 | |
| 72. |
According to Wien s law, the wavelength corresponding to maximum energy is proportion to |
| A. | absolute temperature (T) |
| B. | I2 |
| C. | f |
| D. | t |
| E. | 1/r. |
| Answer» B. I2 | |
| 73. |
A steam pipe is to be insulated by two insulating materials put over each other. For best results |
| A. | better insulation should be put over pipe and better one over it |
| B. | inferior insulation should be put over pipe and better one over it |
| C. | both may be put in any order |
| D. | whether to put inferior OIL over pipe or the better one would depend on steam temperature |
| E. | unpredictable. |
| Answer» B. inferior insulation should be put over pipe and better one over it | |
| 74. |
At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below: The thermal conductivity of material I |
| A. | Is smaller than that of II |
| B. | Is greater than that of II |
| C. | Is equal to that of II |
| D. | Can be greater than or smaller than that of II |
| Answer» B. Is greater than that of II | |
| 75. |
Which of the following is the most widely used heat insulating material for pipelines carrying steam? |
| A. | Tar dolomite bricks followed by asbestos |
| B. | Fireclay refractory followed by aluminium sheet |
| C. | Cotton followed by aluminium foil |
| D. | 85% magnesia cement and glass wool |
| Answer» E. | |
| 76. |
Electro-magnetic spectrum range, which is important for radiation varies from __________ microns. |
| A. | 1 to 100 |
| B. | 0.5 to 50 |
| C. | 10 to 100 |
| D. | 100 to 1000 |
| Answer» C. 10 to 100 | |
| 77. |
Heat transfer occurs by natural convection because change in temperature causes difference in |
| A. | Viscosity |
| B. | Density |
| C. | Thermal conductivity |
| D. | Heat capacity |
| Answer» C. Thermal conductivity | |
| 78. |
At constant temperature, the thermal conductivities of gases __________ with rise in pressure. |
| A. | Decrease |
| B. | Increase |
| C. | Remain unchanged |
| D. | May increase or decrease; depends on the pressure |
| Answer» B. Increase | |
| 79. |
In heat exchangers, degree of approach is defined as the difference between temperatures of |
| A. | cold water inlet and outlet |
| B. | hot medium inlet and outlet |
| C. | hot medium outlet and cold water inlet |
| D. | hot medium outlet and cold water outlet |
| E. | none of the above. |
| Answer» E. none of the above. | |
| 80. |
Thermal conductivity of glass-wool varies from sample to sample because of variation in |
| A. | composition |
| B. | density |
| C. | porosity |
| D. | structure |
| E. | all of the above. |
| Answer» F. | |
| 81. |
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube |
| A. | Exit-fluid temperature > wall temperature |
| B. | Exit fluid temperature < wall temperature |
| C. | Exit fluid temperature = wall temperature |
| D. | Graetz number > 100 |
| Answer» D. Graetz number > 100 | |
| 82. |
A non-dimensional number generally associated with natural convection heat transfer is |
| A. | Grashoff number |
| B. | Nusselt number |
| C. | Weber number |
| D. | Prandtl number |
| E. | Reynold number. |
| Answer» B. Nusselt number | |
| 83. |
Moisture would find its way into insulation by vapour pressure unless it is prevented by |
| A. | high thickness of insulation |
| B. | high vapour pressure |
| C. | less thermal conductivity insulator |
| D. | a vapour seal |
| E. | all of the above. |
| Answer» E. all of the above. | |
| 84. |
The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns. |
| A. | 0.38-0.78 |
| B. | 0.5-50 |
| C. | 100-1000 |
| D. | 5-50 |
| Answer» C. 100-1000 | |
| 85. |
Evaporation of 1kg of water from a solution in a single effect evaporator requires about __________ kg of steam. |
| A. | 0.4 - 0.6 |
| B. | 1-1.3 |
| C. | 1.8-2 |
| D. | 2 - 2.4 |
| Answer» C. 1.8-2 | |
| 86. |
For evaporation of viscous solution in a multiple effect evaporator, the preferred feeding scheme is |
| A. | Forward |
| B. | Backward |
| C. | Parallel |
| D. | None of these |
| Answer» C. Parallel | |
| 87. |
Electromagnetic radiations propagate in vacuum with a velocity of __________ metre/second. |
| A. | 3 105 |
| B. | 3 108 |
| C. | 3 1010 |
| D. | 3 1012 |
| Answer» C. 3 1010 | |
| 88. |
Indirect contact heat exchangers are preferred over direct contact heat exchangers, because |
| A. | Heat transfer co-efficient are high |
| B. | There is no risk of contamination |
| C. | There is no mist formation |
| D. | Cost of equipment is lower |
| Answer» C. There is no mist formation | |
| 89. |
The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation. |
| A. | Increases |
| B. | Decreases |
| C. | Remain constant |
| D. | May increase or decrease; depends on the material |
| Answer» E. | |
| 90. |
Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in |
| A. | electric heater |
| B. | steam condenser |
| C. | melting of ice |
| D. | refrigerator condenser coils |
| E. | boiler. |
| Answer» F. | |
| 91. |
The statement that "maximum wavelength of radiation is inversely proportional to the temperature" is __________ law. |
| A. | Stefan-Boltzmann s |
| B. | Planck's |
| C. | Wien's displacement |
| D. | None of these |
| Answer» D. None of these | |
| 92. |
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) |
| A. | K/h0 |
| B. | 2K/h0 |
| C. | hi/K |
| D. | 2hi/K |
| Answer» B. 2K/h0 | |
| 93. |
A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300 C and allowed to cool in natural air. Which one will cool the slowest? |
| A. | Cube |
| B. | Plate |
| C. | Sphere |
| D. | All will cool at the same rate |
| Answer» D. All will cool at the same rate | |
| 94. |
For a given ambient air temperature with increase in the thickness of insulation of a hot cylindrical pipe, the rate of heat loss from the surface would |
| A. | Decrease |
| B. | Increase |
| C. | First decrease and then increase |
| D. | First increase and then decrease |
| Answer» E. | |
| 95. |
If the temperature of a solid surface changes form 27 C to 627 C, then its emissive power changes in the ratio of |
| A. | 3 |
| B. | 6 |
| C. | 9 |
| D. | 27 |
| E. | 81. |
| Answer» F. | |
| 96. |
The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoff s law. |
| A. | Wavelength of radiation |
| B. | Nature of the body |
| C. | Temperature of the body |
| D. | None of these |
| Answer» D. None of these | |
| 97. |
Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface? |
| A. | Liquid density |
| B. | Liquid viscosity |
| C. | Hot surface temperature |
| D. | Interfacial tension |
| Answer» E. | |
| 98. |
The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is |
| A. | 1.66 |
| B. | 88.66 |
| C. | 3.66 |
| D. | Dependent on NRe only |
| Answer» D. Dependent on NRe only | |
| 99. |
Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called |
| A. | thermal resistance |
| B. | thermal coefficient |
| C. | temperature gradient |
| D. | thermal conductivity |
| E. | heat-transfer. |
| Answer» E. heat-transfer. | |
| 100. |
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 |
| A. | Less corrosion problems |
| B. | Flexibility possible in the baffle arrangement |
| C. | Low pressure drop |
| D. | High heat transfer co-efficient |
| Answer» C. Low pressure drop | |