MCQOPTIONS
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MCQOPTIONS
This section includes 86 Mcqs, each offering curated multiple-choice questions to sharpen your Heat Transfer knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Adiabatic wall temperature is |
| A. | equal to stagnation temperature |
| B. | greater than stagnation temperature |
| C. | less than stagnation temperature |
| D. | the temperature of adiabatic surface |
| Answer» D. the temperature of adiabatic surface | |
| 52. |
\(\frac{{Nusselt~number}}{{Reynold's~number\;\times\;Prandtl~number }}\) = ? |
| A. | Weber number |
| B. | Stanton number |
| C. | Biot number |
| D. | Mach number |
| Answer» C. Biot number | |
| 53. |
Air at 20°C blows over a plate of 50 cm × 75 cm maintained at 250°C. If the convection heat transfer coefficient is 25 W/m2°C, the heat transfer rate is |
| A. | 2.156 kW |
| B. | 2156 kW |
| C. | 215.6 kW |
| D. | 21.56 kW |
| Answer» B. 2156 kW | |
| 54. |
Film coefficient is defined as |
| A. | \(\frac{{{\rm{Inside\;diameter\;of\;the\;tube}}}}{{{\rm{equivalent\;thickness\;of\;the\;film}}}}\) |
| B. | \(\frac{{{\rm{specific\;heat\;}} \times {\rm{\;viscosity}}}}{{{\rm{thermal\;conductivity}}}}\) |
| C. | \(\frac{{{\rm{thermal\;conductivity}}}}{{{\rm{equivalent\;thickness\;of\;the\;film}}}}\) |
| D. | \(\frac{{{\rm{molecular\;diffusivity\;or\;momentum}}}}{{{\rm{thermal\;diffusivity}}}}\) |
| Answer» D. \(\frac{{{\rm{molecular\;diffusivity\;or\;momentum}}}}{{{\rm{thermal\;diffusivity}}}}\) | |
| 55. |
Match the following:AStanton Number1Surface TensionBMach Number2Mass TransferCWeber Number3Forced ConvectionDSchmidt Number4Compressibility |
| A. | A-4, B-3, C-2, D-1 |
| B. | A-3, B-4, C-1, D-2 |
| C. | A-1, B-2, C-3, D-4 |
| D. | A-2, B-3, C-4, D-1 |
| Answer» C. A-1, B-2, C-3, D-4 | |
| 56. |
Grashof number signifies the ratio of |
| A. | inertia force to viscous force |
| B. | buoyancy force to viscous force |
| C. | buoyancy force to inertia force |
| D. | inertia force to surface tension force |
| Answer» C. buoyancy force to inertia force | |
| 57. |
A flat plate of length 1 m and width 50 cm is placed in an air stream at 30°C blowing parallel to it. The convective heat transfer coefficient is 30 W/(m2K). The heat transfer if the plate is maintained at a temperature of 400°C is |
| A. | 5.55 kW |
| B. | 4.05 kW |
| C. | 55.5 kW |
| D. | 6 kW |
| Answer» B. 4.05 kW | |
| 58. |
Consider the following statements:1. In natural convection turbulent flow over heated vertical plate, h is independent of the characteristic length.2. In turbulent flow, non-dimensional heat transfer coefficient for natural convection over a heated vertical plate is given by\(Nu = c{\left( {Pr} \right)^{1/3}}\)Which of the above statements /are correct? |
| A. | 1 only |
| B. | Both 1 and 2 |
| C. | 2 only |
| D. | Neither 1 nor 2 |
| Answer» C. 2 only | |
| 59. |
A flat plate has thickness 5 cm, thermal conductivity 1 W/mK, convective heat transfer coefficients on its two flat faces of 10 W/m2K and 20 W/m2K. The overall heat transfer coefficient for such a flat plate is |
| A. | 5 W/m2K |
| B. | 6.33 W/m2K |
| C. | 20 W/m2K |
| D. | 30 W/m2K |
| Answer» B. 6.33 W/m2K | |
| 60. |
Air at 293 K is flowing with a velocity of 3 m/s over a heated flat square plate. Plate is 0.3 m wide and is maintained at 330 K. Average heat loss from the plate due to convection is (Take v = 16.768E-6 m2/s, Pr = 0.7, k = 0.027 W/m K) |
| A. | 22 W |
| B. | 37 W |
| C. | 45 W |
| D. | 41 W |
| Answer» E. | |
| 61. |
A coolant fluid at 30°C flows over a heated flat plate maintained at a constant temperature of 100°C. The boundary layer temp distribution at a given location on the plate may be approximated as T = 30 + 70exp(-y), where y (in m) is the distance normal to the plate and T is in °C. If the thermal conductivity of the fluid is 1.0 W/mK, the local convective heat transfer (in W/m2K) at that location will be |
| A. | 0.2 |
| B. | 1 |
| C. | 5 |
| D. | 10 |
| Answer» C. 5 | |
| 62. |
Convective heat transfer coefficient is a function of: |
| A. | Nature of the fluid flow only |
| B. | Properties of fluid only |
| C. | Configuration of body only |
| D. | Nature of the fluid flow, properties of fluid and configuration of body |
| Answer» E. | |
| 63. |
For flow of fluid over a heated plate, the following fluid properties are known viscosity = 0.001 Pa.s ; specific heat at constant pressure = 1 kJ/kg.K ; thermal conductivity = 1 W/m.k. The hydrodynamic boundary layer thickness at a specified location on the plate is 1 mm. The thermal boundary layer thickness at the same location is |
| A. | 0.001 mm |
| B. | 0.01 mm |
| C. | 1 mm |
| D. | 1000 mm |
| Answer» D. 1000 mm | |
| 64. |
In forced convective heat transfer, Stanton number (St), Nusselt number (Nu), Reynolds number (Re) and Prandtl number (Pr) are related as |
| A. | \(St = \frac{Nu\; Pr}{Re }\) |
| B. | \(St = \frac{Nu \;Re}{ Pr}\) |
| C. | St = Nu Pr Re |
| D. | \(St = \frac{Nu}{Re\; Pr}\) |
| Answer» B. \(St = \frac{Nu \;Re}{ Pr}\) | |
| 65. |
For flow through a pipe of radius R, the velocity and temperature distribution are as follows:\(u\left( {r,x} \right) = {C_1},and\ T\left( {r,x} \right) = {C_2}{\left[{1 - (\frac{r}{R})^3} \right]}\), where C1 and C2 are constants. The bulk mean temperature is given by \({T_m} = \frac{2}{{{u_m}{R^2}}}\mathop \smallint \limits_0^R u\left( {r,x} \right)T\left( {r,x} \right)rdr,\)with Um being the mean velocity of flow. The value of Tm is |
| A. | \(\frac{{0.5{C_2}}}{{{U_m}}}\) |
| B. | 0.5 C2 |
| C. | 0.6 C2 |
| D. | \(\frac{{0.6{C_2}}}{{{U_m}}}\) |
| Answer» D. \(\frac{{0.6{C_2}}}{{{U_m}}}\) | |
| 66. |
Peclet number is the product of: |
| A. | Grashof and Rayleigh number |
| B. | Reynolds and Prandtl number |
| C. | Grashof and Prandtl number |
| D. | Reynolds and Stanton number |
| Answer» C. Grashof and Prandtl number | |
| 67. |
Dropwise condensation usually occurs on |
| A. | glazed surface |
| B. | smooth surface |
| C. | oil surface |
| D. | coated surface |
| Answer» D. coated surface | |
| 68. |
Air is flowing over a hot plate at a temperature of 120 °C. If at a point Reynold number is increased by 4 times and Nusselt number is increased by 2 times, then the new value of Prandtl number will be: |
| A. | 2 times |
| B. | 4/9 times |
| C. | 1/2 times |
| D. | same |
| Answer» E. | |
| 69. |
If \(q_w'' = 5000\), and the convection heat transfer coefficient at the pipe outlet is 1000 W/m2K, the temperature in °C at the inner surface of the pipe at the outlet is |
| A. | 71 |
| B. | 76 |
| C. | 79 |
| D. | 81 |
| Answer» E. | |
| 70. |
Match Group A with Group B :Group AGroup BP : Biot number1 : Ratio of buoyancy to viscous forceQ : Grashof number2 : Ratio of inertia force to viscous forceR : Prandtl number3 : Ratio of momentum to thermal diffusivitiesS : Reynolds number4 : Ratio of internal thermal resistance to boundary layerthermal resistance |
| A. | P - 4 ,Q - 1 ,R - 3,S - 2 |
| B. | P - 4 ,Q - 3,R - 1,S - 2 |
| C. | P - 3,Q - 2,R - 1,S - 4 |
| D. | P - 2,Q - 1,R - 3,S - 4 |
| Answer» B. P - 4 ,Q - 3,R - 1,S - 2 | |
| 71. |
In cooling tower, water is cooled by the process of ________. |
| A. | Condensation |
| B. | Fusion |
| C. | Evaporation |
| D. | Sublimation |
| Answer» D. Sublimation | |
| 72. |
For which of these configurations is a minimum temperature difference required for natural convection to set in |
| A. | Fluid near a heated vertical plate |
| B. | Fluid near a heated plate inclined at 45° to the vertical |
| C. | Fluid over a heated horizontal plate |
| D. | Fluid near a heated cylinder |
| Answer» D. Fluid near a heated cylinder | |
| 73. |
For filmwise condensation, the heat transfer coefficient will be equal whether the tube is horizontal or vertical, when the ratio of length to diameter is |
| A. | 1.3 |
| B. | 2.87 |
| C. | 0.77 |
| D. | >10 |
| Answer» C. 0.77 | |
| 74. |
A pipe of 10 cm diameter and 10 m length is used for condensing steam on its outer surface. The average heat transfer coefficient hh (when the pipe is horizontal) is n times the average heat transfer coefficient hv (when the pipe is vertical). The value of n is: |
| A. | 2.44 |
| B. | 3.34 |
| C. | 4.43 |
| D. | 5.34 |
| Answer» B. 3.34 | |
| 75. |
A electric heater of exposed surface area 0.09 m2 and output 600 watts is designed to operate fully submersed in water. When the water is at 37°C and the surface coefficient of heat transfer is 285.3 W/m2-deg C, surface temperature of the heater will be |
| A. | 30.5°C |
| B. | 60.5°C |
| C. | 90.5°C |
| D. | 120.5°C |
| Answer» C. 90.5°C | |
| 76. |
For a fluid with Prandtl number Pr > 1, momentum boundary layer thickness |
| A. | Decreases rapidly compared to the thermal boundary layer thickness |
| B. | And thermal boundary layer thickness increase at the same rate |
| C. | Increases rapidly compared to the thermal boundary layer thickness |
| D. | And thermal boundary layer thickness decrease at the same rate |
| Answer» D. And thermal boundary layer thickness decrease at the same rate | |
| 77. |
A_SPHERE,_A_CUBE_AND_A_THIN_CIRCULAR_PLATE,_ALL_MADE_OF_THE_SAME_MATERIAL_AND_HAVING_THE_SAME_MASS_ARE_INITIALLY_HEATED_TO_THE_TEMPERATURE_OF_250_DEGREE_CELSIUS._WHEN_LEFT_IN_AIR_AT_ROOM_TEMPERATURE,_WHAT_WILL_BE_THEIR_RESPONSE_TO_COOLING??$ |
| A. | Cube will cool faster than sphere but slower than the circular plate |
| B. | They will cool at the same rate |
| C. | Sphere will cool faster |
| D. | Circular plate will cool at the slower rate |
| Answer» B. They will cool at the same rate | |
| 78. |
What is the value of convective coefficient of oil in case of forced convection? |
| A. | 1460-3000 W/m<sup>2</sup> K |
| B. | 460-3000 W/m<sup>2</sup> K |
| C. | 60-3000 W/m<sup>2</sup> K |
| D. | 160-3000 W/m<sup>2</sup> K |
| Answer» D. 160-3000 W/m<sup>2</sup> K | |
| 79. |
On a summer day, a scooter rider feels more comfortable while on the move than while at a stop light becaus? |
| A. | An object in motion captures less radiation |
| B. | Air has a low specific heat and hence it is cooler |
| C. | More heat is loss by convection and radiation while in motion |
| D. | Air is transparent to radiation and hence it is cooler than the body |
| Answer» E. | |
| 80. |
A body cooling from 80 degree Celsius to 70 degree Celsius takes 10 minutes when left exposed to environmental conditions. If the body is to cool further from 70 degree Celsius to 60 degree Celsius under the same external conditions, it will take |
| A. | Same time of 10 minutes |
| B. | More than 10 minutes |
| C. | Less than 10 minutes |
| D. | Time will depend upon the environmental conditions |
| Answer» C. Less than 10 minutes | |
| 81. |
A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter. The major portion of the heat transfer from the radiation is due to |
| A. | Combined conduction and radiation |
| B. | Radiation to the surroundings |
| C. | Better conduction |
| D. | Convection to the air |
| Answer» E. | |
| 82. |
Forced convection in a liquid bath is caused by |
| A. | Intense stirring by an external agency |
| B. | Molecular energy interactions |
| C. | Density difference brought about by temperature gradients |
| D. | Flow of electrons in a random fashion |
| Answer» B. Molecular energy interactions | |
| 83. |
Mark the system where heat transfer is given by forced convection |
| A. | Chilling effect of cold wind on warm body |
| B. | Fluid passing through the tubes of a condenser and other heat exchange equipment |
| C. | Heat flow from a hot pavement to surrounding atmosphere |
| D. | Heat exchange on the outside of cold and warm pipes |
| Answer» C. Heat flow from a hot pavement to surrounding atmosphere | |
| 84. |
Which of the following heat flow situations pertains to free or natural convection? |
| A. | Air conditioning installations and nuclear reactors |
| B. | Flow of water inside the condenser tubes |
| C. | Cooling of internal combustion engine |
| D. | Cooling of billets in atmosphere |
| Answer» E. | |
| 85. |
How many types of convection are there? |
| A. | 4 |
| B. | 3 |
| C. | 2 |
| D. | 1 |
| Answer» C. 2 | |
| 86. |
Conduction plus fluid flow in motion is known as |
| A. | Radiation |
| B. | Conduction |
| C. | Convection |
| D. | Heat exchanger |
| Answer» D. Heat exchanger | |