MCQOPTIONS
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MCQOPTIONS
This section includes 968 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTDin parallel flow to the LMTD in counter flow is always |
| A. | < 1 |
| B. | > 1 |
| C. | 1 |
| D. | ∞ |
| Answer» B. > 1 | |
| 52. |
For a cold dilute feed to produce thick viscous liquor, backward feeding as compared toforward feeding results in |
| A. | Increased economy |
| B. | Decreased economy |
| C. | Lower capacity |
| D. | No effect on economy |
| Answer» B. Decreased economy | |
| 53. |
In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to(where, D = inside diameter of shell). |
| A. | 0.25 D |
| B. | 0.50 D |
| C. | 0.75 D |
| D. | None of these |
| Answer» D. None of these | |
| 54. |
For __________ Prandtl number values, the heat conduction will be negligible in the bufferzone. |
| A. | Extremely low |
| B. | Low |
| C. | High |
| D. | No |
| Answer» D. No | |
| 55. |
In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to__________ the velocity head. |
| A. | Twice |
| B. | Four times |
| C. | Square root of |
| D. | Square of |
| Answer» C. Square root of | |
| 56. |
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions? Assume that the conductive heat transfer co-efficient is infinitely large. |
| A. | 5 minutes |
| B. | 10 minutes |
| C. | 20 minutes |
| D. | 40 minutes |
| Answer» B. 10 minutes | |
| 57. |
Radiant energy received by a body is proportional to (where, d = the distance between theobject emitting radiation and that receiving it.) |
| A. | √d |
| B. | d |
| C. | d2 |
| D. | d1.5 |
| Answer» D. d1.5 | |
| 58. |
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluidflowing through a heated pipe? |
| A. | 0.5 |
| B. | < 0.5 |
| C. | > 0.6 |
| D. | < 0.1 |
| Answer» D. < 0.1 | |
| 59. |
Moisture would find its way into insulation by vapour pressure unless it isprevented 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. | |
| 60. |
The local surface conductance for laminar film condensation on vertical surface is(where, t = film thickness) |
| A. | ∝ t |
| B. | ∝ 1/t |
| C. | ∝ √t |
| D. | Independent of 't' |
| Answer» C. ∝ √t | |
| 61. |
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. |
| A. | Boiling point |
| B. | Dynamic viscosity |
| C. | Kinematic viscosity |
| D. | Density |
| Answer» B. Dynamic viscosity | |
| 62. |
Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2.°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the |
| A. | Higher condensing film co-efficient is desired |
| B. | Condensate is corrosive in nature |
| C. | Lower pressure drop through the exchanger is desired |
| D. | Temperature of the incoming vapor is very high |
| Answer» C. Lower pressure drop through the exchanger is desired | |
| 63. |
The Stefan-Boltzmann constant depends on the |
| A. | Medium |
| B. | Temperature |
| C. | Surface |
| D. | None of these |
| Answer» E. | |
| 64. |
To reduce the tube side pressure drop for the same flow rate, the heat exchangerrecommended is |
| A. | 1-2 heat exchanger |
| B. | 1-1 heat exchanger |
| C. | 3-2 heat exchanger |
| D. | 2-4 heat exchanger |
| Answer» C. 3-2 heat exchanger | |
| 65. |
The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2 .K. At steady state, the temperature of the right face in °C is |
| A. | 77.2 |
| B. | 71.2 |
| C. | 63.8 |
| D. | 48.7 |
| Answer» E. | |
| 66. |
Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (∆t1 - ∆t2)/ln(∆t1/∆t2)], which one is subject to the largest deviation in practice ? |
| A. | Constant overall heat transfer co-efficient. |
| B. | Constant rate of fluid flow |
| C. | Constant specific heat |
| D. | No partial phase change in the system |
| Answer» C. Constant specific heat | |
| 67. |
A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is |
| A. | 5.6 |
| B. | 0.025 |
| C. | 3.5 |
| D. | 0.0035 |
| Answer» C. 3.5 | |
| 68. |
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity ofinsulating 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 | |
| 69. |
For shell and tube heat exchanger, with increasing heat transfer area, the purchased costper unit heat transfer area |
| A. | Increases |
| B. | Decreases |
| C. | Remain constant |
| D. | Passes through a maxima |
| Answer» E. | |
| 70. |
A measure of the extent to which viscous heating is important relative to the heat flowresulting from the impressed temperature difference is represented by the __________ number. |
| A. | Condensation |
| B. | Grashoff |
| C. | Stanton |
| D. | Brinkman |
| Answer» E. | |
| 71. |
Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of |
| A. | 1 :1 |
| B. | 2: 1 |
| C. | 1 : 2 |
| D. | 4 : 1 |
| E. | 1 : 4. |
| Answer» D. 4 : 1 | |
| 72. |
Thickness of thermal boundary layer is more compared to that of hydrodynamic boundarylayer, when the value of Prandtl number is |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | > 5 |
| Answer» C. > 1 | |
| 73. |
A non-dimensional number generally associated with natural convection heattransfer is |
| A. | Grashoff number |
| B. | Nusselt number |
| C. | Weber number |
| D. | Prandtl number |
| E. | Reynold number. |
| Answer» B. Nusselt number | |
| 74. |
Conductance is given by (where, x = thickness, A = heat flow area, K = thermalconductivity.) |
| A. | x/KA |
| B. | KA/x |
| C. | K/Ax |
| D. | A/Kx |
| Answer» C. K/Ax | |
| 75. |
Absorptivity of a perfect black body is unity. Which of the following has maximumabsorptivity? |
| A. | Aluminium foil |
| B. | Refractory bricks |
| C. | Iron plate |
| D. | Coke breeze |
| Answer» E. | |
| 76. |
The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipein laminar flow are |
| A. | Re.Gz |
| B. | Nu, Pr |
| C. | Nu, Pr, Re |
| D. | Nu, Gz |
| Answer» E. | |
| 77. |
Minimum recommended baffle spacing in a shell and tube heat exchanger is about(where, D = shell diameter). |
| A. | 0.2 D |
| B. | 0.5 D |
| C. | 0.66 D |
| D. | 0.80 D |
| Answer» B. 0.5 D | |
| 78. |
Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface between B and C will be at a temperature of __________ °C. |
| A. | 40 |
| B. | 95 |
| C. | 70 |
| D. | 50 |
| Answer» D. 50 | |
| 79. |
Kirchoff‟s law applies to __________ radiation. |
| A. | Total |
| B. | Monochromatic |
| C. | Both (A) & (B) |
| D. | Neither (A) nor (B) |
| Answer» D. Neither (A) nor (B) | |
| 80. |
Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirtdeposited 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 | |
| 81. |
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 | |
| 82. |
According to Stefan’s law, the total radiation from a black body per second perunit area is proportional to |
| A. | absolute temperature |
| B. | T2 |
| C. | T5 |
| D. | t |
| E. | l/T. |
| Answer» E. l/T. | |
| 83. |
Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostlyby |
| A. | Eddies current |
| B. | Conduction |
| C. | Convection |
| D. | None of these |
| Answer» C. Convection | |
| 84. |
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 | |
| 85. |
In Joule's experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2 . Neglecting the heat capacity of agitator, the temperature of water (in °C) is |
| A. | 40.5 |
| B. | 34.4 |
| C. | 26.8 |
| D. | 25 |
| Answer» C. 26.8 | |
| 86. |
The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti- T0)/ln (ri /r0). For cylinder of very thin wall, q can be approximated by |
| A. | q = [2π k (Ti + T0)/2]/ln (ri /r0) |
| B. | q = 2π ri k (Ti- T0)/(r0/ri) |
| C. | q = 2π k (Ti- T0)/(r0/ri) |
| D. | q = 2π k (Ti- T0)/[(r0 + ri)/2] |
| Answer» E. | |
| 87. |
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 | |
| 88. |
At constant temperature, the thermal conductivities of gases __________ with rise inpressure. |
| A. | Decrease |
| B. | Increase |
| C. | Remain unchanged |
| D. | May increase or decrease; depends on the pressure |
| Answer» B. Increase | |
| 89. |
The equation, (NSt × N 2/3 Pr) = f/2, is the __________ analogy. |
| A. | Colburn |
| B. | Reynolds |
| C. | Prandtl |
| D. | None of these |
| Answer» B. Reynolds | |
| 90. |
The energy distribution of an ideal reflector at higher temperatures is largely inthe 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 | |
| 91. |
In case of parallel flow heat exchanger, the lowest temperature theoretically attainable bythe hot fluid is __________ the outlet temperature of the cold fluid. |
| A. | Equal to |
| B. | More than |
| C. | Less than |
| D. | Either more or less than (depending upon the fluid) |
| Answer» B. More than | |
| 92. |
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing isrespectively (where, D = inside diameter of the shell) |
| A. | D/5 and D |
| B. | D/2 and 2 D |
| C. | D/4 and 2 D |
| D. | D and 2 D |
| Answer» B. D/2 and 2 D | |
| 93. |
In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at theentrance of the tube is |
| A. | Infinity |
| B. | Zero |
| C. | Same as average heat transfer co-efficient for tube side |
| D. | None of these |
| Answer» B. Zero | |
| 94. |
Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparentbody, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be |
| A. | 0.35 |
| B. | 0.45 |
| C. | 0.55 |
| D. | 0.85 |
| Answer» C. 0.55 | |
| 95. |
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 | |
| 96. |
For evaporation of viscous solution in a multiple effect evaporator, the preferred feedingscheme is |
| A. | Forward |
| B. | Backward |
| C. | Parallel |
| D. | None of these |
| Answer» C. Parallel | |
| 97. |
1000 kg of wet solids are to be dried from 60% to 20% moisture (by weight). The mass ofmoisture removed in kg is |
| A. | 520 |
| B. | 200 |
| C. | 400 |
| D. | 500 |
| Answer» D. 500 | |
| 98. |
Pick up the wrong case. Heat flowing from one side to other depends directlyon |
| A. | face area |
| B. | time |
| C. | thickness |
| D. | temperature difference |
| E. | thermal conductivity. |
| Answer» D. temperature difference | |
| 99. |
Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid |
| A. | For fluids in laminar flow |
| B. | For fluids in turbulent flow |
| C. | When Grashoff number is very important |
| D. | For liquid metals |
| Answer» C. When Grashoff number is very important | |
| 100. |
The interchange factor for radiation heat transfer from surface 'x' to surface 'y' in case of an infinite parallel planes with emissivities εx & εy is given by |
| A. | εx + εy |
| B. | εx . εy |
| C. | 1/εx + 1/εy |
| D. | (εx + εy)/( εx + εy - εx . εy) |
| Answer» E. | |