McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
Chapters
| 51. |
Water is used as a refrigerant in |
| A. | Vapour absorption cycle |
| B. | Steam jet refrigeration |
| C. | Vapour absorption cycle |
| D. | Cascade system |
| E. | None of the above |
| Answer» B. Steam jet refrigeration | |
| 52. |
During adiabatic saturation process on unsaturated air |
| A. | Dry bulb temperature remains constant |
| B. | Wet bulb temperature remains constant |
| C. | Dew point temperature remains constant |
| D. | Relative humidity remains constant |
| E. | None of the above |
| Answer» B. Wet bulb temperature remains constant | |
| 53. |
In a vapour compression refrigeration cycle, high head pressure is indicated which does not change even when compressor is stopped and allowed to cool. The probable cause may be |
| A. | High refrigerant charge |
| B. | Low refrigerant charge |
| C. | Air in the system |
| D. | High vapour pressure |
| E. | Any of the above |
| Answer» C. Air in the system | |
| 54. |
A critical temperature is the temperature |
| A. | Below which gas is always liquefied |
| B. | Above which a gas will never be liquefied |
| C. | Below which a gas does not obey gas laws |
| D. | Above which a gas may explode |
| E. | None of the above |
| Answer» B. Above which a gas will never be liquefied | |
| 55. |
A Salinometer |
| A. | Measure intensity of illumination |
| B. | Measures temperatures in cryogenic regions |
| C. | Measures solar radiation |
| D. | Measures sound level |
| E. | Measures density of brine |
| Answer» E. Measures density of brine | |
| 56. |
In cooling towers the heat is dissipated mainly by |
| A. | Freezing |
| B. | Convection |
| C. | Radiation |
| D. | Conduction |
| E. | Evaporation |
| Answer» E. Evaporation | |
| 57. |
Capacity of a domestic refrigerator is in the range |
| A. | 1 to 3 tonnes |
| B. | 7 to 10 tonnes |
| C. | 0.1 to 0.3 tonnes |
| D. | 3 to 5 tonnes |
| E. | 5 to 7 tonnes |
| Answer» C. 0.1 to 0.3 tonnes | |
| 58. |
If a refrigerator is directly exposed to sun rays |
| A. | It will stop working |
| B. | The refrigerant will leak |
| C. | There will be less cooling effect |
| D. | Frost will be formed on cabinet surface |
| E. | (A) and (B) above |
| Answer» C. There will be less cooling effect | |
| 59. |
A refrigerating system operates on the reversed Carnot cycle. The higher temperature of the refrigerant in the system is 40?C and the lower is - 15?C. The capacity is to be 10 tons. Neglecting all losses, the coefficient of performance of the system would be |
| A. | 2.67 |
| B. | 3.75 |
| C. | 9.41 |
| D. | 4.69 |
| E. | 7.36 |
| Answer» D. 4.69 | |
| 60. |
As warm air cools, its |
| A. | Relative humidity increases |
| B. | Relative humidity decreases |
| C. | There is no effect on moisture holding capacity |
| D. | Capacity to hold moisture increases |
| E. | Dew point occurs |
| Answer» B. Relative humidity decreases | |
| 61. |
In a small vapour compression cycle using capillary tubing for expansion, if suddenly uncondensed vapours enter the tubing, the result will be |
| A. | Improved refrigerating capacity |
| B. | Loss in refrigerating capacity |
| C. | Supply of superheated vapour to compressor |
| D. | Choking of drier |
| E. | All of the above |
| Answer» B. Loss in refrigerating capacity | |
| 62. |
In which section of a vapour compression system, the refrigerant is generally in the form of a wet vapour? |
| A. | Condenser outlet |
| B. | Expansion valve |
| C. | Evaporator |
| D. | Compressor |
| E. | Condenser inlet |
| Answer» C. Evaporator | |
| 63. |
In a vapour absorption system as compared to vapour compression system, the compressor is replaced by |
| A. | Receiver |
| B. | Expansion valve |
| C. | Evaporator |
| D. | Conderser |
| E. | Absorber and generator |
| Answer» E. Absorber and generator | |
| 64. |
In a refrigerating system work done per kg of air is 20 kcal and heat extracted per kg of air is 25 kcal. The quantity of refrigerant used is 10 kg. The coefficient of performance of the system would be |
| A. | 0.8 |
| B. | 12.5 |
| C. | 5 |
| D. | 8 |
| E. | 1.25 |
| Answer» E. 1.25 | |
| 65. |
If a one ton refrigeration machine, the significance of term "One ton" is that |
| A. | One ton of water can be converted into ice |
| B. | One ton of ice when melts from and at 0?C in 24 hours the refrigeration effect equivalent to that |
| C. | One ton water can be stored at a time |
| D. | One ton is the total weight of equipment |
| E. | One ton of refrigerant is used |
| Answer» B. One ton of ice when melts from and at 0?C in 24 hours the refrigeration effect equivalent to that | |
| 66. |
The change in temperature resulting from a gas expanding from one constant pressure, with no heat transfer and no external work other than to maintain the constant pressure is known as |
| A. | Dalton's law of partial pressures |
| B. | Kinetic theory of gases |
| C. | Avogadro's hypothesis |
| D. | Joule - Thomoson effect |
| E. | Law of conservation of energy |
| Answer» D. Joule - Thomoson effect | |
| 67. |
Anhydrous substance is |
| A. | Free of hydrogen and other chemicals containing hydrogen |
| B. | Dry substance |
| C. | Free of humidity |
| D. | Free of hydrogen |
| E. | Free of water especially water of crystallization |
| Answer» E. Free of water especially water of crystallization | |
| 68. |
No refrigerator using reversed Carnot cycle has been constructed because |
| A. | It is uneconomical |
| B. | It is less efficient |
| C. | It requires bulky machines |
| D. | 9.41 |
| E. | Isentropic portions of cycle require low speeds whereas isothermal protuons require high speeds |
| Answer» A. It is uneconomical | |
| 69. |
The statement: If a maximum of gases or vapours is enclosed in a container, each will exert its own pressure on the container entirely independent of the others and the total absolute pressure will be equal to the sum of the partial pressure exerted by each of the gases. This statement is known as |
| A. | Newton's law of gases |
| B. | Kinetic theory of gases |
| C. | Avogadro's hypothesis |
| D. | Fick's law |
| E. | Dalton's law of partial pressures. |
| Answer» E. Dalton's law of partial pressures. | |
| 70. |
Defrosting of evaporators is done because |
| A. | Frosting increases refrigerating effect |
| B. | Frosting retards heat flow |
| C. | Frosting is undersirable |
| D. | Frosting obstructs flow of refrigerant |
| E. | Frosting may cause damage to equipment |
| Answer» B. Frosting retards heat flow | |
| 71. |
No liquid can exist as a liquid at |
| A. | 100?C |
| B. | Zero pressure |
| C. | Zero viscosity |
| D. | 0?C |
| E. | 10,000 m height above the surface of earth |
| Answer» B. Zero pressure | |
| 72. |
Dischloromono fluoroethane is |
| A. | Freon 11 |
| B. | Freon 12 |
| C. | Freon 21 |
| D. | Freon 22 |
| E. | None of the above |
| Answer» D. Freon 22 | |
| 73. |
In a refrigeration system, if the compressor short cycles, the probable cause could be |
| A. | Intermittent contact in electric control circuit |
| B. | Dirty or iced evaporator |
| C. | Lack of refrigerant |
| D. | Overchange of refrigerant |
| E. | Any of the above |
| Answer» E. Any of the above | |
| 74. |
Reversed Carnot cycle assumes that all processes in the cycle are |
| A. | Non-flow only |
| B. | 10,000 m height above the surface of earth |
| C. | Transient flow |
| D. | Non flow or steady flow |
| E. | Steady flow only |
| Answer» D. Non flow or steady flow | |
| 75. |
Which of the following valves is used on domestic refrigerators |
| A. | Solenoid valve |
| B. | Expansion valve |
| C. | Spring safety valve |
| D. | Wheel valve |
| E. | None of the above |
| Answer» E. None of the above | |
| 76. |
A thermometer installed, in a vapour compression ammonia system, after the condenser shows elevated reading than the normal. It shows that |
| A. | Condenser needs cleaning |
| B. | Cooling tower or spray pond not handling the load properly |
| C. | Uneven water distribution over the condensing surfaces |
| D. | Any of the above |
| E. | None of the above |
| Answer» D. Any of the above | |
| 77. |
One a psychrometric chart cooling and humidification process using spray can be shown by |
| A. | A line parallel to wet bulb temperature lines |
| B. | A curve |
| C. | A line parallel to dry bulb temperature lines |
| D. | A horizontal line |
| E. | A vertical line |
| Answer» A. A line parallel to wet bulb temperature lines | |
| 78. |
In a vapour compression cycle the refrigerant immediately after expansion valve is in |
| A. | Liquid form |
| B. | Wet vapour form |
| C. | Dry vapour form |
| D. | Dry and saturated vapour form |
| E. | None of the above |
| Answer» B. Wet vapour form | |
| 79. |
If wet bulb temperature is same as dew point, the relative humidity of air will be |
| A. | 0 |
| B. | 25 |
| C. | 67 |
| D. | 100 |
| E. | 50 |
| Answer» D. 100 | |
| 80. |
A plant has one 300 ton and one 500 ton centrifugal unit. The total flow of brine is 6400 litres per minute. What should be the distribution of brine flow through each unit |
| A. | 3200 litres each |
| B. | 2400 litres through 300 ton plant and 4000 litres through 500 ton plant |
| C. | 4000 litres through 300 ton plant and 2400 litres through 500 ton plant |
| D. | Same brine should flow through both |
| E. | None of the above |
| Answer» C. 4000 litres through 300 ton plant and 2400 litres through 500 ton plant | |
| 81. |
Which of the following refrigerant has the lowest specific volume? |
| A. | Ammonia |
| B. | Freon 22 |
| C. | All the refrigerants have identical specific volume |
| D. | Freon 12 |
| E. | Carbondioxide |
| Answer» E. Carbondioxide | |
| 82. |
Which of the following refrigerant compressor is not classified as positive displacement compressor |
| A. | Reciprocating compressor |
| B. | Centrifugal compressor |
| C. | Rotary compressor |
| D. | Screw compressor |
| E. | None of the above |
| Answer» B. Centrifugal compressor | |
| 83. |
Class II group of refrigerants absorb sensible heat while giving refrigeration effect. Which of the following is a class II refrigerant |
| A. | Ammonia |
| B. | Carbondioxide |
| C. | Freon 12 |
| D. | Methyl chloride |
| E. | All of the above |
| Answer» D. Methyl chloride | |
| 84. |
The critical pressure of a liquid is the pressure |
| A. | Below which a liquid will always be in vapour form |
| B. | Above which a liquid will remain a liquid |
| C. | Above which a liquid will always turn into a vapour |
| D. | Above which a liquid will explode |
| E. | None of the above |
| Answer» B. Above which a liquid will remain a liquid | |
| 85. |
Frost on cooling coils |
| A. | Increases heat transfer |
| B. | Reduces evaporator temperature |
| C. | Improves COP of the system |
| D. | Acts as an insulation, increasing power consumption |
| E. | Reduces power consumption |
| Answer» D. Acts as an insulation, increasing power consumption | |
| 86. |
The coefficient of performance of a domestic refrigerator as compared to that of an air conditioner is gererally |
| A. | Less |
| B. | Cannot be compared |
| C. | More |
| D. | Air conditioner performance depends on whether conditions |
| E. | Same |
| Answer» A. Less | |
| 87. |
The leakage in a refrigeration system using freon is detected by |
| A. | Acetylene torch |
| B. | Halide torch |
| C. | Sulphur stricks |
| D. | Soap and water |
| E. | Any of the above |
| Answer» B. Halide torch | |
| 88. |
The critical temperature for Freon 12 is |
| A. | Above 100?C |
| B. | Less than - 50?C |
| C. | Around - 20?C |
| D. | 0?C |
| E. | Around 50?C |
| Answer» A. Above 100?C | |
| 89. |
In a vapour compression cycle the lowest temperature occurs in |
| A. | Evaporator |
| B. | Expansion valve |
| C. | Condenser |
| D. | Receiver |
| E. | Compressor |
| Answer» A. Evaporator | |
| 90. |
If dry bulb temperature is 25?C and wet bulb temperature is 18?C, then which of the following temperatures could possibly represent dew point? |
| A. | 14?C |
| B. | 25?C |
| C. | 40?C |
| D. | 43?C |
| E. | 18?C |
| Answer» A. 14?C | |
| 91. |
The effect of under cooling the refrigerant is to |
| A. | Reducing the COP of the cycle |
| B. | Increase the COP of the cycle |
| C. | Reduce the refrigerating effect |
| D. | Increase the super heat of vapour |
| E. | None of the above |
| Answer» B. Increase the COP of the cycle | |
| 92. |
Clear ice |
| A. | Is pure ice |
| B. | Contains dissolved air |
| C. | Contains dissolved gases |
| D. | Is produced by blowing air during freezing |
| E. | None of the above |
| Answer» D. Is produced by blowing air during freezing | |
| 93. |
Two thermometers are constructed in the same way except that one has a spherical bulb and the other an elongated cylindrical bulb. Which one will respond quickly to temperature change? |
| A. | Spherical bulb thermometer |
| B. | Cylindrical bulb thermometer |
| C. | Both will respond in identical manner |
| D. | Cannot be ascertained on the basis of information provided |
| E. | None of the above |
| Answer» B. Cylindrical bulb thermometer | |
| 94. |
A low wet bulb temperature indicates |
| A. | Very cool air |
| B. | Very low humidity |
| C. | Very low atmospheric temperature |
| D. | (A) and (B) above |
| E. | (A) and (C) above |
| Answer» D. (A) and (B) above | |
| 95. |
On a psychrometric chart sensible heating or cooling is represented by |
| A. | A horizontal line |
| B. | A vertical line |
| C. | Inclined line |
| D. | Curved line |
| E. | None of the above |
| Answer» A. A horizontal line | |
| 96. |
During sensible heating of air |
| A. | Dry bulb temperature increases while enthalpy of moist air decreases |
| B. | 10,000 m height above the surface of earth |
| C. | Both dry bulb temperature as well as enthalpy decrease |
| D. | Both dry bulb temperature as well as enthalpy increase |
| E. | Dry bulb temperature decreases while enthalpy of moist air increases |
| Answer» D. Both dry bulb temperature as well as enthalpy increase | |
| 97. |
Air and other non-condensable gases (foul gases) get into a refrigeration system through |
| A. | Decomposition of refrigerant in contact with impurities |
| B. | Breakdown of oil |
| C. | Under vacuum operation or during maintenance work |
| D. | Corrosion |
| E. | Any of the above |
| Answer» E. Any of the above | |
| 98. |
Refrigerant 717 is |
| A. | Freon 22 |
| B. | Air |
| C. | Freon 12 |
| D. | Carbondioxide |
| E. | Ammonia |
| Answer» E. Ammonia | |
| 99. |
The relation between vapour pressure to the enthalpy of vaporisation is expressed in |
| A. | Vander wall's equation |
| B. | Energy equation |
| C. | Maxwell's equation |
| D. | Clausius Clapeyron equation |
| E. | Lewis equation |
| Answer» D. Clausius Clapeyron equation | |
| 100. |
For a sensible heating the air is passed over a heating coil which may be |
| A. | Heated by electric resistance |
| B. | Heated by passing hot water through the coil |
| C. | Heated by passing steam through the coil |
| D. | Heated by direct solar radiations |
| E. | Heated by any of the above methods |
| Answer» E. Heated by any of the above methods | |
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