MCQOPTIONS
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MCQOPTIONS
This section includes 97 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. |
In a refrigerating machine, if the lower temperature is fixed, then the C.O.P of the machine can be increased by |
| A. | Increasing the higher temperature |
| B. | Decreasing the higher temperature |
| C. | Operating the machine at a lower speed |
| D. | Operating the machine at a higher speed |
| Answer» C. Operating the machine at a lower speed | |
| 52. |
A Carnot-refrigerator has a COP of 6. What is the ratio of the lower to the higher absolute temperature? |
| A. | 1/6 |
| B. | 7/8 |
| C. | 6/7 |
| D. | 1/7 |
| Answer» D. 1/7 | |
| 53. |
In a vapour compression refrigerator, the heat rejected in condenser is 1500 kJ/kg of refrigerant flow and the work done by compressor is 250 kJ/kg. The COP of the refrigerator is: |
| A. | 5 |
| B. | 6 |
| C. | 7 |
| D. | 8 |
| Answer» B. 6 | |
| 54. |
Air refrigeration system operates on |
| A. | Carnot cycle |
| B. | Reversed Carnot cycle |
| C. | Rankine cycle |
| D. | Bell Coleman cycle |
| Answer» E. | |
| 55. |
A capillary tube is employed in a refrigeration cycle to ______. |
| A. | produce a cooling effect |
| B. | reduce pressure of the refrigerant |
| C. | control temperature of the refrigerated space |
| D. | control flow of the refrigerant |
| Answer» C. control temperature of the refrigerated space | |
| 56. |
Aqua ammonia solution used in a vapour absorption refrigeration system is a solution of ammonia in ______ |
| A. | CF3 |
| B. | H2O |
| C. | LiBr |
| D. | H2O2 |
| Answer» C. LiBr | |
| 57. |
Liquid sub cooler in Vapour Compression Refrigeration System will |
| A. | Prevent the entry of liquid into compressor |
| B. | Increases net refrigeration effect |
| C. | Reduce work of compression |
| D. | Increase work of compression |
| Answer» C. Reduce work of compression | |
| 58. |
In an ideal Vapour Compression Refrigeration cycle the enthalpy values at salient points are as follows:At inlet to compressor : 1500 kJ/kgAt outlet to compressor : 1800 kJ/kgAt inlet to evaporator : 300 kJ/kgWhat is the COP of the cycle? |
| A. | 3 |
| B. | 4 |
| C. | 5 |
| D. | 6 |
| Answer» C. 5 | |
| 59. |
Consider the following functions:1) Minimizing friction2) Sealing the gas between suction and discharge ports3) As a coolant to transfer heat from the crankcase to the compressor shell4) To dampen the noise generated by moving partsWhich of the above function do lubricants in refrigeration systems perform? |
| A. | 1, 2, 3, and 4 |
| B. | 1 and 2 only |
| C. | 2 and 3 only |
| D. | 3 and 4 only |
| Answer» B. 1 and 2 only | |
| 60. |
A domestic food freezer maintains a temperature of –15°C. The ambient air temperature is 30°C. If heat leaks into the freezer at the continuous rate of 1.75 kJ/s, the least power necessary to pump this heat out continuously will be nearly |
| A. | 0.1 kW |
| B. | 0.2 kW |
| C. | 0.3 kW |
| D. | 0.4 kW |
| Answer» D. 0.4 kW | |
| 61. |
In a refrigeration system, subcooling |
| A. | increases COP |
| B. | decreases COP |
| C. | increases the work required |
| D. | decreases the work required |
| Answer» B. decreases COP | |
| 62. |
For the same pressure the saturation temperature of ammonia is |
| A. | higher than saturation temperature of water |
| B. | lower than saturation temperature of water |
| C. | same as the saturation temperature of water |
| D. | depends on concentration of ammonia in water |
| Answer» C. same as the saturation temperature of water | |
| 63. |
A Carnot heat pump works between 27° C and 327°C. What will be its COP? |
| A. | 0.09 |
| B. | 1 |
| C. | 1.09 |
| D. | 2 |
| Answer» E. | |
| 64. |
For vapour compression system using R717 the material of pipe is |
| A. | Steel |
| B. | Copper |
| C. | Brass |
| D. | Aluminium |
| Answer» B. Copper | |
| 65. |
A package type Air conditioner has a capacity upto around |
| A. | 1 ton |
| B. | 100 tons |
| C. | 20 tons |
| D. | none of the above |
| Answer» C. 20 tons | |
| 66. |
In a vapor compression system, the highest temperature of the refrigerant during the cycle occurs after |
| A. | evaporation |
| B. | compression |
| C. | condensation |
| D. | expansion |
| Answer» C. condensation | |
| 67. |
In vapour compression refrigeration system, heat rejected as compared to heat absorbed is |
| A. | More |
| B. | Less |
| C. | Equal |
| D. | Depends on the refrigerant used |
| Answer» B. Less | |
| 68. |
Consider the following statements in respect of vapor compression refrigeration units:1. In actual units the refrigerant leaving the evaporator is superheated2. Superheating of refrigerant at the exit of evaporator increases the refrigerating effect3. The superheating of refrigerant increases the work of the compressorWhich of the above statements are correct? |
| A. | 1 and 2 only |
| B. | 1 and 3 only |
| C. | 2 and 3 only |
| D. | 1, 2 and 3 |
| Answer» E. | |
| 69. |
If a Carnot refrigerator and a Carnot heat pump are operating between the same two thermal reservoirs, and the COP of the refrigerator is 2.5, then COP of the heat pump will be: |
| A. | 4.5 |
| B. | 1.5 |
| C. | 2.5 |
| D. | 3.5 |
| Answer» E. | |
| 70. |
A house refrigerator with its door open is switched on in a closed room. The air in the room is |
| A. | Cooled |
| B. | Remains at same temperature |
| C. | Heated |
| D. | Heated or cooled depending on atmospheric pressure |
| Answer» D. Heated or cooled depending on atmospheric pressure | |
| 71. |
A cold storage plant of 20 tonne of refrigerator capacity operates between 200 K and 300 K. The power required to run the plant if the plant has half COP of a Carnot cycle (Tonne of refrigerator = 3.5 kW) is |
| A. | 50 kW |
| B. | 60 kW |
| C. | 70 kW |
| D. | 80 kW |
| Answer» D. 80 kW | |
| 72. |
In isentropic compression, similar to the aircraft refrigeration cycle, what is ram efficiency? |
| A. | It is proportional to mass flow rate |
| B. | Ratio of input to output ram pressure |
| C. | Ratio of aircraft velocity to sonic velocity |
| D. | Ratio of actual pressure rise to isentropic pressure |
| Answer» C. Ratio of aircraft velocity to sonic velocity | |
| 73. |
A cold coffee shop uses a refrigerator with COP 2.5 for cooling drinking water at 0.42 litre/min from 18°C to 10°C. The specific heat capacity of water is 4.18 kJ/kg-K. power consumption by refrigerator will be |
| A. | 92.9 W |
| B. | 75 W |
| C. | 85 W |
| D. | 120 W |
| Answer» B. 75 W | |
| 74. |
In an extra humid atmosphere which one of the following motor would you select? |
| A. | Open type |
| B. | Semi-protected |
| C. | Drip-proof |
| D. | Totally enclosed fan cooled |
| Answer» E. | |
| 75. |
Domestic refrigerator working on vapour compression cycle uses the following type of expansion device |
| A. | Electrically operated throttling valve |
| B. | Manually operated valve |
| C. | Thermostatic valve |
| D. | Capillary tube |
| Answer» E. | |
| 76. |
Pyrometer is a device which is related to- |
| A. | Density measurements |
| B. | Pressure measurements |
| C. | Temperature measurements |
| D. | Volume measurements |
| Answer» D. Volume measurements | |
| 77. |
In a triple fluid vapour absorption refrigeration system, hydrogen gas is used to: |
| A. | provide vapour seal |
| B. | reduce partial pressure of refrigerant in evaporator |
| C. | improves system performance |
| D. | circulate the refrigerant |
| Answer» C. improves system performance | |
| 78. |
A refrigerating system operates on a reversed Carnot cycle. The higher temperature of the refrigerant in the system is 35°C and the lower temperature is -15°C. The COP of the system will be: |
| A. | 0.19 |
| B. | 5.16 |
| C. | 1.93 |
| D. | 0.51 |
| Answer» C. 1.93 | |
| 79. |
An ideal refrigerating machine works between the temperature limits of 45°C and -8°C . The power required per ton of refrigeration is |
| A. | 1.0 kW |
| B. | 1.2 kW |
| C. | 0.8 kW |
| D. | 0.7 kW |
| Answer» E. | |
| 80. |
A heat engine is supplied heat at the rate of 1700 kJ/min and gives an output of 9 kW. The thermal efficiency will be around |
| A. | 31.76% |
| B. | 35.76% |
| C. | 42.85% |
| D. | 45.85% |
| Answer» B. 35.76% | |
| 81. |
An ideal closed-cycle gas turbine plant is working between the temperatures 927 °C and 27 °C using air as working fluid. The pressure ratio for maximum output is |
| A. | 11.3 |
| B. | 13.3 |
| C. | 15.3 |
| D. | 17.3 |
| Answer» B. 13.3 | |
| 82. |
In refrigeration cycle sub cooling occurs when |
| A. | Latent heat from refrigerant is removed |
| B. | Sensible heat from refrigerant is removed |
| C. | Refrigerant has low latent heat removed |
| D. | Refrigerant has high thermal conductivity |
| Answer» C. Refrigerant has low latent heat removed | |
| 83. |
A reversible engine has ideal thermal efficiency of 30%. When it is used as refrigerating machine with all other conditions unchanged, the coefficient of performance will be |
| A. | 1.33 |
| B. | 2.33 |
| C. | 3.33 |
| D. | 4.33 |
| Answer» C. 3.33 | |
| 84. |
In a vapor compression system, the condition of refrigerant before entering the compressor is: |
| A. | Saturated liquid |
| B. | Wet vapour |
| C. | Superheated vapour |
| D. | Dry saturated vapour |
| Answer» E. | |
| 85. |
In a vapour absorption refrigeration, heat is rejected in |
| A. | Generator only |
| B. | Condenser only |
| C. | Condenser and absorber |
| D. | Absorber only |
| Answer» D. Absorber only | |
| 86. |
In aqua-ammonia and Li-Br water absorption refrigeration system, the refrigerants are respectively |
| A. | water and water |
| B. | water and Li-Br |
| C. | ammonia and Li-Br |
| D. | ammonia and water |
| Answer» E. | |
| 87. |
A 10-tonne refrigeration system consumes 10 kW of electrical energy. Its Coefficient of Performance will be _________. |
| A. | 10 |
| B. | 3.5 |
| C. | 0.35 |
| D. | 35 |
| Answer» C. 0.35 | |
| 88. |
A Carnot refrigeration cycle absorbs heat at 270 K and rejects it at 300 K. Calculate the C.O.P of this refrigeration cycle. |
| A. | 9 |
| B. | 10 |
| C. | 0.11 |
| D. | 0.1 |
| Answer» B. 10 | |
| 89. |
In a vapour absorption refrigerator, the temperature of evaporator and ambient are 10°C and 30°C respectively. If the COP of the system is 2, estimate the generator temperature. |
| A. | 90°C |
| B. | 85°C |
| C. | 80°C |
| D. | 75°C |
| Answer» D. 75°C | |
| 90. |
A good refrigerant should have _________. |
| A. | High latent heat of vaporization and low freezing point |
| B. | High operating pressure and low freezing point |
| C. | High specific volume and high latent heat of vaporization |
| D. | Low coefficient of performance and low freezing point |
| Answer» B. High operating pressure and low freezing point | |
| 91. |
For Ammonia refrigeration system, the pipe for carrying refrigerant shall be made of following material: |
| A. | brass |
| B. | copper |
| C. | steel or wrought iron |
| D. | aluminium |
| Answer» D. aluminium | |
| 92. |
In an ideal vapour compression refrigeration cycle, the specific enthalpy of refrigerant (in kJ/kg) at the following states is given as:Inlet of condenser : 283Exit of condenser : 116Exit of evaporator : 232The COP of this cycle is |
| A. | 2.27 |
| B. | 2.75 |
| C. | 3.27 |
| D. | 3.75 |
| Answer» B. 2.75 | |
| 93. |
A Carnot cycle which operates between the temperatures of 400 K and 300 K. If 20000 kcal/hr of heat is supplied, the work output will be |
| A. | 3000 kcal/hr |
| B. | 4000 kcal/hr |
| C. | 5000 kcal/hr |
| D. | 6000 kcal/hr |
| Answer» D. 6000 kcal/hr | |
| 94. |
If the domestic refrigerator is kept in an insulated room, with its door open |
| A. | the temperature of the room shall decrease after sometime |
| B. | the temperature of the room shall increase after sometime |
| C. | the temperature of the room shall remain unaffected |
| D. | nothing can be predicted about the temperature of the room |
| Answer» C. the temperature of the room shall remain unaffected | |
| 95. |
In the figure shown above, E is the heat engine with efficiency of 0.4 and R is the refrigerator. If Q2 + Q4 = 3Q1 The COP of the refrigerator will be |
| A. | 3.0 |
| B. | 4.5 |
| C. | 5.0 |
| D. | 5.5 |
| Answer» D. 5.5 | |
| 96. |
A refrigeration system components are assembled, evacuated and charged by R1349. Which of the following statement is true? |
| A. | Thermal capacity of heat pump and refrigerating machine will be same |
| B. | Thermal capacity of refrigerating machine will be higher than heat pump |
| C. | Heat pump will have higher thermal capacity than refrigerating machine |
| D. | Thermal capacity relationship can not be predicted. |
| Answer» D. Thermal capacity relationship can not be predicted. | |
| 97. |
In a vapor compression refrigeration system, the sub-cooling of refrigerant in the condenser results in: |
| A. | Decrease in COP of the system |
| B. | Decrease in the size of the condenser |
| C. | Increase in the size of the evaporator |
| D. | Increase in the size of the compressor |
| Answer» D. Increase in the size of the compressor | |