MCQOPTIONS
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MCQOPTIONS
This section includes 55 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In an SI unit, one ton of refrigeration is |
| A. | 210 kJ/min |
| B. | 21 kJ/min |
| C. | 420 kJ/min |
| D. | 840 kJ/min |
| Answer» B. 21 kJ/min | |
| 2. |
In a multi-stage vapour compression refrigeration system, which of the following options is false as compared to single stage compression? |
| A. | The work compression is increased |
| B. | Volumetric efficiency increases |
| C. | Leakages across piston are reduced |
| D. | Lighter flywheel is required |
| Answer» B. Volumetric efficiency increases | |
| 3. |
If a refrigeration compressor using a thermostat as a primary controller is running continuously without significantly lowering the temperature in the refrigerated space, which of the following is most likely the trouble? |
| A. | A shortage of compressor oil |
| B. | A shortage of refrigerant |
| C. | Warm food in the refrigerator |
| D. | Excessive condenser cooling water |
| Answer» C. Warm food in the refrigerator | |
| 4. |
During chemical dehumidification process of air |
| A. | Dry bulb temperature and specific humidity decrease |
| B. | Dry bulb temperature increases and specific humidity decreases |
| C. | Dry bulb temperature decreases and specific humidity increases |
| D. | Dry bulb temperature and specific humidity increases |
| Answer» C. Dry bulb temperature decreases and specific humidity increases | |
| 5. |
In an Electrolux refrigerator, a thermo-siphon bubble pump is used to lift the |
| A. | weak aqua solution from the generator to the separator |
| B. | weak aqua solution from the separator to the absorber |
| C. | strong aqua solution from the generator to the separator |
| D. | strong aqua solution from the generator to the evaporator |
| Answer» B. weak aqua solution from the separator to the absorber | |
| 6. |
During a refrigeration cycle, heat is rejected by the refrigerant in a: |
| A. | Compressor |
| B. | Condenser |
| C. | Evaporator |
| D. | Expansion valve |
| Answer» C. Evaporator | |
| 7. |
Identify the incorrect statement, from the following options:An air refrigeration cycle ______ |
| A. | Operates on reverse Brayton cycle |
| B. | Employs air as the refrigerant |
| C. | Is used for air conditioning in airplanes |
| D. | Heat rejection and heat removal from the cooled space are constant volume processes |
| Answer» E. | |
| 8. |
In high-speed aircraft flying at high altitudes, why is the cooling of the cabin required even if temperature outside is very low? |
| A. | Due to the absence of solar radiation |
| B. | To improve fuel efficiency |
| C. | Due to large internal heat generation |
| D. | Since outside pressure is very high |
| Answer» D. Since outside pressure is very high | |
| 9. |
Coefficient of performance of a commercially used refrigerator would be close to |
| A. | 40% |
| B. | 85% |
| C. | 1.5 |
| D. | 3.5 |
| Answer» E. | |
| 10. |
An ideal refrigerator maintains a temperature of – 23°C when placed inside a room at 27°C. Heat infiltration into the refrigeration is 0.5 kJ/s. The power required to pump the heat out is: |
| A. | 0.034 kW |
| B. | 0.45 kW |
| C. | 55 W |
| D. | 0.1 kW |
| Answer» E. | |
| 11. |
Consider the following statements:An expansion device in a refrigeration system1. reduces the pressure from the condenser to the evaporator2. regulates the flow of the refrigerant to the evaporator depending on the load3. is essentially a restriction offering resistance to flowWhich 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. | |
| 12. |
In actual refrigeration systems, the compressor handles vapours only. What is this process commonly referred to as? |
| A. | Gas compression |
| B. | Phase compression |
| C. | Dry compression |
| D. | Wet compression |
| Answer» D. Wet compression | |
| 13. |
One ton of refrigerator is equal to the refrigeration effect corresponding to melting of 1000 kg of ice: |
| A. | In 1 hour |
| B. | In 1 minute |
| C. | In 24 hours |
| D. | In 12 hours |
| Answer» D. In 12 hours | |
| 14. |
A nozzle is not used in a: |
| A. | Jet engine |
| B. | Steam turbine |
| C. | Vapor compression refrigeration system |
| D. | Rocket |
| Answer» D. Rocket | |
| 15. |
1 ton of refrigeration implies heat transfer at the rate of |
| A. | 210 kJ/min |
| B. | 210 kJ/sec |
| C. | 1000 kJ/hr |
| D. | 2 kJ/hr |
| Answer» B. 210 kJ/sec | |
| 16. |
An air-conditioning system operating on the reversed Carnot cycle is required to remove heat from the room at a rate of 25 kW to maintain its temperature constant at 20° C. The temperature of the surroundings being 35°C, the power required to operate this air-conditioning system will be |
| A. | 1.28 kW |
| B. | 4.02 kW |
| C. | 5.12 kW |
| D. | 12.80 kW |
| Answer» B. 4.02 kW | |
| 17. |
In a vapour compression refrigeration system, liquid to the suction heat exchanger is used to |
| A. | Keep the COP constant |
| B. | Prevent the liquid refrigerant from entering the compressor |
| C. | Sub-cool the liquid refrigerant leaving the condenser |
| D. | Sub-cool the vapour refrigerant from the evaporator |
| Answer» D. Sub-cool the vapour refrigerant from the evaporator | |
| 18. |
Bell – Coleman cycle is applicable to: |
| A. | Vapour compressor refrigeration |
| B. | Vapor absorption refrigeration |
| C. | Air refrigeration |
| D. | All of them |
| Answer» D. All of them | |
| 19. |
500 kJ of heat is removed from a cooled space, in a reversed Carnot cycle refrigerator, by an evaporator by refrigerant at – 23oC. The change in entropy of the refrigerant is: |
| A. | 2 kJ/K |
| B. | – 2 kJ/K |
| C. | 21.74 kJ/oC |
| D. | 0.5 kJ/K |
| Answer» B. – 2 kJ/K | |
| 20. |
In refrigeration system, energy efficiency ratio is |
| A. | Watt refrigeration effect/Watt input |
| B. | kW Input/Tons refrigeration effect |
| C. | kW refrigeration effect/Tons refrigeration effect |
| D. | All of the above |
| Answer» B. kW Input/Tons refrigeration effect | |
| 21. |
A cold storage is to be maintained at –5°C while the surroundings are at 35°C. The heat leakage from the surroundings into the cold storage is estimated to be 29 kW. The actual COP of the refrigeration plant used is \(\frac{1}{3}rd\) that of an ideal plant working between the same temperatures. The power required to drive the plant will be |
| A. | 13 kW |
| B. | 14 kW |
| C. | 15 kW |
| D. | 16 kW |
| Answer» B. 14 kW | |
| 22. |
In a vapour compression refrigeration system, if liquid heat at temperature ‘T1’ and ‘T2’ are 100 kJ/kg and 25 kJ/kg respectively and the dryness fraction at ‘a’ is 0.5, find Latent Heat of refrigerant. |
| A. | 200 kJ/kg |
| B. | 300 kJ/kg |
| C. | 150 kJ/kg |
| D. | 350 kJ/kg |
| Answer» D. 350 kJ/kg | |
| 23. |
A refrigeration system works on |
| A. | Second law of thermodynamics |
| B. | First law of thermodynamics |
| C. | Zeroth law of thermodynamics |
| D. | None of the above |
| Answer» B. First law of thermodynamics | |
| 24. |
_____ use(s) air refrigeration cycle. |
| A. | Cryogenic chambers |
| B. | Aircraft air-conditioning system |
| C. | Gas chambers |
| D. | Commercial refrigeration |
| Answer» C. Gas chambers | |
| 25. |
Electrolux system of refrigerant has: |
| A. | Only one liquid pump |
| B. | Only three liquid pump |
| C. | No liquid pump |
| D. | Only two liquid pump |
| Answer» D. Only two liquid pump | |
| 26. |
At constant condenser pressure, reduction in evaporator pressure of vapour compression refrigeration cycle does not lead to: |
| A. | Increase in specific volume of suction vapour |
| B. | Decrease in refrigeration effect |
| C. | Decrease in specific compressor work |
| D. | Decrease in evaporation temperature |
| Answer» D. Decrease in evaporation temperature | |
| 27. |
A vapour compression refrigeration cycle with subcooling is shown in the figure along with refrigerant enthalpy data. The specific heat of the liquid refrigerant is 5 kJ/kg-K. What is the coefficient of performance of the cycle? |
| A. | 5.4 |
| B. | 3.8 |
| C. | 2.9 |
| D. | 4.15 |
| Answer» E. | |
| 28. |
A reversed Carnot engine is used for heating a building. It supplies 210 × 103 kJ/hr of heat to the building at 20°C. The outside air is at –5°C. The heat taken from the outside will be nearly |
| A. | 192 × 103 kJ/hr |
| B. | 188 × 103 kJ/hr |
| C. | 184 × 103 kJ/hr |
| D. | 180 × 103 kJ/hr |
| Answer» B. 188 × 103 kJ/hr | |
| 29. |
A refrigerator that operates on a Carnot cycle is required to transfer 2000 kJ/min to the atmosphere at 27°C, where the low temperature reservoir is at 0°C, What is the power required? |
| A. | 200 W |
| B. | 32.93 kW |
| C. | 200 kW |
| D. | 3.33 kW |
| Answer» E. | |
| 30. |
Domestic Refrigerator are specified by : |
| A. | cool space volume |
| B. | heat transfer rate alone |
| C. | color of front panel |
| D. | none of the above |
| Answer» B. heat transfer rate alone | |
| 31. |
In vapour absorption refrigeration systems, which of the following fluids are commonly used? |
| A. | Air and water |
| B. | Sulphur dioxide and water |
| C. | Ammonia and water |
| D. | Freon and water |
| Answer» D. Freon and water | |
| 32. |
A domestic refrigerator works on the: |
| A. | air refrigeration cycle |
| B. | Vapour compression refrigeration cycle |
| C. | Steam jet refrigeration cycle |
| D. | Vapour absorption refrigeration cycle |
| Answer» C. Steam jet refrigeration cycle | |
| 33. |
In compound compression refrigeration system with intercooling, the intermediate pressure p2, if the cooling system is fixed, is given by(p1 = Suction or evaporator pressure, p3 = Condensers pressure) |
| A. | p2 = p1/p3 |
| B. | p2 = p3/p1 |
| C. | p2 = p1 × p3 |
| D. | \({p_2} = \sqrt {{p_1} \times {p_3}} \) |
| Answer» E. | |
| 34. |
A refrigerator cycle operates between condenser temperature of + 27° C and evaporator temperature of – 23°C. The C.O.P of the cycle is |
| A. | 0.2 |
| B. | 1.2 |
| C. | 5 |
| D. | 6 |
| Answer» D. 6 | |
| 35. |
A solar collector receiving solar radiation at the rate of 0.6 kW/m2 transforms it to the internal energy of a fluid at an overall efficiency of 50%. The fluid heated to 350 K is used to run a heat engine which rejects heat at 313 K. If the heat engine is to deliver 2.5 kW power, the minimum area of the solar collector required would be |
| A. | 8.33 m2 |
| B. | 16.66 m2 |
| C. | 39.68 m2 |
| D. | 79.36 m2 |
| Answer» E. | |
| 36. |
1 ton of refrigerant is |
| A. | the SI unit used in refrigeration problem |
| B. | the cooling effect produced by melting 1 ton of ice |
| C. | the refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hrs. |
| D. | the refrigeration effect to produce 1 ton of ice at NTP condition |
| Answer» D. the refrigeration effect to produce 1 ton of ice at NTP condition | |
| 37. |
As the condenser temperature increases, the compressor power consumption |
| A. | Decreases |
| B. | Increases |
| C. | Remains constant |
| D. | None of the above |
| Answer» C. Remains constant | |
| 38. |
One tonne refrigeration machine means: |
| A. | One tonne of ice melts from 0°C in 24 hours |
| B. | Mass of the machine |
| C. | One tonne of water is converted into ice |
| D. | One tonne of refrigerant is used |
| Answer» B. Mass of the machine | |
| 39. |
In a refrigeration plant, in a direct expansion evaporator: |
| A. | The liquid refrigerant evaporates outside the tubes in a shell and tube heat exchanger |
| B. | There is no need for a throttling device |
| C. | The refrigerant evaporates in a finned coil, which cools air or liquid flowing across it |
| D. | There is a coil with smooth surface inside for refrigerant evaporation |
| Answer» D. There is a coil with smooth surface inside for refrigerant evaporation | |
| 40. |
Commercial ice plants work on ___________. |
| A. | Vortex tube |
| B. | Vapour compression cycle |
| C. | Pulse tube refrigeration |
| D. | Vapour absorption cycle |
| Answer» C. Pulse tube refrigeration | |
| 41. |
If the evaporator temperature of a plant is lowered keeping the ‘condenser temp. constant, the power input of compressor required will be |
| A. | same |
| B. | more |
| C. | less |
| D. | unpredictable |
| Answer» C. less | |
| 42. |
A cycle consisting of two isothermal and two isentropic processes is known as |
| A. | Stirling cycle |
| B. | Carnot cycle |
| C. | Ericsson cycle |
| D. | Joule cycle |
| Answer» C. Ericsson cycle | |
| 43. |
__________ is used as refrigerant in a vapour absorption refrigerator. |
| A. | Aqua ammonia |
| B. | Freon |
| C. | Water |
| D. | Sulphur dioxide |
| Answer» B. Freon | |
| 44. |
A hermetically sealed unit implies ____. |
| A. | Compressor is sealed |
| B. | Compressor motor is sealed |
| C. | Refrigerant cycle sealed |
| D. | Compressor and motor are sealed |
| Answer» E. | |
| 45. |
In a split unit of an air-conditioner, which of the following components is placed in the outdoor unit? |
| A. | Evaporation unit |
| B. | Compressor and condenser |
| C. | Capillary tube |
| D. | Air filter |
| Answer» C. Capillary tube | |
| 46. |
One ton of refrigeration is equivalent to SI unit of |
| A. | 1 kW |
| B. | 2.5 kW |
| C. | 3.5 kW |
| D. | 5 kW |
| Answer» D. 5 kW | |
| 47. |
For a refrigerating machine, capacity is expressed as ______. |
| A. | rate of heat extraction from the space being cooled |
| B. | gross weight of the machine |
| C. | inside volume of the cabinet |
| D. | the lowest temperature attained |
| Answer» B. gross weight of the machine | |
| 48. |
A refrigerator working on a reversed Carnot cycle has a COP of 4. If it works as a heat pump and consumes 1 kW, the heating effect will be |
| A. | 1 kW |
| B. | 4 kW |
| C. | 5 kW |
| D. | 6 kW |
| Answer» D. 6 kW | |
| 49. |
1 ton of refrigeration is equal to: |
| A. | 620 kJ/min |
| B. | 21 kJ/min |
| C. | 420 kJ/min |
| D. | 210 kJ/min |
| Answer» E. | |
| 50. |
A condenser of a refrigeration system rejects heat at rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system would be |
| A. | ¼ |
| B. | 1/3 |
| C. | 3 |
| D. | 4 |
| Answer» D. 4 | |