McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
Chapters
| 1. |
Reversed carnot cycle comprises |
| A. | two isentropic processes and two adiabatic processes |
| B. | two isentropic processes and two isothermal processes |
| C. | two isentropic processes and two isobaric processes |
| D. | two isentropic processes and two isochoric processes |
| Answer» B. two isentropic processes and two isothermal processes | |
| 2. |
Two Carnot Refrigerators are employed, one for ice making and other for comfort cooling |
| A. | The COP of the refrigerator for ice making is higher than that for other |
| B. | The COP of the refrigerator for ice making is same as that for the other |
| C. | The COP of the refrigerator for ice making is lower than that for other |
| D. | The COP of Carnot refrigerator will depend on refrigerant used |
| Answer» C. The COP of the refrigerator for ice making is lower than that for other | |
| 3. |
A reversed Carnot cycle has a COP of 4. The ratio of higher temperature to lower temperature will be |
| A. | 1.25 |
| B. | 1.5 |
| C. | 2 |
| D. | 2.5 |
| Answer» A. 1.25 | |
| 4. |
Carnot refrigerator absorbs heat at -13° C and requires 1 kW for each 6.5 kW of heat absorbed, the COP and temperature of heat rejections respectively |
| A. | COP = 6.5, t = 27° C |
| B. | COP = 7.5, t = 27° C |
| C. | COP = 6.5, t = 30° C |
| D. | COP = 7.5, t = 37° C |
| Answer» A. COP = 6.5, t = 27° C | |
| 5. |
The dense air refrigeration system as compared to open air refrigeration system for same range of temperatures using Bell- Colemann cycle requires. |
| A. | Same power/Ton of Refrigeration |
| B. | Lower power/Ton of Refrigeration |
| C. | Higher power/Ton of Refrigeration |
| D. | Unpredictable Results. |
| Answer» B. Lower power/Ton of Refrigeration | |
| 6. |
For very high speed planes cruising at Mach number 2.5 and above, the air craft refrigeration system recommended is |
| A. | Simple evaporative type |
| B. | Boot-strap type |
| C. | Regenerative type |
| D. | Boot strap evaporative type |
| Answer» D. Boot strap evaporative type | |
| 7. |
The air craft system giving Lowest Dry Air Rated Turbine discharge temperature at supersonic cruising speeds of the plane, is |
| A. | Reduced ambient system of Refrigeration |
| B. | Boot-strap system of Refrigeration |
| C. | Regenerative system of Refrigeration |
| D. | Boot strap evaporative system of Refrigeration |
| Answer» D. Boot strap evaporative system of Refrigeration | |
| 8. |
There are two cooling turbines in |
| A. | Reduced ambient system of Refrigeration |
| B. | Boot-strap system of Refrigeration |
| C. | Regenerative system of Refrigeration |
| D. | Boot strap evaporative system of Refrigeration |
| Answer» A. Reduced ambient system of Refrigeration | |
| 9. |
There are two stages of compression of air in |
| A. | Reduced ambient system of Refrigeration |
| B. | Boot-strap system of Refrigeration |
| C. | Regenerative system of Refrigeration |
| D. | Simple evaporative system of Refrigeration |
| Answer» B. Boot-strap system of Refrigeration | |
| 10. |
The amount of heat absorbed by the system at low temperature is |
| A. | COP |
| B. | Refrigerating effect |
| C. | work done on the system |
| D. | refrigeration efficiency |
| Answer» B. Refrigerating effect | |
| 11. |
No refrigerator using reversed Carnot cycle has been constructed because |
| A. | it is less efficient |
| B. | it is uneconomical |
| C. | isentropic portions of cycle require low speeds where as isothermal portions require high speeds |
| D. | isentropic portions of cycle require high speeds where as isothermal portions require low speeds |
| Answer» D. isentropic portions of cycle require high speeds where as isothermal portions require low speeds | |
| 12. |
A refrigeration cycle is usually a |
| A. | open cycle |
| B. | closed cycle |
| C. | mixed cycle |
| D. | Hybrid cycle |
| Answer» B. closed cycle | |
| 13. |
Co-efficient of performance of a Reversed Carnot cycle refrigerator working between higher temperature T2 and lower temperature T1 |
| A. | will increase with increase in T1 keeping T2 fixed |
| B. | will decrease with increase in T1 keeping T2 fixed |
| C. | will first increase with increase in T1 and then decrease with increase T1 keeping T2 fixed |
| D. | None of the above |
| Answer» A. will increase with increase in T1 keeping T2 fixed | |
| 14. |
Bell-Colemann cycle comprises |
| A. | two isentropic processes and two adiabatic processes |
| B. | two isentropic processes and two isothermal processes |
| C. | two isentropic processes and two isobaric processes |
| D. | two isentropic processes and two isochoric processes |
| Answer» C. two isentropic processes and two isobaric processes | |
| 15. |
The COP of Carnot Refrigerator is 3 and it produces 1 TR. The work that will be done is equal to |
| A. | 70 kJ/min |
| B. | 100 kJ/min |
| C. | 200 kJ/min |
| D. | 210 kJ/min |
| Answer» A. 70 kJ/min | |
| 16. |
In Bell – Colemann refrigerator for the same temperature range |
| A. | COP of dense air system is equal to COP of open air system |
| B. | COP of dense air system is lower than COP of open air system |
| C. | COP of dense air system is higher than COP of open air system |
| D. | COP of dense air system may be higher or lower than COP of open air system depending upon pressure ratio. |
| Answer» C. COP of dense air system is higher than COP of open air system | |
| 17. |
The air craft system giving Lowest Dry Air Rated Turbine discharge temperature at supersonic cruising speeds of the plane, is |
| A. | Reduced ambient system of Refrigeration |
| B. | Boot-strap system of Refrigeration |
| C. | Regenerative system of Refrigeration |
| D. | Boot strap evaporative system of Refrigeration |
| Answer» D. Boot strap evaporative system of Refrigeration | |
| 18. |
A Bell-Colemann cycle is |
| A. | reversed Carnot Cycle |
| B. | reversed Joule Cycle |
| C. | reversed Rankine cycle |
| D. | None of the above |
| Answer» B. reversed Joule Cycle | |
| 19. |
In a refrigeration cycle the heat is rejected by refrigerant at |
| A. | expansion valve |
| B. | compressor |
| C. | condenser |
| D. | all the above |
| Answer» C. condenser | |
| 20. |
A reversible refrigerator working between two fixed temperatures |
| A. | has the same COP whatever the working substance |
| B. | has its COP increased for working substance with high enthalpy of evaporation |
| C. | has its COP increased for working substance with higher specific heats |
| D. | none of the above |
| Answer» A. has the same COP whatever the working substance | |
| 21. |
A reversible refrigerator working between two fixed temperatures |
| A. | has the same COP whatever the working substance |
| B. | has its COP increased for working substance with high enthalpy of evaporation |
| C. | has its COP increased for working substance with higher specific heats |
| D. | none of above |
| Answer» A. has the same COP whatever the working substance | |
| 22. |
Heat is absorbed by the refrigerant, during vapour compression refrigeration cycle in |
| A. | Compressor |
| B. | Condenser |
| C. | Evaporator |
| D. | Throttle valve |
| Answer» C. Evaporator | |
| 23. |
In a simple saturated vapour compression cycle, the refrigerant is in superheated condition |
| A. | before entering compressor |
| B. | before entering condenser |
| C. | before entering throttle valve |
| D. | before entering evaporator |
| Answer» B. before entering condenser | |
| 24. |
Sub-cooling is a process of cooling the refrigerant in vapour compression refrigeration system |
| A. | after compression |
| B. | before compression |
| C. | before Throttling |
| D. | none of the above |
| Answer» C. before Throttling | |
| 25. |
The order in which main components of vapour compression refrigeration system are used is |
| A. | compressor-evaporator-condenser-throttle valve |
| B. | compressor-condenser-evaporator-throttle valve |
| C. | compressor-throttle valve- evaporator-condenser |
| D. | compressor-condenser- throttle valve- evaporator |
| Answer» D. compressor-condenser- throttle valve- evaporator | |
| 26. |
The oil separator is incorporated in vapour compression refrigeration system |
| A. | between evaporator and compressor |
| B. | between compressor and condenser |
| C. | between condenser and Throttle valve |
| D. | between throttle valve and evaporator |
| Answer» B. between compressor and condenser | |
| 27. |
In vapour compression refrigeration cycle the following data is available Heat rejected in condenser = 65 KW Work done in compressor = 10 kw, then COP( refrigerator) is |
| A. | 4.5 |
| B. | 5.5 |
| C. | 6.5 |
| D. | not possible to find with the given data |
| Answer» B. 5.5 | |
| 28. |
Following results are tabulated for vapour compression refrigeration cycle.
|
| A. | 3.5 |
| B. | 4.5 |
| C. | 5.5 |
| D. | 6.5 |
| Answer» C. 5.5 | |
| 29. |
For simple saturated vapour compression refrigeration cycle operating between 5°C and 40°C, and the refrigerants being R-11, R-12, R-717 and R-22, the evaporator pressure is lowest for |
| A. | R-11 |
| B. | R-12 |
| C. | R-717 |
| D. | R-22 |
| Answer» A. R-11 | |
| 30. |
For simple saturated vapour compression refrigeration cycle operating between 5°C and 40°C, and the refrigerants being R-11, R-12, R-717 and R-22, the compressor displacement per min per ton of refrigeration is highest for |
| A. | R-11 |
| B. | R-12 |
| C. | R-717 |
| D. | R-22 |
| Answer» A. R-11 | |
| 31. |
With reciprocating compressor in vapour compression refrigeration system, wetcompression is not desirable because |
| A. | liquid trapped up in the head of cylinder may damage the compressor valves |
| B. | COP of the cycle decreases |
| C. | volumetric efficiency of compressor decreases |
| D. | mass flow rate per ton of refrigerant increases |
| Answer» A. liquid trapped up in the head of cylinder may damage the compressor valves | |
| 32. |
An ideal refrigerant should have |
| A. | low latent heat of vaporization |
| B. | high critical temperature |
| C. | high boiling point |
| D. | high specific volume of vapour |
| Answer» B. high critical temperature | |
| 33. |
The refrigerant leaving throttle valve is |
| A. | saturated liquid |
| B. | saturated vapour |
| C. | superheated vapour |
| D. | fraction as saturated vapour and remainder as liquid |
| Answer» D. fraction as saturated vapour and remainder as liquid | |
| 34. |
Freon group of refrigerants |
| A. | toxic |
| B. | inflammable |
| C. | non-toxic and non-inflammable |
| D. | highly toxic and inflammable |
| Answer» C. non-toxic and non-inflammable | |
| 35. |
The leaks of refrigerant from a cycle may be detected by |
| A. | halide torch test |
| B. | sulphur candle test |
| C. | soap and water test |
| D. | any of the above |
| Answer» D. any of the above | |
| 36. |
During compression in a vapour compression cycle the refrigerant is super heated |
| A. | work done is increased |
| B. | C.O.P is increased |
| C. | Work done is reduced |
| D. | Refrigerating effect is reduced |
| Answer» A. work done is increased | |
| 37. |
Heat is rejected by the refrigerant, during vapour compression refrigeration cycle in |
| A. | Compressor |
| B. | Condenser |
| C. | Evaporator |
| D. | Throttle valve |
| Answer» B. Condenser | |
| 38. |
Wet compression vapour compression refrigeration cycle means |
| A. | Vapour compression takes place in wet region |
| B. | Vapour compression in dry region, but evaporation in wet region |
| C. | vapour compression in wet region, but leaves in superheated region |
| D. | None of the above |
| Answer» A. Vapour compression takes place in wet region | |
| 39. |
For simple saturated vapour compression refrigeration cycle operating between 5°C and 40°C, and the refrigerants being R-11, R-12, R-717 and R-22, the evaporator pressure is highest for |
| A. | R-11 |
| B. | R-12 |
| C. | R-717 |
| D. | R-22 |
| Answer» D. R-22 | |
| 40. |
With reciprocating compressor in vapour compression refrigeration system, wet compression is not desirable because |
| A. | liquid trapped up in the head of cylinder may damage the compressor valves |
| B. | COP of the cycle decreases |
| C. | volumetric efficiency of compressor decreases |
| D. | mass flow rate per ton of refrigerant increases |
| Answer» A. liquid trapped up in the head of cylinder may damage the compressor valves | |
| 41. |
An ideal refrigerant should have |
| A. | low latent heat of vaporization |
| B. | lower critical temperature |
| C. | lower boiling point |
| D. | high specific volume of vapour |
| Answer» C. lower boiling point | |
| 42. |
During compression in a vapour compression cycle the refrigerant is super heated |
| A. | C.O.P is reduced |
| B. | C.O.P is increased |
| C. | Work done is reduced |
| D. | Refrigerating effect is reduced |
| Answer» A. C.O.P is reduced | |
| 43. |
Heat is absorbed by a refrigerant, during a refrigeration cycle in a |
| A. | condenser |
| B. | evaporator |
| C. | compressor |
| D. | throttle valve |
| Answer» B. evaporator | |
| 44. |
What is the effect of frost on the cooling coils of the evaporator of refrigeration system |
| A. | It reduces the life of cooling coils |
| B. | It increases the compressor pressure |
| C. | It makes the compressor run for comparatively short runs |
| D. | It acts as the insulator and decreases the heat transfer rate |
| Answer» D. It acts as the insulator and decreases the heat transfer rate | |
| 45. |
The widely used refrigerant in domestic refrigerators is |
| A. | Carbon-dioxide |
| B. | Sulphur dioxide |
| C. | Freon-12 |
| D. | Ammonia |
| Answer» C. Freon-12 | |
| 46. |
Freon group refrigerants are |
| A. | toxic |
| B. | inflamma |
| C. | nontoxic and inflammable |
| D. | non- toxic & non-inflammable |
| Answer» D. non- toxic & non-inflammable | |
| 47. |
Latent heat of vaporization of a refrigerant ,at lower temperatures and pressures |
| A. | increase |
| B. | decreases |
| C. | remains constant |
| D. | unpredictable |
| Answer» A. increase | |
| 48. |
The refrigerant with highest critical pressure is |
| A. | Carbon dioxide |
| B. | Ammonia |
| C. | Freon-11 |
| D. | Freon-22 |
| Answer» B. Ammonia | |
| 49. |
The Refrigerant commonly used in commercial ice plants is |
| A. | Carbon-dioxide |
| B. | Air |
| C. | Ammonia |
| D. | Freon-12 |
| Answer» C. Ammonia | |
| 50. |
Which of the following refrigerants has the lowest boiling point? |
| A. | Freon-12 |
| B. | Carbon-dioxide |
| C. | Ammonia |
| D. | Sulphur dioxide |
| Answer» B. Carbon-dioxide | |
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