MCQOPTIONS
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MCQOPTIONS
This section includes 205 Mcqs, each offering curated multiple-choice questions to sharpen your Refrigeration and Air conditioning knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
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» B. It is less efficient | |
| 52. |
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» E. None of the above | |
| 53. |
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» C. Below which a gas does not obey gas laws | |
| 54. |
One tonne of refrigeration is equivalent to SI units of |
| A. | 3.5 kW |
| B. | 10 kW |
| C. | 5 kW |
| D. | 1 kW |
| E. | 2.5 kW |
| Answer» B. 10 kW | |
| 55. |
Dew point is |
| A. | The temperature at which ice starts melting in presence of air without external aid |
| B. | Percentage of moisture contained in a sample of air |
| C. | The temperature of water vapour in air starts |
| D. | Partial pressure of water vapour in a sample of air |
| E. | The temperature at which condensation of water vapour in air starts |
| Answer» F. | |
| 56. |
In case air is cooled by a process in which the humidity ratio of air does not change, the process is known as |
| A. | Ventilation |
| B. | Humidification |
| C. | Chilling |
| D. | Sensible cooling |
| E. | Dehumidification |
| Answer» E. Dehumidification | |
| 57. |
The ratio of water vapour to the mass of dry air in a given mixture is known as |
| A. | Humidity ratio |
| B. | Relative humidity |
| C. | Degree of saturation |
| D. | Any of the above |
| E. | None of the above |
| Answer» B. Relative humidity | |
| 58. |
Presence of moisture in a refrigeration cycle will show its effect at |
| A. | Compressor suction |
| B. | Compressor discharge |
| C. | Expansion valve |
| D. | Condenser |
| E. | All of the above |
| Answer» D. Condenser | |
| 59. |
When air is adiabatically saturated, the temperature attained is known as |
| A. | Dew point temp |
| B. | Dry bulb temp |
| C. | Adiabatically sturated temp |
| D. | Wet bulb temp |
| E. | Critical temp |
| Answer» E. Critical temp | |
| 60. |
When ammonia is used as a refrigerant in vapour compression cycle, the mass circulated per ton of refrigerating effect will be nearly |
| A. | 0.2 kg |
| B. | 1 kg |
| C. | 1.2 kg |
| D. | 0.5 kg |
| E. | 1.8 kg |
| Answer» B. 1 kg | |
| 61. |
If a room has bad ammonia leaks |
| A. | Lights should be switched off |
| B. | No specific precautions are needed |
| C. | One should wait for sometime |
| D. | Gas mask should be put on |
| E. | Before entering the room fans should be put on |
| Answer» E. Before entering the room fans should be put on | |
| 62. |
Cryogenics |
| A. | Is same as refrigeration |
| B. | Include heating and cooling of liquids |
| C. | Is a thermodynamic analysis of low temperature systems |
| D. | Is the field of engineering associated with development, production and use of equipment in the range -180?C to absolute zero |
| E. | None of the above |
| Answer» E. None of the above | |
| 63. |
Which of the following refrigerant is highly toxic? |
| A. | Freon 12 |
| B. | Carbondioxide |
| C. | Ammonia |
| D. | Freon 22 |
| E. | Sulphurdioxide |
| Answer» F. | |
| 64. |
Which of the following refrigerant is the cheapest? |
| A. | Air |
| B. | Ammonia |
| C. | Methyl chloride |
| D. | Freon 12 |
| E. | Freon 22 |
| Answer» B. Ammonia | |
| 65. |
If the compressor of a refrigeration system is noisy, it shows that |
| A. | Compressor drive coupling is loose |
| B. | Lack of oil |
| C. | Internal parts of compressor broken |
| D. | Compressor or motor loose on base |
| E. | Any of the above |
| Answer» F. | |
| 66. |
The moisture in a refrigeration system is removed by |
| A. | Driers |
| B. | Dehumidifiers |
| C. | Evaporators |
| D. | Coolers |
| E. | None of the above |
| Answer» B. Dehumidifiers | |
| 67. |
Which type of compressor is commonly used in room air-conditioner |
| A. | Reciprocating |
| B. | Rotory |
| C. | Screw |
| D. | Centrifugal |
| E. | None of the above |
| Answer» B. Rotory | |
| 68. |
The freezing point of ammonia is |
| A. | ? 132.5?C |
| B. | ? 20?C |
| C. | ? 77.8?C |
| D. | ? 202.5?C |
| E. | 0?C |
| Answer» D. ? 202.5?C | |
| 69. |
For for measurement of temperature in cryogenic range the thermometers used are |
| A. | Gas thermometers |
| B. | Electronic digital instruments |
| C. | Mercury thermometers |
| D. | Pyrometers |
| E. | Radiation pyrometers |
| Answer» B. Electronic digital instruments | |
| 70. |
A refrigerant with lowest freezing point temperature is |
| A. | Ammonia |
| B. | Freon 12 |
| C. | Freon 22 |
| D. | Carbondioxide |
| E. | Freon 11 |
| Answer» D. Carbondioxide | |
| 71. |
If the condensation temperature of a refrigerant is 25?C which type of condenser cannot be used? |
| A. | Air cooled condenser |
| B. | Water cooled condenser |
| C. | Brine circulation condenser |
| D. | Ice cooled condenser |
| E. | Any of the above |
| Answer» B. Water cooled condenser | |
| 72. |
Sub-cooling is |
| A. | Removing sensible heat from a liquid |
| B. | Removing latent heat from a gas |
| C. | Cooling a liquid below 0?C. |
| D. | Cooling a part of liquid |
| E. | Differential cooling of a liquid |
| Answer» E. Differential cooling of a liquid | |
| 73. |
"The difference between the length of a certain brass rod and that of a steel rod is clamped to be constant at all temperatures". The above statement |
| A. | can never be true |
| B. | can be valid only for temperatures below 0?C |
| C. | can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod |
| D. | can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod |
| E. | None of the above |
| Answer» E. None of the above | |
| 74. |
The type of compressor used in refrigeration system is |
| A. | Reciprocating |
| B. | Centrifugal |
| C. | Rotary sliding vane |
| D. | Rotary screw compressor |
| E. | All of the above |
| Answer» F. | |
| 75. |
If space occupied by the refrigerating plant and cost is the major consideration, which of the following refrigerant will be preferred? |
| A. | Carbondioxide |
| B. | Sulphur dioxide |
| C. | Mehtyl chloride |
| D. | Ammonia |
| E. | Any of the above |
| Answer» B. Sulphur dioxide | |
| 76. |
A Carnot refrigerator operates between 300.3 K and 273 K. The fraction of cooling effect required as work input is |
| A. | 20% |
| B. | 10% |
| C. | 50% |
| D. | Not possible to find with the data |
| E. | All of the above |
| Answer» C. 50% | |
| 77. |
The heat removed capacity of a one ton refrigerator is |
| A. | 100 kcal/4 hour |
| B. | 100 kcal/hour |
| C. | 50 kcal/min |
| D. | 25 kcal/sec |
| E. | None of the above |
| Answer» D. 25 kcal/sec | |
| 78. |
2 HP per ton of refrigeration is required to maintain the temperature of - 40?C in the refrigerator if the refrigeration cycle works on Carnot cycle. The COP of the cycle would be |
| A. | 0.4 |
| B. | 1 |
| C. | 2.38 |
| D. | 5 |
| E. | 4.76 |
| Answer» D. 5 | |
| 79. |
A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at - 15?C and it is discharged to atmosphere 30C?. The horse power required to run the unit would be |
| A. | More than 6 |
| B. | 2 to 5 |
| C. | 5 to 6 |
| D. | 1.5 to 2 |
| E. | 1 |
| Answer» E. 1 | |
| 80. |
During sensible of cooling of air |
| A. | Wet bulb temperature decreases and relative humidity increases |
| B. | Both wet bulb temperatures as well as relative humidity increase |
| C. | Both humidity ratio as well as relative humidity remain constant |
| D. | Both wet bulb temperature as well as relative humidity decrease |
| E. | Wet bulb temperatures increases and relative humidity decreases |
| Answer» B. Both wet bulb temperatures as well as relative humidity increase | |
| 81. |
Brazing is the process used for joining |
| A. | Two ferrous materials |
| B. | One ferrous and one non-ferrous material |
| C. | Two non-ferrous materials |
| D. | Two non-metals |
| E. | None of the above |
| Answer» D. Two non-metals | |
| 82. |
Which reciprocating compressor is usually used in domestic refrigerators? |
| A. | Open type |
| B. | Semi-sealed type |
| C. | Hermetically sealed type |
| D. | Any of the above |
| E. | None of the above |
| Answer» D. Any of the above | |
| 83. |
In a refrigeration cycle the heat is rejected by refrigerant at |
| A. | Evaporator |
| B. | Condenser |
| C. | Expansion valve |
| D. | Compressor |
| E. | All of the above |
| Answer» C. Expansion valve | |
| 84. |
A prssure gauge on the discharge side of compressor |
| A. | Is mounted for show only |
| B. | Indicates the temperature of refrigerant after compression |
| C. | Gives a warning when the pressure reaches a dangerous point |
| D. | Gives an ideas about the coefficient of performance of the cycle |
| E. | Confirms the flow of refrigerant in cycle |
| Answer» D. Gives an ideas about the coefficient of performance of the cycle | |
| 85. |
An average adult while sitting in a cinema hall |
| A. | Discharges about 100 kcal of heat per hour |
| B. | Discards about 500 kcal of heat per hour |
| C. | Absorbs about 500 kcal of heat per hour |
| D. | Neither absorbs nor discards heat |
| E. | Absorbs about 100 kcal of heat per hour |
| Answer» B. Discards about 500 kcal of heat per hour | |
| 86. |
In ammonia vapour compression system the temperature rise between the condenser outlet and the expansion valve should be |
| A. | As high as possible to improve the performance |
| B. | As high as possible to reduce motor power inputs |
| C. | As little as possible for better performance |
| D. | Anything as it has no bearing on the performance of system |
| E. | None of the above |
| Answer» D. Anything as it has no bearing on the performance of system | |
| 87. |
Which of the following connections is usually not provided in a hermetically sealed type compressors? |
| A. | Refrigerant inlet |
| B. | Refrigerant outlet |
| C. | Refrigerant charging connection |
| D. | Lubricating oil charging connection |
| E. | There is no connection provided |
| Answer» E. There is no connection provided | |
| 88. |
A thermometer in the compressor discharge line |
| A. | Confirms the flow of refrigerant |
| B. | Indicates the efficiency of cycle |
| C. | Helps in adjusting the compressor performance |
| D. | Shows the heat of refrigerant leaving the cylinder on way to the condenser |
| E. | None of the above |
| Answer» E. None of the above | |
| 89. |
In a refrigerator system if compressor fails to operate, the probable reason could be |
| A. | Power failure |
| B. | Low voltage |
| C. | Burnt motor |
| D. | Fuse blown |
| E. | Any of the above |
| Answer» F. | |
| 90. |
The ratio of mass of water vapour associated with unit mass of dry air to the mass of water vapour associated with unit mass of dry air saturated at the same temperature is known as |
| A. | Relative humidity |
| B. | Specific humidity decreases |
| C. | Humidity ratio |
| D. | Degree of saturation |
| E. | None of the above |
| Answer» E. None of the above | |
| 91. |
White ice is |
| A. | Sub-cooled water |
| B. | Fast cooled water |
| C. | Due to dissolved air, gases and impurities |
| D. | Produced by blowing air during freezing |
| E. | None of the above |
| Answer» D. Produced by blowing air during freezing | |
| 92. |
In order to ensure leak proof mechanical links, the end of copper tubing in refrigeration cycle is |
| A. | Flared |
| B. | Brazed |
| C. | Soldered |
| D. | Press-fitted |
| E. | (C) and (D) together |
| Answer» B. Brazed | |
| 93. |
When moisture is added to air at constant dry bulb temperature, the process is known as |
| A. | Humidification |
| B. | Sensible cooling |
| C. | Wetting |
| D. | Chilling |
| E. | None of the above |
| Answer» B. Sensible cooling | |
| 94. |
Dew points temperature is an indication of |
| A. | Moisture content of air |
| B. | Dryness of air |
| C. | Lowest temperature where air and water vapour start separating |
| D. | Condition air |
| E. | Any of the above |
| Answer» B. Dryness of air | |
| 95. |
In vapour absorption system the function of rectifier is |
| A. | To cool the vapour leaving the analyzer |
| B. | To separate ammonia and water |
| C. | To dissolve ammonia in water |
| D. | To add energy from external source |
| E. | None of the above |
| Answer» B. To separate ammonia and water | |
| 96. |
On a particular time of a day if dry bulb temperature is equal to the wet bulb temperature, then it can be safely concluded that |
| A. | Dew point was less than 20?C |
| B. | Rain had occurred one or two hours earlier |
| C. | Relative humidity of air was 100% |
| D. | Specific humidity of air was 0.010 kg per kg of dry air |
| E. | Atmospheric air was free from moisture |
| Answer» D. Specific humidity of air was 0.010 kg per kg of dry air | |
| 97. |
In which of the following plants secondary refrigerant is used? |
| A. | Domestic refrigerator |
| B. | Room air conditioner |
| C. | Deep freezer |
| D. | Ice plant |
| E. | None of the above |
| Answer» E. None of the above | |
| 98. |
Of the following chemicals the liquid having the greatest cooling effect on an individual is |
| A. | Water |
| B. | Water containing ammonium hydroxide |
| C. | Ether |
| D. | Alcohol |
| E. | Brine |
| Answer» E. Brine | |
| 99. |
The most common type of vapour absorption system in use for industrial application is |
| A. | Hydrogen and water |
| B. | Freon 22 and water |
| C. | Brine and water |
| D. | Freon 12 and water |
| E. | Ammonia and water |
| Answer» F. | |
| 100. |
A thermometer in vapour compression system is installed in the main line close to the compressor |
| A. | As it helps the operator to adjust compressor for greatest efficiency |
| B. | As temperature indicates whether liquid or vapour refrigerant is going to compressor |
| C. | As temperature helps in calculating the coefficient of performance |
| D. | As the performance of other units of the cycle can be controlled |
| E. | None of the above |
| Answer» B. As temperature indicates whether liquid or vapour refrigerant is going to compressor | |