MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 346 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Consider the following statements with regard to air-conditioning systems:1. In adiabatic saturation process, air-vapour mixture undergoes a process of constant relative humidity2. Wet bulb temperature of air whose relative humidity is 100 is equal to the dew point temperature3. In winter air conditioning, the process is heating and humidification4. For designing air conditioning ducts, equal friction method automatically reduces the air velocity in the duct in the direction of flowWhich of the above statements are correct? |
| A. | 1 and 2 |
| B. | 1 and 4 |
| C. | 2 and 3 |
| D. | 3 and 4 |
| Answer» D. 3 and 4 | |
| 52. |
Atmospheric air at a dry bulb temperature of 15°C enters a heating coil whose surface temperature is maintained at 40°C. The air leaves the heating coil at 25°C. What will be the by-pass factor of the heating coil? |
| A. | 0.376 |
| B. | 0.4 |
| C. | 0.6 |
| D. | 0.67 |
| Answer» D. 0.67 | |
| 53. |
If air is heated without changing its moisture content, the dew point will _____. |
| A. | Increase |
| B. | Decrease |
| C. | Remain the same |
| D. | Unpredictable |
| Answer» D. Unpredictable | |
| 54. |
Air is passed through a cooling coil at a temperature of – 5°C. If the temperature of air drops from 25°C to 10°C, the Bypass factor of the coil is |
| A. | 0.2 |
| B. | 0.5 |
| C. | 0.7 |
| D. | 1 |
| Answer» C. 0.7 | |
| 55. |
In an air-handling unit, air enters the cooling coil at a temperature of 30 °C. The surface temperature of the coil is –10 °C. If the bypass factor of the coil is 0.45, then the temperature of the air at the exit will be |
| A. | 6 °C |
| B. | 8 °C |
| C. | 10 °C |
| D. | 12 °C |
| Answer» C. 10 °C | |
| 56. |
A liquid is boiling in a airtight vessel. Using an exhaust tube the vapour is pumped out at a faster rate. What will happen to the liquid? |
| A. | Temperature will go down but boiling will continue |
| B. | Temperature will rise and boiling will continue |
| C. | Boiling will stop |
| D. | Vapour starts condensing |
| Answer» B. Temperature will rise and boiling will continue | |
| 57. |
Consider the following statements :Air washer can work as1. Humidifier only2. Dehumidifier only3. Filter onlyWhich of the statements given above is/are correct ? |
| A. | Only 1 |
| B. | Only 2 and 3 |
| C. | Only 1 and 3 |
| D. | 1, 2 and 3 |
| Answer» E. | |
| 58. |
Absolute humidity is defined as |
| A. | Weight of water vapour present in unit volume of air |
| B. | Weight of water vapour present in 1 kg of air |
| C. | Weight of moist air per m3 of volume |
| D. | none of the above |
| Answer» B. Weight of water vapour present in 1 kg of air | |
| 59. |
During an adiabatic saturation process of an unsaturated air, the parameters which remains constant is |
| A. | Dry bulb temperature |
| B. | Dew point temperature |
| C. | Thermodynamic wet bulb temperature |
| D. | Relative humidity |
| Answer» D. Relative humidity | |
| 60. |
Atmospheric air at a flow rate of 3 kg/s (on dry basis) enters a cooling and dehumidifying coil with an enthalpy of 85 kJ/kg of dry air and a humidity ratio of 19 grams/kg of dry air. The air leaves the coil with an enthalpy of 43 kJ/kg of dry air and a humidity ratio of 8 grams/kg of dry air. If the condensate water leaves the coil with an enthalpy of 67 kJ/kg, the required cooling capacity of the coil in kW is |
| A. | 75.0 |
| B. | 123.8 |
| C. | 128.2 |
| D. | 159.0 |
| Answer» C. 128.2 | |
| 61. |
In a Psychrometric chart, horizontal lines represent constant |
| A. | Humidity ratio and vertical lines represent constant dry bulb temperature |
| B. | Humidity ratio and vertical lines represent constant wet bulb temperature |
| C. | Dry bulb temperature and vertical lines represent constant absolute humidity ratio |
| D. | Wet bulb temperature and vertical lines represent constant humidity ratio |
| Answer» B. Humidity ratio and vertical lines represent constant wet bulb temperature | |
| 62. |
If a mass of moist air contained in a closed metallic vessel is heated, then its |
| A. | Relative humidity decrease |
| B. | Relative humidity increase |
| C. | Specific humidity increases |
| D. | Specific humidity decreases |
| Answer» B. Relative humidity increase | |
| 63. |
Humidostat is a device which is sensitive to |
| A. | Moisture changes |
| B. | Temperature changes |
| C. | Moisture and temperature changes |
| D. | None of the above |
| Answer» B. Temperature changes | |
| 64. |
A room contains 35 kg of dry air and 0.5 kg of water vapour. The total pressure and temperature of the air in the room are 100 kPa and 25°C respectively. Given that the saturation pressure for water at 25°C is 3.17 kPa, the relative humidity of the air in the room is |
| A. | 67% |
| B. | 55% |
| C. | 83% |
| D. | 71% |
| Answer» E. | |
| 65. |
Efficiency of the Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of coefficient of performance of reversed Carnot cycle refrigerator? |
| A. | 1.25 |
| B. | 0.8 |
| C. | 0.5 |
| D. | 0.25 |
| Answer» E. | |
| 66. |
If the relative humidity of atmospheric air is 100%, then the wet-bulb temperature will be |
| A. | more than dry-bulb temperature |
| B. | equal to dew-point temperature |
| C. | more than dew-point temperature |
| D. | less than dry-bulb temperature |
| Answer» C. more than dew-point temperature | |
| 67. |
In humidification process ________. |
| A. | relative humidity increases |
| B. | relative humidity decreases |
| C. | specific humidity increases |
| D. | specific humidity decreases |
| Answer» D. specific humidity decreases | |
| 68. |
A conference hall of the size 7m × 4m × 4m is filled with an air–water vapour mixture of 38° C, atmospheric pressure of 1 bar and RH 70%. The mass of air will be (assume Ps at 38° C = 0.06624 bar): |
| A. | 149.2 kg |
| B. | 119.2 kg |
| C. | 83.2 kg |
| D. | 169.7 kg |
| Answer» C. 83.2 kg | |
| 69. |
The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is |
| A. | Same |
| B. | More |
| C. | Less |
| D. | More or less depending on ambient conditions |
| Answer» D. More or less depending on ambient conditions | |
| 70. |
The refrigerant used in small tonnage commercial machines (hermetically sealed units) is |
| A. | Ammonia |
| B. | Carbon dioxide |
| C. | Sulphur dioxide |
| D. | R-12 |
| Answer» D. R-12 | |
| 71. |
In vapour compression cycle the condition off refrigerant is dry saturated vapour |
| A. | After passing through the condenser |
| B. | Before passing through the condenser |
| C. | After passing through the expansion or throttle valve |
| D. | Before entering the compressor |
| Answer» E. | |
| 72. |
In a vapour compression system, the condition of refrigerant is dry saturated vapour |
| A. | Before entering the compressor |
| B. | After leaving the compressor |
| C. | Before entering the condenser |
| D. | After leaving the condenser |
| Answer» B. After leaving the compressor | |
| 73. |
In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid |
| A. | After passing through the condenser |
| B. | Before passing through the condenser |
| C. | After passing through the expansion or throttle valve |
| D. | Before entering the expansion valve |
| Answer» E. | |
| 74. |
In vapour compression cycle, the condition of refrigerant is saturated liquid |
| A. | After passing through the condenser |
| B. | Before passing through the condenser |
| C. | After passing through the expansion throttle valve |
| D. | Before entering the expansion valve |
| Answer» B. Before passing through the condenser | |
| 75. |
If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be |
| A. | Same |
| B. | More |
| C. | Less |
| D. | More/less depending on rating |
| Answer» C. Less | |
| 76. |
Chaperon equation is a relation between |
| A. | Temperature, pressure and enthalpy |
| B. | Specific volume and enthalpy |
| C. | Temperature and enthalpy |
| D. | Temperature, pressure, specific volume and enthalpy |
| Answer» E. | |
| 77. |
The evaporator used in household refrigerators is |
| A. | Frosting evaporator |
| B. | Non-frosting evaporator |
| C. | Defrosting evaporator |
| D. | None of these |
| Answer» B. Non-frosting evaporator | |
| 78. |
An important characteristic of absorption system of refrigeration is |
| A. | noisy operation |
| B. | quiet operation |
| C. | cooling below 0°C |
| D. | very little power consumption |
| Answer» C. cooling below 0°C | |
| 79. |
The power per tonne of refrigeration is |
| A. | 3.5/C.O.P. |
| B. | C.O.P/3.5 |
| C. | 3.5 × C.O.P. |
| D. | None of these |
| Answer» B. C.O.P/3.5 | |
| 80. |
One ton of the refrigeration is |
| A. | The standard unit used in refrigeration problems |
| 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 hours |
| D. | The refrigeration effect to produce 1 ton of ice at NTP conditions |
| Answer» D. The refrigeration effect to produce 1 ton of ice at NTP conditions | |
| 81. |
The Freon group of refrigerants are |
| A. | Halocarbon refrigerants |
| B. | Zoetrope refrigerants |
| C. | Inorganic refrigerants |
| D. | Hydrocarbon refrigerants |
| Answer» B. Zoetrope refrigerants | |
| 82. |
Freon group of refrigerants are |
| A. | Inflammable |
| B. | Toxic |
| C. | Non-inflammable and toxic |
| D. | Nontoxic and non-inflammable |
| Answer» E. | |
| 83. |
During a refrigeration cycle, heat is rejected by the refrigerant in a |
| A. | Compressor |
| B. | Condenser |
| C. | Evaporator |
| D. | Expansion valve |
| Answer» C. Evaporator | |
| 84. |
The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by |
| A. | (C.O.P.)P = (C.O.P.)R + 2 |
| B. | (C.O.P.)P = (C.O.P.)R + 1 |
| C. | (C.O.P)P = (C.O.P)R - 1 |
| D. | (C.O.P)P = (C.O.P)R |
| Answer» C. (C.O.P)P = (C.O.P)R - 1 | |
| 85. |
The freezing point of R-12 is |
| A. | -86.6°C |
| B. | -95.2°C |
| C. | -107.7°C |
| D. | -135.8°C |
| Answer» E. | |
| 86. |
The general rule for rating refrigeration systems (excepting for CO₂ system) is to approximate following h.p. per ton of refrigeration |
| A. | 0.1 to 0.5 h.p. per ton of refrigeration |
| B. | 0.5 to 0.8 h.p. per ton of refrigeration |
| C. | 1 to 2 h.p. per ton of refrigeration |
| D. | 2 to 5 h.p. per ton of refrigeration |
| Answer» D. 2 to 5 h.p. per ton of refrigeration | |
| 87. |
The bypass factor (B. P. F.) in case of sensible heating of air is (Where td₁ = Dry bulb temperature of air entering the heating coil, td₂ = Dry bulb temperature of air leaving the heating coil, and td₃ = Dry bulb temperature of heating coil) |
| A. | (td₂ - td₃)/(td₃ - td₁) |
| B. | (td₃ - td₂)/(td₃ - td₁) |
| C. | (td₃ - td₁)/(td₂ - td₃) |
| D. | (td₃ - td₁)/(td₃ - td₂) |
| Answer» C. (td₃ - td₁)/(td₂ - td₃) | |
| 88. |
A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of -23°C. The Carnot coefficient of performance of cycle will be |
| A. | 0.2 |
| B. | 1.2 |
| C. | 5 |
| D. | 6 |
| Answer» D. 6 | |
| 89. |
The reciprocating refrigerant compressors are very suitable for |
| A. | Small displacements and low condensing pressures |
| B. | Large displacements and high condensing pressures |
| C. | Small displacements and high condensing pressures |
| D. | Large displacements and low condensing pressures |
| Answer» D. Large displacements and low condensing pressures | |
| 90. |
The humidity ratio or specific humidity is the mass of water vapour present in |
| A. | 1 m3 of wet air |
| B. | 1 m3 of dry air |
| C. | 1 kg of wet air |
| D. | 1 kg of dry air |
| Answer» E. | |
| 91. |
Most air cooled condensers are designed to operate with a temperature difference of |
| A. | 5°C |
| B. | 8°C |
| C. | 14°C |
| D. | 22°C |
| Answer» D. 22°C | |
| 92. |
In vapour compression cycle the condition of refrigerant is superheated vapour |
| A. | After passing through the condenser |
| B. | Before passing through the condenser |
| C. | After passing through the expansion or throttle valve |
| D. | Before entering the expansion valve |
| Answer» C. After passing through the expansion or throttle valve | |
| 93. |
The freezing point of sulphur dioxide is |
| A. | -56.6°C |
| B. | -75.2°C |
| C. | -77.7°C |
| D. | -135.8°C |
| Answer» C. -77.7°C | |
| 94. |
The coefficient of performance of Heat Pump is always _________ one. |
| A. | Equal to |
| B. | Less than |
| C. | Greater than |
| D. | None of these |
| Answer» D. None of these | |
| 95. |
The domestic refrigerator uses following type of compressor |
| A. | Centrifugal |
| B. | Axial |
| C. | Miniature sealed unit |
| D. | Piston type reciprocating |
| Answer» E. | |
| 96. |
A human body feels comfortable when the heat produced by the metabolism of human body is equal to the |
| A. | Heat dissipated to the surroundings |
| B. | Heat stored in the human body |
| C. | Sum of (A) and (B) |
| D. | Difference of (A) and (B) |
| Answer» D. Difference of (A) and (B) | |
| 97. |
In a vapour compression cycle, the refrigerant immediately after expansion valve is |
| A. | Liquid |
| B. | Sub-cooled liquid |
| C. | Saturated liquid |
| D. | Wet vapour |
| Answer» E. | |
| 98. |
In mechanical refrigeration system, the refrigerant has the maximum temperature |
| A. | In evaporator |
| B. | Before expansion valve |
| C. | Between compressor and condenser |
| D. | Between condenser and evaporator |
| Answer» D. Between condenser and evaporator | |
| 99. |
The air cooling system mostly used in transport type aircrafts is |
| A. | Simple air cooling system |
| B. | Simple evaporative air cooling system |
| C. | Bootstrap air cooling system |
| D. | All of these |
| Answer» D. All of these | |
| 100. |
The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and |
| A. | Carbon dioxide |
| B. | Sulphur dioxide |
| C. | Lithium bromide |
| D. | R-12 |
| Answer» D. R-12 | |