MCQOPTIONS
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MCQOPTIONS
This section includes 368 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
_ In order to collect liquid refrigerant and to prevent it from going to a ________, a device known as accumulator is used at the suction of compressor.$? |
| A. | Compressor |
| B. | Condenser |
| C. | Expansion valve |
| D. | Evaporator |
| Answer» B. Condenser | |
| 152. |
_ A bootstrap air cooling system has$? |
| A. | One heat exchanger |
| B. | Two heat exchangers |
| C. | Three heat exchangers |
| D. | Four heat exchangers |
| Answer» C. Three heat exchangers | |
| 153. |
_ The wet bulb temperature at 100% relative humidity is ________ dew point temperature.$? |
| A. | Same as |
| B. | Lower than |
| C. | Higher than |
| D. | None of these |
| Answer» B. Lower than | |
| 154. |
_ Where does the lowest temperature occur in a vapour compression cycle?$? |
| A. | Condenser |
| B. | Evaporator |
| C. | Compressor |
| D. | Expansion valve |
| Answer» C. Compressor | |
| 155. |
_ Refrigeration in aeroplanes usually employs the following refrigerant$? |
| A. | CO2 |
| B. | Freon-11 |
| C. | Freon-22 |
| D. | Air |
| Answer» E. | |
| 156. |
_ On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process$? |
| A. | Involves no change in volume |
| B. | Takes place at constant temperature |
| C. | Takes place at constant entropy |
| D. | Takes place at constant pressure |
| Answer» E. | |
| 157. |
_ The horizontal and non-uniformly spaced lines on a psychrometric chart indicates$? |
| A. | Dry bulb temperature |
| B. | Wet bulb temperature |
| C. | Dew point temperature |
| D. | Specific humidity |
| Answer» D. Specific humidity | |
| 158. |
_ For unsaturated air, the dew point temperature is __________ wet bulb temperature.$? |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» C. More than | |
| 159. |
_ The C.O.P. of an absorption type refrigerator is given by (where T‚ÇÅ = Temperature at which the working substance receives heat, T‚ÇÇ = Temperature of cooling water, and T‚ÇÉ = Evaporator temperature)$? |
| A. | [T‚ÇÅ (T‚ÇÇ - T‚ÇÉ)] / [T‚ÇÉ (T‚ÇÅ - T‚ÇÇ)] |
| B. | [T‚ÇÉ (T‚ÇÅ - T‚ÇÇ)]/ [T‚ÇÅ (T‚ÇÇ - T‚ÇÉ)] |
| C. | [T‚ÇÅ (T‚ÇÅ - T‚ÇÇ)] / [T‚ÇÉ (T‚ÇÇ - T‚ÇÉ)] |
| D. | [T‚ÇÉ (T‚ÇÇ - T‚ÇÉ)] / [T‚ÇÅ (T‚ÇÅ - T‚ÇÇ)] |
| Answer» C. [T‚Äö√á√Ö (T‚Äö√á√Ö - T‚Äö√á√á)] / [T‚Äö√á√â (T‚Äö√á√á - T‚Äö√á√â)] | |
| 160. |
_ The emissivity of a polished silver body is _________ as compared to black body.$? |
| A. | Same |
| B. | Low |
| C. | Very low |
| D. | High |
| Answer» D. High | |
| 161. |
_ A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be$? |
| A. | Lack of cooling water |
| B. | Water temperature being high |
| C. | Dirty condenser surface |
| D. | All of these |
| Answer» E. | |
| 162. |
_ The vapour compression refrigerator employs the following cycle$? |
| A. | Rankine |
| B. | Carnot |
| C. | Reversed Rankine |
| D. | Reversed Carnot |
| Answer» E. | |
| 163. |
_ Critical pressure of a liquid is the pressure$? |
| A. | Above which liquid will remain liquid |
| B. | Above which liquid becomes gas |
| C. | Above which liquid becomes vapour |
| D. | Above which liquid becomes solid |
| Answer» B. Above which liquid becomes gas | |
| 164. |
_ If a gas is to be liquefied, its temperature must be$? |
| A. | Increased to a value above its critical temperature |
| B. | Reduced to a value below its critical temperature |
| C. | Equal to critical temperature |
| D. | None of the above |
| Answer» D. None of the above | |
| 165. |
_ The wet bulb temperature during sensible cooling of air$? |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» D. None of these | |
| 166. |
_ The superheated vapour region, in a pressure enthalpy chart, is represented by the space$? |
| A. | To the left of saturated liquid line |
| B. | To the right of saturated liquid line |
| C. | Between the saturated liquid line and saturated vapour line |
| D. | None of the above |
| Answer» D. None of the above | |
| 167. |
_ In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about$? |
| A. | 1 |
| B. | 1.25 |
| C. | 2.15 |
| D. | 5.12 |
| Answer» C. 2.15 | |
| 168. |
_ The superheating in a refrigeration cycle$? |
| A. | Does not alter C.O.P. |
| B. | Increases C.O.P. |
| C. | Decreases C.O.P. |
| D. | None of these |
| Answer» D. None of these | |
| 169. |
_ The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called$? |
| A. | Humidity ratio |
| B. | Relative humidity |
| C. | Absolute humidity |
| D. | Degree of saturation |
| Answer» E. | |
| 170. |
_ The specific humidity during heating and humidification process.$? |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 171. |
_ In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by$? |
| A. | Liquid pump |
| B. | Generator |
| C. | Absorber and generator |
| D. | Absorber, generator and liquid pump |
| Answer» E. | |
| 172. |
_ R-12 is generally preferred over R-22 in deep freezers since$? |
| A. | It has low operating pressures |
| B. | It gives higher coefficient of performance |
| C. | It is miscible with oil over large range of temperatures |
| D. | All of the above |
| Answer» D. All of the above | |
| 173. |
_ A refrigerant compressor is used to$? |
| A. | Raise the pressure of the refrigerant |
| B. | Raise the temperature of the refrigerant |
| C. | Circulate the refrigerant through the refrigerating system |
| D. | All of the above |
| Answer» E. | |
| 174. |
_ During dehumidification process, _________ remains constant.$? |
| A. | Wet bulb temperature |
| B. | Relative humidity |
| C. | Dry bulb temperature |
| D. | Specific humidity |
| Answer» D. Specific humidity | |
| 175. |
_ The difference between dry bulb temperature and wet bulb temperature, is called$? |
| A. | Dry bulb depression |
| B. | Wet bulb depression |
| C. | Dew point depression |
| D. | Degree of saturation |
| Answer» C. Dew point depression | |
| 176. |
_ The coefficient of performance of Electrolux refrigerator is the ratio of$? |
| A. | Heat supplied by the gas burner to the heat absorbed by the evaporator |
| B. | Heat absorbed by the evaporator to the heat supplied by the gas burner |
| C. | Heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner |
| D. | Heat absorbed by the evaporator minus the heat supplied by the gas burner to the heat absorbed by the evaporator |
| Answer» C. Heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner | |
| 177. |
_ Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of C.O.P. of reversed Carnot Cycle?$? |
| A. | 1.25 |
| B. | 0.8 |
| C. | 0.5 |
| D. | 0.25 |
| Answer» E. | |
| 178. |
_ Allowable pressure on high pressure side or ammonia absorption system is of the order of$? |
| A. | Atmospheric pressure |
| B. | Slightly above atmospheric pressure |
| C. | 24 bars |
| D. | 56 bars |
| Answer» E. | |
| 179. |
_ The alignment circle is marked on the psychrometric chart at$? |
| A. | 20°C DBT and 50% RH |
| B. | 26°C DBT and 50% RH |
| C. | 20°C DBT and 60% RH |
| D. | 26°C DBT and 60% RH |
| Answer» C. 20¬¨‚àûC DBT and 60% RH | |
| 180. |
_ A thermostatic expansion valve in a refrigeration system$? |
| A. | Ensures the evaporator completely filled with refrigerant of the load |
| B. | Is suitable only for constant load systems |
| C. | Maintains different temperatures in evaporator in proportion to load |
| D. | None of the above |
| Answer» B. Is suitable only for constant load systems | |
| 181. |
_ The process, generally used in winter air-conditioning to warm and humidity the air, is called$? |
| A. | Humidification |
| B. | Dehumidification |
| C. | Heating and humidification |
| D. | Cooling and dehumidification |
| Answer» D. Cooling and dehumidification | |
| 182. |
_ The pressure at the outlet of a refrigerant compressor is called$? |
| A. | Suction pressure |
| B. | Discharge pressure |
| C. | Critical pressure |
| D. | Back pressure |
| Answer» C. Critical pressure | |
| 183. |
_ The domestic refrigerator uses following type of compressor$? |
| A. | Centrifugal |
| B. | Axial |
| C. | Miniature sealed unit |
| D. | Piston type reciprocating |
| Answer» E. | |
| 184. |
_ A vapour absorption refrigerator uses _________ as a refrigerant.$? |
| A. | Water |
| B. | Ammonia |
| C. | Freon |
| D. | Aqua-ammonia |
| Answer» E. | |
| 185. |
_ In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is$? |
| A. | Less than 2 kg |
| B. | More than or equal to 3.65 kg |
| C. | More than 10 kg |
| D. | There is no such consideration |
| Answer» C. More than 10 kg | |
| 186. |
_ The unit of thermal diffusivity is$? |
| A. | m/hK |
| B. | m/h |
| C. | m²/h |
| D. | m²/hK |
| Answer» D. m¬¨‚â§/hK | |
| 187. |
_ The boiling point of ________ is 10.5°C.$? |
| A. | Ammonia |
| B. | R-12 |
| C. | Sulphur dioxide |
| D. | Carbon dioxide |
| Answer» D. Carbon dioxide | |
| 188. |
_ The heat rejection factor (HRF) is given by$? |
| A. | 1 + C.O.P |
| B. | 1 - C.O.P. |
| C. | 1 + (1/C.O.P) |
| D. | 1 - (1/C.O.P) |
| Answer» D. 1 - (1/C.O.P) | |
| 189. |
_ The refrigerant used in small tonnage commercial machines (hermetically sealed units) is$? |
| A. | Ammonia |
| B. | Carbon dioxide |
| C. | Sulphur dioxide |
| D. | R-12 |
| Answer» D. R-12 | |
| 190. |
_ If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be$? |
| A. | Same |
| B. | More |
| C. | Less |
| D. | More/less depending on rating |
| Answer» C. Less | |
| 191. |
_ One ton of the refrigeration is$? |
| A. | The standard unit used in refrigeration problems |
| B. | The cooling effect produced by melting 1 ton of ice |
| C. | The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours |
| D. | The refrigeration effect to produce 1 ton of ice at NTP conditions |
| Answer» D. The refrigeration effect to produce 1 ton of ice at NTP conditions | |
| 192. |
_ The freezing point of R-12 is$? |
| A. | -86.6°C |
| B. | -95.2°C |
| C. | -107.7°C |
| D. | -135.8°C |
| Answer» E. | |
| 193. |
_ In a vapour compression refrigeration system, a throttle valve is used in place of an expander because$? |
| A. | It considerably reduces mass of the system |
| B. | It improves the C.O.P., as the condenser is small |
| C. | The positive work in isentropic expansion of liquid is very small |
| D. | It leads to significant cost reduction |
| Answer» D. It leads to significant cost reduction | |
| 194. |
_ The minimum temperature to which water can be cooled in a cooling tower is$? |
| A. | Dew point temperature of air |
| B. | Wet bulb temperature of air |
| C. | Dry bulb temperature of air |
| D. | Ambient air temperature |
| Answer» C. Dry bulb temperature of air | |
| 195. |
_ In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature$? |
| A. | Which lies between the dry bulb and wet bulb temperatures of the incoming stream |
| B. | Which lies between the wet bulb and dew point temperatures of the incoming stream |
| C. | Which is lower than the dew point temperature of the incoming stream |
| D. | Of adiabatic saturation of incoming stream |
| Answer» D. Of adiabatic saturation of incoming stream | |
| 196. |
__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¬¨‚àûC | |
| 197. |
__Presence of moisture in a refrigerant affects the working of__ |
| A. | Compressor |
| B. | Condenser |
| C. | Evaporator |
| D. | Expansion valve |
| Answer» E. | |
| 198. |
__The COP of a domestic refrigerator__ |
| A. | Is less than 1 |
| B. | Is more than 1 |
| C. | Is equal to 1 |
| D. | Depends upon the make |
| Answer» C. Is equal to 1 | |
| 199. |
__Dry bulb temperature is the temperature of air recorded by a thermometer, when__ |
| A. | It is not affected by the moisture present in the air |
| B. | Its bulb is surrounded by a wet cloth exposed to the air |
| C. | The moisture present in it begins to condense |
| D. | None of the above |
| Answer» B. Its bulb is surrounded by a wet cloth exposed to the air | |
| 200. |
__The colour of the flame of halide torch, in case of leakage of Freon refrigerant, will change to__ |
| A. | Bright green |
| B. | Yellow |
| C. | Red |
| D. | Orange |
| Answer» B. Yellow | |