MCQOPTIONS
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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.
| 251. |
The sub-cooling 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» C. Decreases C.O.P. | |
| 252. |
Reducing suction pressure in refrigeration cycle |
| A. | Lowers evaporation temperature |
| B. | Increases power required per ton of refrigeration |
| C. | Lowers compressor capacity because vapour is lighter |
| D. | All of the above |
| Answer» E. | |
| 253. |
A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is |
| A. | Ammonia |
| B. | Carbon dioxide |
| C. | Freon |
| D. | Brine |
| Answer» C. Freon | |
| 254. |
For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is ________ that for counter flow. |
| A. | Equal to |
| B. | Less than |
| C. | Greater than |
| D. | None of these |
| Answer» B. Less than | |
| 255. |
The specific humidity during heating and humidification process. |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 256. |
In chemical dehumidification process, |
| A. | Dew point temperature decreases |
| B. | Wet bulb temperature decreases |
| C. | Dry bulb temperature increases |
| D. | All of these |
| Answer» E. | |
| 257. |
The sensible heat factor during cooling and dehumidification process is given by (where h₁ = Enthalpy of air entering the cooling coil, h₂ = Enthalpy of air leaving the cooling coil, and hA = Enthalpy of air at the end of dehumidification process) |
| A. | (hA - h2)/ (h1 - h2) |
| B. | (h2 - hA)/ (h1 - h2) |
| C. | (h1 - h2)/ (hA - h2) |
| D. | (hA - h1)/ (h2 - h1) |
| Answer» B. (h2 - hA)/ (h1 - h2) | |
| 258. |
The sensible heat factor during the heating and humidification process is given by (where h₁ = Enthalpy of air entering the heating coil, h₂ = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process) |
| A. | (hA - h2)/ (h1 - h2) |
| B. | (h2 - hA)/ (h1 - h2) |
| C. | (h1 - h2)/ (hA - h2) |
| D. | (hA - h1)/ (h2 - h1) |
| Answer» E. | |
| 259. |
The capillary tube, as an expansion device, is used in |
| A. | Domestic refrigerators |
| B. | Water coolers |
| C. | Room air conditioners |
| D. | All of these |
| Answer» E. | |
| 260. |
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. | |
| 261. |
The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called |
| A. | Humidity ratio |
| B. | Relative humidity |
| C. | Absolute humidity |
| D. | Degree of saturation |
| Answer» C. Absolute humidity | |
| 262. |
For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then |
| A. | Bigger cabinet should be used |
| B. | Smaller cabinet should be used |
| C. | Perfectly tight vapour seal should be used |
| D. | Refrigerant with lower evaporation temperature should be used |
| Answer» D. Refrigerant with lower evaporation temperature should be used | |
| 263. |
Pick up the wrong statement. A refrigerant should have |
| A. | Tow specific heat of liquid |
| B. | High boiling point |
| C. | High latent heat of vaporisation |
| D. | Higher critical temperature |
| Answer» C. High latent heat of vaporisation | |
| 264. |
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. | |
| 265. |
The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity) |
| A. | 25°C DBT and 100% RH |
| B. | 20°C DBT and 80% RH |
| C. | 22°C DBT and 60% RH |
| D. | 25°C DBT and 40% RH |
| Answer» D. 25°C DBT and 40% RH | |
| 266. |
Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since |
| A. | These react with water vapour and cause acid rain |
| B. | These react with plants and cause greenhouse effect |
| C. | These react with oxygen and cause its depletion |
| D. | These react with ozone layer |
| Answer» E. | |
| 267. |
In which of the following refrigeration system, waste heat can be effectively used? |
| A. | Vapour compression cycle |
| B. | Vapour absorption cycle |
| C. | Air refrigeration cycle |
| D. | None of these |
| Answer» C. Air refrigeration cycle | |
| 268. |
A good refrigerant should have |
| A. | High latent heat of vaporisation and low freezing point |
| B. | High operating pressures and low freezing point |
| C. | High specific volume and high latent heat of vaporisation |
| D. | Low C.O.P. and low freezing point |
| Answer» B. High operating pressures and low freezing point | |
| 269. |
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 | |
| 270. |
For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of |
| A. | Copper |
| B. | Aluminium |
| C. | Steel |
| D. | Brass |
| Answer» D. Brass | |
| 271. |
Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation) |
| A. | 0.622 Pv / (Pb - Pv) |
| B. | μ/[1 - (1 - μ) (Ps/Pb)] |
| C. | [Pv (Pb - Pd)]/ [Pd (Pb - Pv)] |
| D. | None of these |
| Answer» C. [Pv (Pb - Pd)]/ [Pd (Pb - Pv)] | |
| 272. |
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 | |
| 273. |
The human body feels comfortable when the heat stored in the body is |
| A. | Positive |
| B. | Negative |
| C. | Zero |
| D. | None of these |
| Answer» D. None of these | |
| 274. |
In a refrigeration system, the expansion device is connected between the |
| A. | Compressor and condenser |
| B. | Condenser and receiver |
| C. | Receiver and evaporator |
| D. | Evaporator and compressor |
| Answer» D. Evaporator and compressor | |
| 275. |
The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P. |
| A. | More |
| B. | Less |
| C. | Equally |
| D. | Unpredictable |
| Answer» B. Less | |
| 276. |
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. | |
| 277. |
In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be |
| A. | 0.3 |
| B. | 0.6 |
| C. | 0.67 |
| D. | 1.5 |
| Answer» C. 0.67 | |
| 278. |
The thermostatic expansion valve is used in ________ type of evaporators. |
| A. | Flooded |
| B. | DX coil |
| C. | Dry |
| D. | None of these |
| Answer» D. None of these | |
| 279. |
During heating and humidification, the final relative humidity of air |
| A. | Can be lower or higher than that of the entering air |
| B. | Is lower than that of the entering air |
| C. | Is higher than that of the entering air |
| D. | None of the above |
| Answer» B. Is lower than that of the entering air | |
| 280. |
The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The bypass factor of the heating coil is |
| A. | 0.376 |
| B. | 0.4 |
| C. | 0.6 |
| D. | 0.67 |
| Answer» D. 0.67 | |
| 281. |
The vapour compression refrigerator employs the following cycle |
| A. | Rankine |
| B. | Carnot |
| C. | Reversed Rankine |
| D. | Reversed Carnot |
| Answer» E. | |
| 282. |
For air conditioning the operation theater in a hospital, the percentage of outside air in the air supplied is |
| A. | Zero |
| B. | 20 |
| C. | 50 |
| D. | 100 |
| Answer» E. | |
| 283. |
The central air conditioning system has ___________ overall efficiency as compared to individual systems. |
| A. | Same |
| B. | Lower |
| C. | Higher |
| D. | None of these |
| Answer» D. None of these | |
| 284. |
The lowest thermal diffusivity is of |
| A. | Iron |
| B. | Lead |
| C. | Aluminium |
| D. | Rubber |
| Answer» E. | |
| 285. |
In a pressure enthalpy chart, the space to the left of the saturated liquid line represents |
| A. | Wet vapour region |
| B. | Superheated vapour region |
| C. | Sub-cooled liquid region |
| D. | None of these |
| Answer» D. None of these | |
| 286. |
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 | |
| 287. |
The C.O.P. of a heat pump working on a reversed Carnot cycle is |
| A. | T₁/(T₂ - T₁) |
| B. | (T₂ - T₁)/T₁ |
| C. | (T₁ - T₂)/T₁ |
| D. | T₂/(T₂ - T₁) |
| Answer» E. | |
| 288. |
For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be |
| A. | Small |
| B. | High |
| C. | Equal |
| D. | Anything |
| Answer» B. High | |
| 289. |
During heating and dehumidification process, dry bulb temperature |
| A. | Remains constant |
| B. | Increases |
| C. | Decreases |
| D. | None of these |
| Answer» C. Decreases | |
| 290. |
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 | |
| 291. |
In aqua ammonia and Lithium bromide water absorption refrigeration systems, the refrigerants are respectively |
| A. | Water and water |
| B. | Water and lithium bromide |
| C. | Ammonia and lithium bromide |
| D. | Ammonia and water |
| Answer» E. | |
| 292. |
The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner. |
| A. | Same |
| B. | Less |
| C. | More |
| D. | None of these |
| Answer» C. More | |
| 293. |
Cooling water is required for following equipment in ammonia absorption plant |
| A. | Condenser |
| B. | Evaporator |
| C. | Absorber |
| D. | Condenser, absorber and separator (rectifier) |
| Answer» E. | |
| 294. |
The vertical and uniformly spaced lines on a psychrometric chart indicates |
| A. | Dry bulb temperature |
| B. | Wet bulb temperature |
| C. | Dew point temperature |
| D. | Specific humidity |
| Answer» B. Wet bulb temperature | |
| 295. |
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 | |
| 296. |
The curved lines on a psychrometric chart indicates |
| A. | Dry bulb temperature |
| B. | Wet bulb temperature |
| C. | Dew point temperature |
| D. | Relative humidity |
| Answer» E. | |
| 297. |
In a reversed Brayton cycle, the heat is absorbed by the air during |
| A. | Isentropic compression process |
| B. | Constant pressure cooling process |
| C. | Isentropic expansion process |
| D. | Constant pressure expansion process |
| Answer» E. | |
| 298. |
The wet bulb temperature at 100% relative humidity is ________ dry bulb temperature. |
| A. | Same as |
| B. | Lower than |
| C. | Higher than |
| D. | None of these |
| Answer» B. Lower than | |
| 299. |
The humidification process, on the psychrometric chart is shown by |
| A. | Horizontal line |
| B. | Vertical line |
| C. | Inclined line |
| D. | Curved line |
| Answer» C. Inclined line | |
| 300. |
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. | |