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MCQOPTIONS
This section includes 4791 Mcqs, each offering curated multiple-choice questions to sharpen your Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1651. |
Prandtl number (PN) is given by PN = .cp/k. |
| A. | Yes |
| B. | No |
| Answer» B. No | |
| 1652. |
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 | |
| 1653. |
Most thermostatic expansion valves are set for a superheat of |
| A. | 5 C |
| B. | 10 C |
| C. | 15 C |
| D. | 20 C |
| Answer» B. 10 C | |
| 1654. |
When the discharge pressure is too high in a refrigeration system, high pressure control is installed to stop the compressor. |
| A. | Correct |
| B. | Incorrect |
| Answer» B. Incorrect | |
| 1655. |
A grey body is one whose absorptivity does not vary with temperature and wave length of the incident ray. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 1656. |
During dehumidification process, the relative humidity |
| A. | remains constant |
| B. | increases |
| C. | decreases |
| Answer» D. | |
| 1657. |
The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness. |
| A. | Agree |
| B. | Disagree |
| Answer» B. Disagree | |
| 1658. |
For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is |
| A. | zero |
| B. | 20 |
| C. | 50 |
| D. | 100 |
| Answer» E. | |
| 1659. |
In case ofsensible cooling of air, the coil efficiency is given by |
| A. | B.P.F. - 1 |
| B. | 1 - B.P.F. |
| C. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-352-1.png"> |
| D. | 1 + B.P.F. |
| Answer» C. <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-352-1.png"> | |
| 1660. |
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 | |
| 1661. |
For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is |
| A. | reciprocating |
| B. | rotating |
| C. | centrifugal |
| D. | screw |
| Answer» D. screw | |
| 1662. |
R-11 has the highest critical point temperature. |
| A. | Correct |
| B. | Incorrect |
| Answer» B. Incorrect | |
| 1663. |
The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called |
| A. | coefficient of performance of refrigeration |
| B. | coefficient of performance of heat pump |
| C. | relative coefficient of performance |
| D. | refrigerating efficiency |
| Answer» B. coefficient of performance of heat pump | |
| 1664. |
Pressure of water vapour is given by |
| A. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/429-312-1.png"> |
| B. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/429-312-2.png"> |
| C. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/429-312-3.png"> |
| D. | none of these |
| Answer» E. | |
| 1665. |
The desirable property of a refrigerant is |
| A. | low boiling point |
| B. | high critical temperature |
| C. | high latent heat of vaporisation |
| D. | all of these |
| Answer» E. | |
| 1666. |
During dehumidification process, __________ remains constant. |
| A. | wet bulb temperature |
| B. | relative humidity |
| C. | dry bulb temperature |
| D. | specific humidity |
| Answer» D. specific humidity | |
| 1667. |
The expansion valve in a refrigerator controls the flow of refrigerant. |
| A. | Correct |
| B. | Incorrect |
| Answer» B. Incorrect | |
| 1668. |
A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with cp = 1 kJ/kg) |
| A. | 25 kJ/kg |
| B. | 50 kJ/kg |
| C. | l00 kJ/kg |
| D. | 125 kJ/kg |
| Answer» C. l00 kJ/kg | |
| 1669. |
The value of the wave length for maximum emissive power is given by |
| A. | Kirchhoff's law |
| B. | Stefan's law |
| C. | Wein's law |
| D. | Planck's law |
| Answer» D. Planck's law | |
| 1670. |
Emissivity of a body will be equal to its absorptivity at all temperatures. |
| A. | Yes |
| B. | No |
| Answer» C. | |
| 1671. |
The heat is transferred by conduction, convection and radiation in |
| A. | melting of ice |
| B. | boiler furnaces |
| C. | condensation of steam in condenser |
| D. | none of these |
| Answer» C. condensation of steam in condenser | |
| 1672. |
The temperature rise, between the condenser outlet and expansion valve in ammonia vapour compression system, should be as low as possible. |
| A. | Yes |
| B. | No |
| Answer» B. No | |
| 1673. |
Wet bulb temperature indicates the moisture content in air. |
| A. | Agree |
| B. | Disagree |
| Answer» B. Disagree | |
| 1674. |
The inclined and non-uniformly spaced straight lines on a psychrometric chart indicates wet bulb temperature. |
| A. | Agree |
| B. | Disagree |
| Answer» B. Disagree | |
| 1675. |
A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100 C and leaves at 60 C. A cold fluid enters the heat exchanger at 40 C. The mean temperature difference between the two fluids is |
| A. | 20 C |
| B. | 40 C |
| C. | 60 C |
| D. | 66.7 C |
| Answer» B. 40 C | |
| 1676. |
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 | |
| 1677. |
In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is |
| A. | heated and dehumidified |
| B. | heated and humidified |
| C. | cooled and humidified |
| D. | cooled and dehumidified |
| Answer» C. cooled and humidified | |
| 1678. |
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 by-pass factor of the heating coil is |
| A. | 0.376 |
| B. | 0.4 |
| C. | 0.6 |
| D. | 0.67 |
| Answer» D. 0.67 | |
| 1679. |
A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called |
| A. | automatic expansion valve |
| B. | high side float valve |
| C. | thermostatic expansion valve |
| D. | low side float valve |
| Answer» E. | |
| 1680. |
A vapour absorption refrigeration system |
| A. | gives noisy operation |
| B. | gives quiet operation |
| C. | requires little power consumption |
| D. | cools below 0 C |
| Answer» C. requires little power consumption | |
| 1681. |
The relative humidity lines on a psychrometric chart are |
| A. | vertical and uniformly spaced |
| B. | horizontal and uniformly spaced |
| C. | horizontal and non-uniformly spaced |
| D. | curved lines |
| Answer» E. | |
| 1682. |
The C.O.P. of a heat pump working on a reversed Carnot cycle is |
| A. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/415-144-1.png"> |
| B. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/415-144-2.png"> |
| C. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/415-144-3.png"> |
| D. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/415-144-4.png"> |
| Answer» E. | |
| 1683. |
For unsaturated air, the dew point temperature is __________ wet bulb temperature. |
| A. | equal to |
| B. | less than |
| C. | more than |
| Answer» C. more than | |
| 1684. |
The heat transfer by conduction through a thick cylinder(Q) is given by (where T1 = Higher temperature, T2 = Lower temperature, r1 = Inside radius, r2 = Outside radius, l = Length of cylinder, and k = Thermal conductivity) |
| A. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/405-32-1.png"> |
| B. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/405-32-2.png"> |
| C. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/405-32-3.png"> |
| D. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/405-32-4.png"> |
| Answer» B. <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/405-32-2.png"> | |
| 1685. |
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. | |
| 1686. |
The operating temperature of a cold storage is - 2 C. The heat leakage from the surrounding is 30 kW for the ambient temperature of 40 C. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is |
| A. | 1.86 kW |
| B. | 3.72 kW |
| C. | 7.44 kW |
| D. | 18.6 kW |
| Answer» E. | |
| 1687. |
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. | |
| 1688. |
The __________ point of ammonia is -77.7 C. |
| A. | freezing |
| B. | boiling |
| Answer» B. boiling | |
| 1689. |
Sulphur dioxide has the lowest boiling point. |
| A. | Yes |
| B. | No |
| Answer» C. | |
| 1690. |
In a psychrometric chart, dew point temperature lines are horizontal and non-uniformly spaced. |
| A. | Correct |
| B. | Incorrect |
| Answer» B. Incorrect | |
| 1691. |
The air cooling system mostly used in transport type aircrafts is |
| A. | simple air cooling system |
| B. | simple evaporative air cooling system |
| C. | boot-strap air cooling system |
| D. | all of these |
| Answer» D. all of these | |
| 1692. |
The by-pass factor, in case of sensible cooling of air, is given by (where td1 = Dry bulb temperature of air entering the cooling coil, td2 = Dry bulb temperature of air leaving the cooling coil, and td3 = Dry bulb temperature of the cooling coil) |
| A. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-351-1.png"> |
| B. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-351-2.png"> |
| C. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-351-3.png"> |
| D. | <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-351-4.png"> |
| Answer» C. <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/432-351-3.png"> | |
| 1693. |
During sensible heating of air __________ decreases. |
| A. | wet bulb temperature |
| B. | relative humidity |
| C. | dry bulb temperature |
| D. | specific humidity |
| Answer» C. dry bulb temperature | |
| 1694. |
The overall coefficient of heat transfer is used in problems of |
| A. | conduction |
| B. | convection |
| C. | radiation |
| D. | conduction and convection |
| Answer» E. | |
| 1695. |
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. | |
| 1696. |
In aircraft, air refrigeration Cycle is used because of |
| A. | low weight per tonne of refrigeration |
| B. | high heat transfer rate |
| C. | low temperature at high altitudes |
| D. | higher coefficient of performance |
| Answer» B. high heat transfer rate | |
| 1697. |
If the evaporator temperature is kept constant, the coefficient of performance of a refrigeration cycle __________ with the increase in condenser temperature. |
| A. | increases |
| B. | decreases |
| Answer» C. | |
| 1698. |
A one tonne refrigerating machine means that |
| A. | one tonne is the total mass of machine |
| B. | one tonne refrigerant is used |
| C. | one tonne of water can be converted into ice |
| D. | one tonne of ice when melts from and at 0 C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min |
| Answer» E. | |
| 1699. |
The evaporator used in house-hold refrigerators is |
| A. | frosting evaporator |
| B. | non-frosting evaporator |
| C. | defrosting evaporator |
| D. | none of these |
| Answer» B. non-frosting evaporator | |
| 1700. |
The lowest thermal diffusivity is of |
| A. | iron |
| B. | lead |
| C. | aluminium |
| D. | rubber |
| Answer» E. | |