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Refrigeration and Air Conditioning MCQs

Free 94+ Refrigeration and Air Conditioning MCQs for PPSC, FPSC, NTS, and Pakistan government job tests. Practise below with answers and explanations.

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94 questions in this list. Select an option to practice, or open a question for the full page with explanation.

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Refrigeration and Air Conditioning

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1.Identify the statement that is incorrect regarding the lithium bromide absorption system.

Lithium bromide employed in the vapor absorption system is non-volatile.The lithium bromide system cannot function at temperatures below 0°C.In a lithium bromide system, a separator is utilized to condense and eliminate unwanted water vapor.The solution exiting the lithium bromide generator has a higher concentration than the solution entering it.Within the liquid heat exchanger, the weak solution transfers heat to the strong solution.

2.Identify the incorrect statement from the following:

The temperature of the substance being cooled must be lower than that of the evaporator.The refrigerant exits the condenser in a liquid state.Solar-driven absorption systems operate only intermittently.Frost accumulation on the evaporator decreases heat transfer efficiency.In refrigeration systems, refrigerant circulates to facilitate heat transfer.

3.Which of the following statements is accurate?

A refrigerant must possess a low latent heat value.For systems operating at low temperatures, a refrigerant with a low boiling point is preferred.Precooling and subcooling of a refrigerant refer to the same process.Superheating and sensible heat of a refrigerant are identical concepts.In direct-expansion chillers, refrigerant is contained within the lubricants.

4.In a vapor compression refrigeration cycle, what is the state of the refrigerant right after it passes through the expansion valve?

Completely liquidLiquid below saturation temperatureSaturated liquidMixture of liquid and vapor (wet vapor)Fully vaporized (dry vapor)

5.Which refrigerant is commonly utilized in absorption refrigeration systems?

R-11 (Freon-11)R-22 (Freon-22)Carbon dioxide (CO2)Sulfur dioxide (SO2)Ammonia

6.In a refrigeration cycle, the maximum temperature reached should ideally be:

Close to the refrigerant's critical temperatureExceeding the critical temperatureExactly at the critical temperatureSignificantly lower than the critical temperatureAny temperature is acceptable

7.What is one of the main reasons for sub-cooling the liquid refrigerant in a refrigeration system?

To prevent the compressor from overheatingTo lower the temperature at the compressor dischargeTo enhance the refrigeration capacityTo guarantee that only liquid refrigerant, without any vapor, reaches the expansion (throttling) valveNone of these

8.In a refrigeration cycle, how does the amount of heat absorbed compare to the heat expelled?

Greater than the heat rejectedSmaller than the heat rejectedEqual to the heat rejectedGreater for low capacity units and smaller for high capacity unitsSmaller for low capacity units and greater for high capacity units

9.What is the effect of frost buildup on the evaporator in a refrigerator?

Causes heat loss because heat transfer becomes inefficientEnhances the rate of heat transferHas no significant impactCan be prevented through appropriate design measuresLowers the power consumption of the compressor

10.How does the latent heat of vaporization of a refrigerant change when temperature and pressure decrease?

It reducesIt risesIt stays constantIt varies based on other conditionsNone of these

11.Which characteristic is considered undesirable in a refrigerant?

Excellent miscibility with lubricating oilHaving a low boiling temperatureBeing an efficient electrical conductorPossessing a high latent heat of vaporizationBeing non-flammable

12.Which statement correctly describes the direction of heat transfer between mediums in an ammonia absorption system?

From the concentrated solution to the diluted solutionFrom the diluted solution to the concentrated solutionFrom the concentrated solution to the ammonia vaporFrom the ammonia vapor to the diluted solutionFrom the ammonia vapor to the concentrated solution

13.What happens to the compressor's horsepower requirement if the evaporator temperature decreases while the condenser temperature remains unchanged?

Remains unchangedIncreasesDecreasesVaries based on system capacityCannot be determined

14.What is the maximum pressure that should be experienced within a refrigeration system?

Equal to the refrigerant's critical pressureSignificantly lower than the critical pressureConsiderably higher than the critical pressureClose to the critical pressureNo specific pressure limitation applies

15.A refrigeration system operates with a typical suction pressure of 10 kg/cm² gauge and a condensing pressure near 67 kg/cm². Which refrigerant is most likely used in this system?

AmmoniaCarbon dioxideFreonBrine solutionHydrocarbon-based refrigerant

16.In a vapor compression refrigeration cycle, at which component is the temperature at its minimum?

At the condenser unitInside the evaporator sectionWithin the compressorAt the expansion deviceIn the receiver tank

17.What is the approximate mass flow rate ratio of ammonia (NH3) to Freon-12 when delivering the same refrigeration capacity under identical temperature conditions?

Equal mass flow rates (1:1)Ammonia flow is one-ninth that of Freon-12 (1:9)Ammonia flow is nine times that of Freon-12 (9:1)Ammonia flow is one-third that of Freon-12 (1:3)Ammonia flow is three times that of Freon-12 (3:1)

18.How would you best describe the properties of ammonia?

harmless to healthdoes not catch fire easilypoisonous but not flammableextremely toxic and easily flammablenone of these descriptions apply

19.On a pressure-enthalpy diagram, what do the short horizontal lines represent?

Lines of constant pressureLines of constant temperatureLines of constant total heatLines of constant entropyLines of constant volume

20.What does one ton of refrigeration represent?

A commonly used unit for solving refrigeration calculationsThe amount of cooling generated by melting one ton of iceThe refrigeration capacity required to freeze one ton of water at 0°C into ice at 0°C within 24 hoursThe cooling effect needed to create one ton of ice under normal temperature and pressureThe refrigeration effect necessary to produce one ton of ice in one hour

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