Refrigeration and Air Conditioning MCQ Pdf Download

1. Superheating in a refrigeration cycle

A. Increases C.O.P.

B. Decreases C.O.P.

C. C.O.P. remains unaltered

D. Other factors decide C.O.P.

Answer: Option B

Solution:

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2. Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.

A. Equalize

B. Reduce

C. Increase

D. None of these

Answer: Option C

Solution:

Hydrogen is used in Electrolux refrigeration system so as to increase the rate of evaporation of the liquid ammonia passing through the evaporator.

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3. The dehumidification process, on the psychrometric chart, is shown by

A. Horizontal line

B. Vertical line

C. Inclined line

D. Curved line

Answer: Option B

Solution:

The dehumidification process, on the psychrometric chart, is shown by Vertical line

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4. 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: Option C

Solution:

The process, generally used in winter air-conditioning to warm and humidity the air, is called Heating and humidification

5. The process, generally used in summer air conditioning to cool and

dehumidify the air, is called

A. Humidification

B. Dehumidification

C. Heating and humidification

D. Cooling and dehumidification

Answer: Option D

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6. The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called

A. Wet bulb temperature

B. Dry bulb temperature

C. Dew point temperature

D. None of these

Answer: Option B

Solution:

The temperature of air recorded by a thermometer, when it is not affected by the moisture present in the air, is called Dry bulb temperature

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7. The temperature of air recorded by a thermometer, when its bulb is

surrounded by a wet cloth exposed to the air, is called

A. Wet bulb temperature

B. Dry bulb temperature

C. Dew point temperature

D. None of these

Answer: Option A

Solution:

The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called Wet bulb temperature

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8. The thermostatic expansion valve operates on the changes in the

A. Degree of superheat at exit from the evaporator

B. Temperature of the evaporator

C. Pressure in the evaporator

D. None of the above

Answer: Option A

Solution:

The thermostatic expansion valve operates on the changes in the Degree of superheat at exit from the evaporator

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9. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be

A. 1/4

B. 1/3

C. 3

D. 4

Answer: Option D

Solution:

The coefficient of performance or C.O.P. (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work required.

10. A standard ice point temperature corresponds to the temperature of

A. Water at 0°C

B. Ice at 4°C

C. Solid and dry ice

D. Mixture of ice and water under equilibrium conditions

Answer: Option D

Solution:

A standard ice point temperature corresponds to the temperature of Mixture of ice and water under equilibrium conditions

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11. The leakage in a refrigeration system using ammonia is detected by

A. Halide torch

B. Sulphur sticks

C. Soap and water

D. All of these

Answer: Option B

Solution:

The leakage in a refrigeration system using ammonia is detected by Sulphur sticks

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12. The lower horizontal line of the refrigeration cycle plotted on pressureenthalpy diagram represents

A. Condensation of the refrigerant vapour

B. Evaporation of the refrigerant liquid

C. Compression of the refrigerant vapour

D. Metering of the refrigerant liquid

Answer: Option B

Solution:

The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents Evaporation of the refrigerant liquid

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13. Which of the following refrigerant is highly toxic and flammable?

A. Ammonia

B. Carbon dioxide

C. Sulphur dioxide

D. R-12

Answer: Option A

Solution:

Ammonia is highly toxic and flammable.

14. The wet bulb depression indicates _________ humidity of the air.

A. Absolute

B. Relative

C. Specific

D. None of these

Answer: Option B

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16. The specific humidity during dehumidification process

A. Remains constant

B. Increases

C. Decreases

D. None of these

Answer: Option C

Solution:

The specific humidity during dehumidification process Decreases

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17. The specific humidity during humidification process

A. Remains constant

B. Increases

C. Decreases

D. None of these

Answer: Option B

Solution:

The specific humidity during humidification process Increases

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18. The ratio of heat extracted in the refrigerator to the work-done 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: Option A

Solution:

The efficiency of a refrigerator or heat pump is given by a parameter called the coefficient of performance (C.O.P.).

The C.O.P. of a refrigerator is given by the following equation:

Answer & Solution

C.O.P. = Desired Output/ Required Input

= Cooling Effect/ Work Input

= QL/W

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19. The material of pipe lines for a system using Freon as a refrigerant should be

A. Brass

B. Copper

C. Steel

D. Aluminium

Answer: Option B

Solution:

The material of pipe lines for a system using Freon as a refrigerant should be copper

20. The vapour pressure of refrigerant should be

A. Lower than atmospheric pressure

B. Higher than atmospheric pressure

C. Equal to atmospheric pressure

D. Could be anything

Answer: Option B

Solution:

The vapour pressure of refrigerant should be Higher than atmospheric pressure

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21. Moisture should be removed from refrigerants to avoid

A. Freezing at the expansion valve

B. Restriction to refrigerant flow

C. Corrosion of steel plates

D. All of these

Answer: Option D

Solution:

Moisture should be removed from refrigerants to avoid

- Freezing at the expansion valve

- Restriction to refrigerant flow

- Corrosion of steel plates

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22. Air refrigerator works on

A. Reversed Carnot cycle

B. Bell Coleman cycle

C. Both (A) and (B)

D. None of these

Answer: Option C

Solution:

Air cycle refrigeration works on Reversed Carnot cycle and Bell Coleman cycle.

Air is compressed and then heat removed, this air is then expanded to a lower temperature than before it was

compressed.

Work is taken out of the air by an expansion turbine, which removes energy as the blades are driven round by the expanding air.

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23. The bypass factor of a cooling coil decreases with

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A. Decrease in fin spacing and increase in number of rows

B. Increase in fin spacing and increase in number of rows

C. Increase in fin spacing and decrease in number of rows

D. Decrease in fin spacing and decrease in number of rows

Answer: Option A

Solution:

The bypass factor is a function of the airflow, number of rows, surface temperature, number of fins per inch,

height of fins and many other construction attributes of coils.

The bypass factor of a cooling coil decreases with decrease in fin spacing and increase in number of rows.

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24. The formation of frost on cooling coils in a refrigerator

A. Increases heat transfer

B. Improves C.O.P. of the system

C. Increases power consumption

D. Reduces power consumption

Answer: Option C

Solution:

The formation of frost on cooling coils in a refrigerator increases power consumption

25. The boiling point of ammonia is

A. -10.5°C

B. -30°C

C. -33.3°C

D. -77.7°C

Answer: Option C

Solution:

The boiling point of ammonia is -33.3°C

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26. Moisture in Freon refrigeration system causes

A. Ineffective refrigeration

B. High power consumption

C. Freezing automatic regulating valve

D. Corrosion of whole system

Answer: Option C

Solution:

Moisture in Freon refrigeration system causes Freezing automatic regulating valve

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27. 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. 100 kJ/kg

D. 125 kJ/kg

Answer: Option B

Solution:

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 50 kJ/kg

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28. The relative humidity is defined as

A. The mass of water vapour present in 1 m of dry air

B. The mass of water vapour present in 1 kg of dry air

C. 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

D. 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

Answer: Option D

Solution:

The relative humidity is defined as 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.

29. The wet bulb temperature during sensible cooling of air

A. Remains constant

B. Increases

C. Decreases

D. None of these

Answer: Option C

Solution:

The wet bulb temperature during sensible cooling of air Decreases

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30. The dry bulb temperature during sensible heating of air

A. Remains constant

B. Increases

C. Decreases

D. None of these

Answer: Option B

Solution:

The dry bulb temperature during sensible heating of air Increases

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Refrigeration and Air Conditioning MCQ Pdf Download

What is refrigeration and air conditioning in mechanical engineering?

Refrigeration and air conditioning are two related fields within mechanical engineering that deal with the manipulation of air and temperature in indoor spaces.

Refrigeration involves the cooling of a space or a substance by removing heat from it, usually by using a refrigerant fluid that undergoes a phase change from a liquid to a gas and back again. The process of refrigeration is used in a variety of applications, including food preservation, air conditioning, and industrial cooling.

Air conditioning, on the other hand, is the process of controlling and maintaining the temperature, humidity, and air quality of an indoor space to ensure human comfort and health. Air conditioning systems typically involve the circulation of air through a building or structure, and the manipulation of temperature and humidity using various techniques, including refrigeration and dehumidification.

Both refrigeration and air conditioning are important fields within mechanical engineering, with applications in residential, commercial, and industrial settings. Mechanical engineers working in these fields may design, install, and maintain refrigeration and air conditioning systems, as well as develop new technologies and improve existing systems for greater efficiency and sustainability.

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What is refrigeration and air conditioning?

Refrigeration and air conditioning are two closely related technologies used to control temperature and humidity in indoor and outdoor spaces.

Refrigeration refers to the process of removing heat from a closed space, usually by circulating a refrigerant through a system of pipes, compressors, and condensers. This process is used to create a cooling effect, which is commonly used in refrigerators, freezers, and air conditioning systems to keep food and beverages cool or to provide a comfortable indoor environment.

Air conditioning, on the other hand, specifically refers to the process of controlling both temperature and humidity in an indoor environment, usually by using a refrigeration system to cool and dehumidify the air. Air conditioning is commonly used in homes, offices, and other buildings to provide a comfortable and healthy indoor environment.

Both refrigeration and air conditioning systems can be complex and involve a range of components, including compressors, evaporators, condensers, expansion valves, and refrigerants. They require skilled professionals to design, install, and maintain them to ensure their safe and efficient operation.

What is the difference between air conditioning and refrigeration PDF?

Air conditioning and refrigeration are both methods of cooling, but they have different purposes and applications.

Air conditioning is used to cool and dehumidify the air in a room or a building to create a comfortable environment for people to live or work in. The air conditioning system works by taking warm air from inside the building, passing it through an evaporator coil that contains a refrigerant, and then blowing the cooled and dehumidified air back into the building through ducts and vents.

Refrigeration, on the other hand, is used to cool and preserve food, beverages, and other perishable goods. The refrigeration system works by taking heat from the interior of a refrigerated space and releasing it to the exterior environment. This is done through a closed loop of pipes that circulate a refrigerant, which absorbs heat as it evaporates and releases it as it condenses.

The primary difference between air conditioning and refrigeration is the purpose for which they are used. Air conditioning is used for human comfort, while refrigeration is used for preserving perishable goods. Additionally, air conditioning is typically used on a larger scale to cool entire buildings, while refrigeration is typically used on a smaller scale to cool individual units or rooms, such as refrigerators or freezers.

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What are the 5 parts of refrigerator?

The five basic parts of a refrigerator are:

Compressor: The compressor is the heart of the refrigerator, responsible for compressing and circulating the refrigerant throughout the system. It pumps refrigerant through the condenser, evaporator, and back to the compressor to keep the system running.

Condenser: The condenser is a heat exchanger located on the outside of the refrigerator. It cools and condenses the high-pressure, high-temperature refrigerant vapor from the compressor, turning it into a high-pressure liquid.

Evaporator: The evaporator is a heat exchanger located inside the refrigerator. It absorbs heat from the food and air inside the refrigerator and transfers it to the refrigerant, which then carries the heat to the condenser.

Expansion valve: The expansion valve is a small device that controls the flow of refrigerant between the high-pressure side of the system (condenser) and the low-pressure side (evaporator). It reduces the pressure of the refrigerant and turns it into a low-pressure, low-temperature liquid before it enters the evaporator.

Refrigerant: The refrigerant is the substance that absorbs and releases heat as it circulates through the system. It undergoes a phase change from a low-pressure gas to a high-pressure liquid and back to a gas as it flows through the different parts of the system. Common refrigerants used in refrigerators include R134a and R600a.

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What are the basics of refrigeration?

Refrigeration is a process of removing heat from a space or substance and transferring it to another location. The basics of refrigeration include the following:

Compression: A refrigerant gas is compressed by a compressor, which raises its temperature and pressure.

Condensation: The compressed refrigerant gas is then cooled down by passing it through a condenser. This causes the gas to condense into a liquid, releasing heat in the process.

Expansion: The high-pressure liquid refrigerant is then passed through an expansion valve or orifice, which reduces its pressure and causes it to evaporate into a low-pressure gas.

Evaporation: The low-pressure refrigerant gas is then passed through an evaporator, which absorbs heat from the surrounding environment, such as a refrigerated space or substance, and causes the refrigerant to return to a low-temperature, low-pressure state.

Refrigerant cycle: The refrigerant is then cycled back to the compressor, where the process begins again.

By repeating this cycle, refrigeration systems are able to remove heat from one location and transfer it to another, which is useful in a variety of applications, such as air conditioning, refrigeration of food and beverages, and industrial processes that require cooling.

What are the 4 stages of refrigerant?

Refrigerant is a substance used in refrigeration systems to absorb and release heat to achieve cooling. The four stages of refrigerant are:

Compression: The refrigerant is compressed by a compressor, which increases its pressure and temperature.

Condensation: The hot, high-pressure refrigerant then flows through a condenser, where it releases heat and condenses into a liquid.

Expansion: The liquid refrigerant then passes through an expansion valve or device, which reduces its pressure and temperature.

Evaporation: The low-pressure, low-temperature refrigerant then flows through an evaporator, where it absorbs heat and evaporates into a gas, completing the refrigeration cycle.

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What are the five 5 methods of refrigeration?

There are several methods of refrigeration, but here are five common ones:

Vapor compression refrigeration: This is the most common method of refrigeration, and it works by compressing a refrigerant gas (such as R-134a or R-410a) to a high pressure and then allowing it to expand through a valve. This expansion causes the gas to cool down, which is used to remove heat from the refrigerated space.

Absorption refrigeration: This method uses a solution of water and a refrigerant (such as ammonia or lithium bromide) to remove heat from a space. The solution is heated, which causes the refrigerant to evaporate and absorb heat. The refrigerant is then condensed and the process repeats.

Thermoelectric refrigeration: This method uses the Peltier effect, which occurs when a current is passed through two different conductive materials. This causes one side to absorb heat and the other to release it, which can be used to create a temperature difference and cool a space.

Gas cycle refrigeration: This method uses a gas (such as helium or hydrogen) that is compressed and then expanded through a turbine. The expansion causes the gas to cool down, and this cooling effect is used to remove heat from a refrigerated space.

Magnetic refrigeration: This method uses a magnetic field to control the temperature of a material. When a magnetic field is applied to a magnetic material, it causes it to heat up, and when the field is removed, it cools down. This effect can be used to create a temperature difference and cool a space.

What is refrigeration Mcq?

Refrigeration MCQ stands for Multiple Choice Questions related to the topic of refrigeration. These questions are designed to test the knowledge and understanding of a person on the principles, working, components, and applications of refrigeration systems.

Refrigeration MCQs can cover a variety of topics, including thermodynamics, heat transfer, refrigerants, compressors, evaporators, condensers, and various refrigeration cycles. These MCQs can be used in academic settings, such as in exams or quizzes, or in industry settings, such as in job interviews or technician certification tests.

Examples of refrigeration MCQs could include questions such as:

Which of the following refrigerants has the highest Ozone Depletion Potential (ODP)?

a. R-22

b. R-134a

c. R-410a

d. R-123

The evaporator in a refrigeration system is responsible for:

a. Removing heat from the refrigerated space

b. Compressing the refrigerant gas

c. Condensing the refrigerant liquid

d. Controlling the flow of refrigerant through the system

The coefficient of performance (COP) of a refrigeration system is defined as:

a. The ratio of heat removed from the refrigerated space to the work input to the compressor

b. The ratio of the compressor discharge pressure to the evaporator pressure

c. The ratio of the condenser heat rejection to the compressor power input

d. The ratio of the refrigerant mass flow rate to the refrigerated space volume.

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Refrigeration and Air Conditioning MCQ Pdf Download