Refrigeration And Air Conditioning MCQ Questions & Answers | Mechanical Engineering Page-1 section-2

Section 1 Section 2 Section 3

1.
The lowest thermal diffusivity is of

A. Iron

B. Lead

C. Aluminium

D. Rubber

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2.
The central air conditioning system has ___________ overall efficiency as compared to individual systems.

A. Same

B. Lower

C. Higher

D. None of these

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3.
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

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4.
The vapour compression refrigerator employs the following cycle

A. Rankine

B. Carnot

C. Reversed Rankine

D. Reversed Carnot

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Answer & Solution

Answer: Option D

Solution:

The vapor compression refrigeration cycle employed by a typical refrigerator is a Reversed Rankine cycle. The Rankine cycle is commonly used in thermodynamic systems, especially in power plants, to convert heat energy into mechanical work. However, in a refrigeration system, the Rankine cycle is reversed to create a cooling effect.

The basic components of a vapor compression refrigeration system include a compressor, a condenser, an expansion valve, and an evaporator. Here's how the Reversed Rankine cycle works in a refrigerator:

1. Compression: The low-pressure, low-temperature vapor from the evaporator is compressed by the compressor, increasing its pressure and temperature.

2. Condensation: The high-pressure, high-temperature vapor is then condensed to a liquid in the condenser, releasing heat to the surroundings.

3. Expansion: The high-pressure liquid refrigerant passes through an expansion valve, where its pressure and temperature drop significantly, causing it to partially vaporize.

4. Evaporation: The low-pressure, low-temperature vapor-liquid mixture enters the evaporator, where it absorbs heat from the refrigerated space, cooling it down.

Option A: The Rankine cycle is a thermodynamic cycle used in power plants, not refrigeration systems.
Option B: The Carnot cycle is a theoretical thermodynamic cycle that represents the maximum possible efficiency of a heat engine or refrigerator, but it is not typically used in practical refrigeration systems.
Option D: The Reversed Carnot cycle is a conceptually similar cycle to the Reversed Rankine cycle, but the Rankine cycle is more commonly associated with vapor compression refrigeration.

Therefore, the correct answer is Option C: Reversed Rankine, as it represents the cycle employed by a vapor compression refrigerator to provide cooling.

5.
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

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6.
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

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7.
The thermostatic expansion valve is used in ________ type of evaporators.

A. Flooded

B. DX coil

C. Dry

D. None of these

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8.
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

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9.
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

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10.
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

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Refrigeration And Air Conditioning MCQ Questions & Answers | Mechanical Engineering

1. The lowest thermal diffusivity is of

Answer & Solution

2. The central air conditioning system has ___________ overall efficiency as compared to individual systems.

Answer & Solution

3. For air conditioning the operation theater in a hospital, the percentage of outside air in the air supplied is

Answer & Solution

4. The vapour compression refrigerator employs the following cycle

Answer & Solution

5. 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

Answer & Solution

6. During heating and humidification, the final relative humidity of air

Answer & Solution

7. The thermostatic expansion valve is used in ________ type of evaporators.

Answer & Solution

8. 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

Answer & Solution

9. A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be

Answer & Solution

10. The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.

Answer & Solution

Read More Section(Refrigeration and Air Conditioning)

1.
The lowest thermal diffusivity is of

2.
The central air conditioning system has ___________ overall efficiency as compared to individual systems.

3.
For air conditioning the operation theater in a hospital, the percentage of outside air in the air supplied is

4.
The vapour compression refrigerator employs the following cycle

5.
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

6.
During heating and humidification, the final relative humidity of air

7.
The thermostatic expansion valve is used in ________ type of evaporators.

8.
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

9.
A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be

10.
The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.