Thermal Engineering Mcqs

Q:

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 condenser D) pressure in the evaporator
 
Answer & Explanation Answer: A) degree of superheat at exit from the evaporator

Explanation: The thermostatic expansion valve operates on the changes in the degree of superheat at exit from the evaporator. Thermostatic expansion valves are usually set for a superheat of 5° C for better efficiency of the refrigeration cycle.

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20
Q:

The low-side float valve is located between the condenser and evaporator.

A) True B) False
 
Answer & Explanation Answer: B) False

Explanation: The low-side float valve is located in the low pressure side i.e. between the evaporator and the compressor suction line. Whereas the high side float valve is located in the high pressure side i.e. between the condenser and evaporator.

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25
Q:

Thermostatic expansion valves are usually set for a superheat of?

A) 10°C B) 5°C
C) 8°C D) 15°C
 
Answer & Explanation Answer: B) 5°C

Explanation: Thermostatic expansion valves are usually set for a superheat of 5°C for better efficiency of the refrigeration cycle.

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26
Q:

Which one of the following is also known as a constant superheat valve?

A) Capillary tube B) Hand-operated expansion valve
C) Thermostatic Expansion valve D) Low side float valve
 
Answer & Explanation Answer: D) Low side float valve

Explanation: Thermostatic expansion valve is also called a constant superheat valve because it maintains a constant superheat of the vapor refrigerant at the end of the evaporator coil, by controlling the flow of liquid refrigerant through the evaporator.

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31
Q:

Capillary tube, as an expansion device is used in?

A) Water coolers B) Domestic refrigerators
C) Room air conditioners D) All of the mentioned
 
Answer & Explanation Answer: D) All of the mentioned

Explanation: The capillary tube as an expansion device is used in small capacity hermetic sealed refrigeration units such as in water coolers, domestic refrigerators and room air conditioners, etc.

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17
Q:

Which of the following is not an advantage of capillary tube?

A) The cost of capillary tube is less B) A high starting motor is not required
C) No receiver is needed D) A capillary tube designed for a specific condition will also work efficiently for other conditions
 
Answer & Explanation Answer: D) A capillary tube designed for a specific condition will also work efficiently for other conditions

Explanation: A capillary tube designed for a specific condition will not work efficiently for other conditions as the length is directly and inner diameter is indirectly proportional to the frictional resistance. The longer the tube and smaller the diameter, greater is the pressure drop created in the refrigerant flow.

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42
Q:

The expansion device is placed between which two components?

A) Condenser and evaporator B) Compressor and condenser
C) Evaporator and compressor D) Receiver and evaporator
 
Answer & Explanation Answer: D) Receiver and evaporator

Explanation: The expansion device is placed between receiver (containing liquid refrigerant at high pressure) and evaporator (containing liquid refrigerant at low pressure).

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22
Q:

The expansion device used with flooded evaporators is known as expansion valves.

A) True B) False
 
Answer & Explanation Answer: B) False

Explanation: The expansion device used with flooded evaporators is known as float valves and the expansion device used with dry expansion evaporators are called expansion valves.

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