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Refrigeration & Air Conditioning Mcqs

Q:

If the Coefficient of performance of a heat pump is 5, then what is the value of the Coefficient of performance of the refrigerator operating under the same conditions?

A) 4 B) 6
C) 0.2 D) 3
 
Answer & Explanation Answer: A) 4

Explanation: Not available for this question

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1624
Q:

Find out the value of C.O.P. for the given values of enthalpies.
h1 = 1126.25 kJ/kg
h4 = 250.25 kJ/kg
W = 120 kJ/kg

A) 5.3 B) 6.3
C) 7.3 D) 8.3
 
Answer & Explanation Answer: C) 7.3

Explanation: Refrigerating effect = h1 ? h4 = 1126.25 ? 250.25 = 876 kJ/kg
Work = 120 kJ/kg
C.O.P. = Refrigerating effect / Work done
= 876 / 120
= 7.3.

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1296
Q:

What is the value of Refrigeration effect if m1 = 4 kg/min, and enthalpies for the point 1, 2, 4, 5, 9 are 1350, 1550, 1480, 1620, and 280 kJ/kg. If the refrigeration effect is 4280 kJ/min and work done is 15 kW, then what is the value of C.O.P.?

A) 4.85 B) 5.50
C) 4.75 D) 6.00
 
Answer & Explanation Answer: C) 4.75

Explanation: Given: m1 = 4 kg/min
h1 = 1350 kJ/kg
hf9 = h10 = 280 kJ/kg
h2 = 1550 kJ/kg
h4 = 1480 kJ/kg
h5 = 1620 kJ/kg
As, enthalpies of all points is given but it is a redundant data cause direct values of refrigeration effect and work is given, hence C.O.P. can be found easily.
Refrigeration effect = m1 (h1 – h11)
= 4280 kJ/min
Work = 15 kW = 900 kJ/min
C.O.P. = Refrigeration effect / Work
= 4280 / 900
= 4.75.

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811
Q:

In transport aviation, the air conditioning systems are based on ______ cycle.

A) Reversed Carnot cycle B) Reversed Brayton cycle
C) Reversed Joule’s cycle D) Otto cycle
 
Answer & Explanation Answer: B) Reversed Brayton cycle

Explanation: It is because in vapor-cycle the disadvantage was that due to the leakage loss of fluid it would cause the aircraft to be completely without cooling.

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727
Q:

What is the value of Refrigeration effect if m2 = 2 kg/min, m3 = 0.8 kg/min and enthalpies for the refrigerant at saturated vapor and saturated liquid line are 1420 and 1260 kJ/kg?

A) 192 B) 194
C) 196 D) 129
 
Answer & Explanation Answer: A) 192

Explanation: Not available for this question

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726
Q:

The C.O.P. of reverse Carnot cycle is most strongly dependent on which of the following?

A) Evaporator temperature B) Condenser temperature
C) Specific heat D) Refrigerant
 
Answer & Explanation Answer: A) Evaporator temperature

Explanation: The C.O.P in the reverse Carnot cycle generally depends on the higher of the two temperatures, as it is located in the numerator of C.O.P equation and responsible directly for increase or decrease in C.O.P.

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671
Q:

What is the main function of an expansion valve?

A) Reduce the refrigerant pressure B) Maintain high and low side pressures
C) Protect evaporator D) Control the velocity of flow of refrigerants
 
Answer & Explanation Answer: B) Maintain high and low side pressures

Explanation: Expansion valve mainly increases or decreases the flow of refrigerants, which directly affects the increase and decrease in the pressures.

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566
Q:

The COP of refrigerator may be improved by _________

A) decreasing the higher (T2) as well as the lower (T1) temperature B) decreasing the higher (T2) temperature and increasing the lower (T1) temperature
C) increasing the higher (T2) as well as the lower (T1) temperature D) keeping the higher (T2) temperature the same while decreasing the lower (T1) temperature
 
Answer & Explanation Answer: B) decreasing the higher (T2) temperature and increasing the lower (T1) temperature

Explanation: Not available for this question

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