Mechanical Engineering

Question: A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be
[A].

1.33

[B].

2.33

[C].

3.33

[D].

4.33

Answer: Option B

Explanation:

No answer description available for this question.

Question: 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].

l00 kJ/kg

[D].

125 kJ/kg

Answer: Option B

Explanation:

No answer description available for this question.

Question: A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
[A].

1 kW

[B].

2 kW

[C].

3 kW

[D].

4 kW

Answer: Option D

Explanation:

No answer description available for this question.

Question: Which of the following represents a heat pump?
[A].

[B].

[C].

[D].

Answer: Option B

Explanation:

No answer description available for this question.

Question: 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

Explanation:

No answer description available for this question.

Question: The capacity of a domestic refrigerator is in the range of
[A].

0.1 to 0.3 TR

[B].

1 to 3 TR

[C].

3 to 5 TR

[D].

5 to 7 TR

Answer: Option A

Explanation:

No answer description available for this question.

Question: The C.O.P. of a Carnot refrigerator in winter will be __________ as compared to C.O.P. in summer.
[A].

same

[B].

lower

[C].

higher

Answer: Option C

Explanation:

No answer description available for this question.

Question: A one tonne refrigerating machine means that
[A].

one tonne is the total mass of machine

[B].

one tonne refrigerant is used

[C].

one tonne of water can be converted into ice

[D].

one tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min

Answer: Option D

Explanation:

No answer description available for this question.

Question: One tonne of refrigeration (1TR) means that the heat removing capacity is
[A].

21 kJ/min

[B].

210 kJ/min

[C].

420 kJ/min

[D].

620 kJ/min

Answer: Option B

Explanation:

No answer description available for this question.

Question: A refrigeration system
[A].

removes heat from a low temperature body and delivers it to a high temperature body

[B].

removes heat from a high temperature body and delivers it to a low temperature body

[C].

rejects energy to a low temperature body

[D].

none of the above

Answer: Option A

Explanation:

No answer description available for this question.