# Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion

Discussion Forum : Heat Transfer, Refrigeration and Air Conditioning - Section 6 (Q.No. 1)
1.
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
1/4
1/3
3
4
Explanation:
No answer description is available. Let's discuss.
Discussion:
25 comments Page 1 of 3.

Zeeshan said:   5 years ago
Point to ponder is whether the COP of the heat pump is asked or COP of the Refrigeration system. The question doesn't define the fact categorically. Assuming heat pump answer is 4, of we assume COP of refrigeration system then given answer is wrong and it must be 3.

Lucky Patel said:   7 years ago
Answer should be 3.

Because the ratio of condenser heat rejection to power consumption is called co efficient of performance for the heat pump. And we have to find cop of refrigerator thus from equation
COP hp =COPr + 1.
Cop for refrigerator 3.

S Kamran said:   5 years ago
Answer will be 3..

120kw is heat rejected(not R.E)by the condenser that heat is the sum of Refrigeration effect(R.E)& The heat added by compressor work.. & COP= R.E/Work Input. So the final answer will be COP=(120-30)/30=3.
(1)

Vishnu said:   6 years ago
The answer is 3.

Here 120 is the heat rejected to the atmosphere, not the heat absorbed from the refrigerated space.

120 - 30 is the heat absorbed from the refigerated space.
The Work input is 30.

Mehul J said:   7 years ago
Heat rejected = Heat taken from Evaporator + heat rejected from compressor.

Here heat Rejected is given as summation of RE+ W ( Compressor).
Now COP = RE/Work.
= 120 - 30/30 = 3.

Swapnil Shelke said:   4 years ago
I also agree with the answer 3 as here COP of the refrigeration system is asked clearly here REFRIGERATING EFFECT is 90 and work input 30.
(1)

Prabhat swain said:   7 years ago
This question also came in Isro exam.

And answer key of ISRo shows the correct answer is 3.

So, the answer is 3.

Gaurav said:   10 years ago
C.O.P = favourable effect/work input = 120/30 = 4.

Here favourable effect is rejection of heat.

Prabhat swain said:   7 years ago
@Rakesh Thakur.

Output/input not COP.
This is efficiency.

COP is the reciprocal of efficiency.

Vishnu p said:   7 years ago
Answer will be 3 because here 120 is heat rejected not heat extracted.