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

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

[A]. 1/4
[B]. 1/3
[C]. 3
[D]. 4

Answer: Option D

Explanation:

No answer description available for this question.

Gaurav said: (Sep 4, 2014)  
C.O.P = favourable effect/work input = 120/30 = 4.

Here favourable effect is rejection of heat.

Indra Bhushan Rai said: (Oct 6, 2014)  
Refrigeration effect = 120-30 = 90.

cop = 90/30 = 3.

Ankusb said: (May 9, 2016)  
I agree with you @Indra 3 is the correct answer.

Jignesh said: (Jul 25, 2016)  
cop = R.E/WORK = 90/30 = 3.

Jnk said: (Aug 11, 2016)  
cop = ref effect / work done.
= 120 - 30 / 30.
= 3.

Ajith said: (Sep 19, 2016)  
C.O.P = heat/workdone,

=> 120/30,

=> 4.

Mehul J said: (Dec 15, 2016)  
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.

Lucky Patel said: (Dec 29, 2016)  
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.

Rakesh Thakur said: (Jan 11, 2017)  
cop = out put /input.
energy out /input.
120/30.

Yatendra said: (May 23, 2017)  
Yes, I agree cop = 3.

Manash said: (Jul 20, 2017)  
The answer is (c) 3.

Anand Kumar Singh said: (Jul 25, 2017)  
3 is the correct answer.

Prabhat Swain said: (Aug 16, 2017)  
This question also came in Isro exam.

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

So, the answer is 3.

Prabhat Swain said: (Aug 16, 2017)  
@Rakesh Thakur.

Output/input not COP.
This is efficiency.

COP is the reciprocal of efficiency.

Lalit Kumar said: (Aug 31, 2017)  
120-30 = 90.
Cop=90/30=3 => ans.

Vishnu P said: (Nov 23, 2017)  
Answer will be 3 because here 120 is heat rejected not heat extracted.

Vishnu said: (Aug 13, 2018)  
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.

Zeeshan said: (Dec 17, 2018)  
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.

Swagat said: (Jul 30, 2019)  
COP = (120-30)/30.
= 3.

S Kamran said: (Sep 28, 2019)  
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.

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