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

3 is the correct Answer.

COP = (120-30)/30.
= 3.

The Answer should be 3.

120 - 30 = 90.
Cop=90/30=3 => answer.

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.

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.

This question also came in Isro exam.

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

So, the answer is 3.

To calculate the coefficient of performance (COP) of a refrigeration system, we use the formula:

{COP}_ {refrigeration}} = {Q_L}{W}

Where:

QL = Refrigeration effect = heat absorbed in the evaporator (in kW)
W = Work input to the compressor (in kW)
But in your question, the condenser rejects heat at the rate of 120 kW, and the compressor consumes 30 kW of power.
We know:

QH = QL + W.

Where:

(heat rejected by the condenser)
(compressor work)
So, the refrigeration effect is:

QL = QH - W
= 120 - 30 = 90{kW}

Now calculate the COP:
{COP} = {Q_L}{W} = {90}{30} = 3
So, the Final Answer: COP = 3.

120/30=4 this is the right answer.

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.