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

T2 is higher and T1 is lower temp considered here.

CP of heat pump = 1+ COP of ref.

D is for refrigeration. A is the correct answer.

If t2 is higher temp then B is correct.

The COP of refrigeration is {T1/(T2-T1)} so the cop of the heat pump is {T2/T2-T1)}.

Ref: R S Khurmi.

It depends on the temperature.

If T1 is greater than T2 then option A is correct.

And if T2 is greater than T1 then option D is correct.

According to me, Option A gives the COP of refrigerator.

COP 'for HP= (higher source temp)/(work input) --->(1)
Here,
If we consider T1- as lower sink temp.
T2- as higher source temp.

Therefore, work input = (T2-T1).
Hence COP should be from (1).
COP= T2 / (T2-T1).-->Ans D is correct.

Now, think about Option. A.
Here,
If we consider T2- as lower sink temp
T1- as higher source temp.
Work input should be (higher temp - lower temp) = (T1-T2),
Hence COP should be from (1),
COP = T1 / (T1 - T2).

But they have given it as a WD= (T2 - T1) which is not possible.
Hence option (A) is incorrect.