Answer:
Actual COP = 5.368
Maximum theoretical COP = 6.368
Explanation:
Given - An ideal vapor compression refrigeration cycle operates with a condenser pressure of 900 kPa. The temperature at the inlet to the compressor is -5oC.
To find - If this device operates using R134a as the working fluid. Calculate the actual COP of this device as well as the maximum theoretical COP.
Proof -
Given that,
An ideal vapor compression refrigeration cycle operates with a condenser pressure of 900 kPa.
From Refrigerant 134-a Table
At T1 = -5°C
h1 = 247.505 KJ/kg
S1 = 0.93434 KJ/kg
At P2 = 900 KPa
S1 = S2
h2 = 274.679 Kj/Kg
h3 = h4 = 101.61 KJ/g
So,
Compressor work (Wc) = h2 - h1
= 274.679 - 247.505
= 27.174
⇒Compressor work (Wc) = 27.174 KJ/kg
Now,
Heat out (Qout) = h2 - h3
= 274.679 - 101.61
= 173.069
⇒Heat out (Qout) = 173.069 KJ/kg
Now,
Heat input (Qin) = h1 - h4
= 274.505 - 101.61
= 145.895
⇒Heat input (Qin) = 145.895 KJ/kg
So,
Actual COP at the refrigerator is -
(COP)R = (Qin)/(Wc)
= (145.895)/ (27.174)
= 5.368
⇒Actual COP = 5.368
Now,
Maximum theoretical COP is -
(COP) = (Qout)/(Wc)
= (173.069)/ (27.174)
= 6.368
⇒Maximum theoretical COP = 6.368
