Question

. An ideal vapor compression refrigeration cycle operates with a condenser pressure of 900 kPa. The temperature at the inlet to the compressor is -5oC. If this device operates using R134a as the working fluid, calculate the actual COP of this device as well as the maximum theoretical COP.

Answer 1

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