A commercial refrigerator operates with R - 12 between 1.2603 kgf / cm2 and 13.9272 kgf/ cm2. The vapour is dry and saturated at the compressor inlet. Assuming isentropic dry and saturated at the compressor inlet. Assuming isentropic compression determine the theoretical COP of the plant. The isentropic discharge temperature is 64.860C. If the actual COP of the plants is 80% of the theoretical, calculate the power required to run the compressor to obtain a refrigerating capacity of 1 ton. The properties of R - 12 are given below for reference. If the liquid is sub-cooled through 100 after condensation calculate the power required.
|
Saturation
Temp.
oC
|
Saturation pressure kgf/cm2
|
Enthalpy
kcal/kg
|
Entropy
kcal / kg oC
|
|
hf
|
hg
|
sf
|
sg
|
|
-25
|
1.2603
|
3.19
|
42.17
|
0.0132
|
0.1703
|
|
55
|
13.9272
|
23.00
|
50.11
|
0.0779
|
0.1636
|
|
Properties of superheated R-12
|
|
Temp
0C
|
Pressure
kgf / cm2
|
h
kcal / kg
|
s
kcal / kg0C
|
|
64.86
|
13.9272
|
52.684
|
0.1703
|
Assume specific heat of liquid to be 0.252 kcal / kg0C.