The refrigerant R-12 is sub-cooled by 5˚C before throttling and the vapour is superheated by 2°C before leaving the evaporator. Assuming a twin cylinder single acting compressor running at 1000 RPM with L:D ratio of 1:5. Calculate:

i. COP of system

ii. Specific power required

iii. Diameter

iv. Stroke of compressor having volumetric efficiency of 0.945.

Draw P-h and T-s diagram.

Subject : Refrigeration and Air Conditioning

Topic : Vapour Compression Refrigeration System

Difficulty : Medium

Given:
Q = 12 TR ;$T_1’=-8°C = - 8 + 273 = 265 K ;T_2’= 30° C = 30 + 273 =303 K ;T_3’-T_3=5° C;$
$T_1= -2° C = -2+273 = 271 K ;h_{f1}=28.72kJ/kg ;h_{f3}’=64.59 kJ/kg ; $
$h_1’= 184.07 kJ/kg ;h_2’= 199.62 kJ/kg ;s_{f1}= 0.1149 kJ/kg K ;s_{f3}=0.2400 kJ/kg …