properties of r-12
At -16C p=175.6 kPa , hf=185.2 KJ/kg hg=345.5 KJ/kg
At 27C p=686.7 kPa hg=364.2 KJ/kg
properties of r-134a
At -16C p=157.3 kPa ,hf=30.69 KJ/kg ,hg=240.87 KJ/kg
At 27C p=707.308 kPa ,hg=413.3 KJ/kg
By changing refrigerent evaporator pressure will reduce while
condensor pressure will increase.
Consider latent heat of vaporization of r-12 =160.3KJ/kg
prssure ratio with r-12=3.90
latent heat of vaporization of r134a =210.18
prssure ratio with r134a=4.5
COP is ratio of refrigerating effect to work required.
Now for r134a system refrigerating effect is more mean while
work input is more so COP may increase or decrease.
