Interpreting R22 tables - advice sought

[solas]

Hello to all
I would appreciate your advice on a refrigeration problem.
I am working on a refrigeration assignment and would like a second opinion on the thermodynamic properties that I have selected from the tables.

The operating conditions are as follows;
Condensing temperature Tc: 30 degC
Evaporating temperature Te: 5 degC
Refrigerant type/tables: DuPont ***** R22. (T-22 SI units-kJ/kg)

Points on PH diagram:
a= hf Enthalpy of saturated liquid (kJ/kg)
b= hf Enthalpy of saturated liquid (kJ/kg)
c= hg Enthalpy of saturated vapour (kJ/kg)
d= h Enthalpy of superheated vapour (kJ/kg)

Values I got from the tables;
hf at Tc 30 degC = 236.6 (ha = hb = isenthalpic expansion) - page 5
hg at Te 5degC = 406.8 (hc) - page 4
h at Tc 30 degC / 1,200kPa = 422.9 9 (hd - isentropic compression) - page 14

Cooling COP = hc-hb / hd-hc
Substituting values
Ans. 10.57

The cop appears to be very high and I think it may be down to my incorrect interpretation of the tables. I would appreciate your comments on the accuracy of the above values and COP.

Your help would be greatly appreciated.
Thanks in advance.
　

[taz24]

Hello to all
I would appreciate your advice on a refrigeration problem.
Cooling COP = hc-hb / hd-hc
Substituting values
Ans. 10.57

The cop appears to be very high and I think it may be down to my incorrect interpretation of the tables. I would appreciate your comments on the accuracy of the above values and COP.

Your help would be greatly appreciated.
Thanks in advance.
　

I have just done 2 quick calcs using your figures.

1 with no superheat or subcooling = COP of 9.6

1 with 8 degC superheat and 5 degC subcooling = COP of 10.02

So your answer is not a million miles away.
But it does seem high.

taz.

.

[solas]

Hello Taz

Thanks for taking the time to compare the information. It will help me make further progress.
If you dont mind, I might request your opinion on a silmilar topic before I complete this project.

Thanks again