Enthalpy of Vaporization:
This must be as large as possible to reduce the area under superheat & the area reduction because of throttling. Also, the higher value of enthalpy of vaporization lowers the needed flow rate per ton of refrigeration.
Considering these three factors into account, the T-s & p-h diagrams of an ideal refrigerant would be as indicated in given (a) and 4.3 (b).
![1421_Enthalpy of Vaporization.png](https://www.expertsmind.com/CMSImages/1421_Enthalpy%20of%20Vaporization.png)
(a) T-S Plot of an Ideal Refrigerant (b) p-h Plot of an Ideal Refrigerant
Practically these properties are not found in any refrigerant. Therefore, a trade-off has to be done to attain as high a COP as possible.