The present article reports on the results of experimental research carried out on compact plate heat exchangers, currently used as evaporators and condensers in refrigeration loops. The research was aimed at getting information on the thermal efficiency of the heat exchangers, under reference commercial conditions, when using new ozone-friendly refrigerants to replace CFCs and HCFCs. Specifically, the influence of some thermal-hydraulic parameters on the heat flux and the overall heat transfer coefficient are investigated for evaporators, using R134a, R407C, and R410A, three fluids proposed to replace R22, and HCFC, currently the most common refrigerant used in residential and commercial air conditioning equipment. Moreover, in this article a new thermodynamic method has been applied with the purpose of defining the saturation temperature and investigating the other main parameters for mixtures in the two-phase region for the fluids R407C and R410A, which are blends of, respectively, three and two pure refrigerants.