Experimental evaluation of R22 and R407C evaporative heat transfer coefficients in a vapour compression plant

The mean heat transfer coefficients of R22 and R407C in the coaxial counterflow evaporator (20 mm ID) of a refrigerating vapour compression plant have been experimentally measured. The experimental conditions under which heat transfer coefficients were determined reflect a typical working situation for small-scale refrigeration systems. The heat flux ranged from 1.9 to 9.1 kW/m2 and the mass flux was varied from 30 to 140 kg/m2 s. The results illustrate that the R22 heat transfer coefficient is always greater than that of R407C. Furthermore, a comparison carried out between the experimental data and those predicted by means of the most credited literature relationships showed a strongly overprediction for R407C coefficients.