The two-phase heat transfer coefficient and pressure drop characteristics of refrigerants R22 and R407C (a mixture of R32/R125/R134a, 23%/25%/25%) within a smooth tube with a nominal diameter of 9.52mm are presented. The data were taken at two different evaporation pressures (600kPa and 680kPa, respectively). The mass flux was between 100 and 300kg/m2.s and the heat fluxes were between 6 and 14kW/m2. Experimental data were presented in the form of quasi-local heat transfer coefficients and frictional pressure gradients. The effects of heat flux, mass flux, and evaporation pressure on the heat transfer coefficients are also reported in the present investigation. It was found that the heat transfer coefficients for R407C are considerably lower than those for R22 (50% to 70% less), and the pressure drop of R407C is similar to that of R22 at low mass flux (G=100kg/m2.s) and 45% lower compared to R22 at a higher mass flux (G=300kg/m2.s).

KEYWORDS: year 1996, heat flow, heat transfer coefficient, refrigerants, R22, R407C, mixtures, R32, R125, R134a, comparing, pressure drop, properties, thermodynamics, friction, experiment, calculating