Convective boiling of pure and mixed refrigerants: An experimental study of the major parameters affecting heat transfer

An experimental study is carried out to investigate the characteristics of the evaporation heat transfer for different fluids. Namely, pure refrigerants fluids (R22 and R134a), azeotropic and quasi-azeotropic mixtures (R404A, R410A, 8507) and zeotropic mixtures (R407C and R417A). The test section is a smooth, horizontal, stainless steel tube (6 mm ID, 6 m length) uniformly heated by the Joule effect. The flow boiling characteristics of the refrigerant fluids are evaluated in 250 different operating conditions. Thus, a data-base of more than 2000 data points is produced. The experimental tests are carried out varying: (i) the refrigerant mass fluxes within the range 200-1100 kg/m(2) s; (ii) the heat fluxes within the range 3.50-47.0 kW/m(2); (iii) the evaporating pressures within the range 3.00-12.0 bar. In this study, the effect on measured heat transfer coefficient of vapour quality, mass flux, saturation temperature, imposed heat flux, thermo-physical properties are examined in detail. (C) 2007 Elsevier Ltd. All rights reserved.