2-PHASE HEAT-TRANSFER CHARACTERISTICS FOR R-22 R-407C IN A 6.5-MM SMOOTH TUBE/

Two-phase friction and heat transfer characteristics for R-22/R-407C i nside a 6.5-mm smooth tube are reported in this study, The hear transf er results for G = 100 and 400 kg/m(2) s were reported in the present study, and the adiabatic frictional pressure drop was recorded in the range of 100 to 700 kg/m(2) s, It is found that the development of flo w pattern for R-407C Falls behind R-22. This may explain the lower pre ssure drops for R-407C. The major heat transfer mechanism at low mass flux is nucleate boiling, and virtually becomes the convective evapora tion as mass flux increase to G = 400 krg/m(2) s, Meanwhile, the reduc tion of heat transfer coefficients for R-407C mixtures are especially profound at low mass flux, and The reduction of heat transfer coeffici ent decreases with the increase of mass flux. (C) 1997 by Elsevier Sci ence Inc.