Condensation of a Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli With an Enhanced Inner Tube

Local heat transfer and pressure drop measurements are made during condensation of a nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double-tube condensers. The inner tube is a 19.1-mm-o.d. corrugated tube with copper wire fins soldered on the outer surface. The outer tubes are smooth tubes with different i.d. of 29.9 and 25.0 mm. The heat transfer coefficient based on the bulk-vapor to wall temperature difference is considerably smaller for R114/R113 mixtures than for pure R113. An empirical equation for the vapor phase mass transfer coefficient is derived, in which the dimensionless parameters are introduced on the basis of the previous results for turbulent single phase flow in smooth and rough tubes with and without surface suction. The measured condensation heat transfer coefficients for R114/R113 mixtures are correlated by the present model to a mean absolute deviation of 14.3 percent.