Condensation heat transfer coefficients of the zeotropic refrigerant mixture R-22/R-142b in smooth horizonal tubes

Heat transfer coefficients during condensation of the zeotropic refrigerant mixture R-22 with R-142b are presented. Measurements were obtained at different mass fractions in a smooth horizontal tube. All measurements were conducted at a high condensing saturation pressure of 2.43 MPa, which corresponds to a condensation temperature of 60 degreesC for R-22. The measurements were taken in 8.11 mm inner diameter smooth tubes with lengths of 1 603 mm. The heat transfer coefficients were determined with the Log Mean Temperature Difference equations. It was found that at low mass fluxes, between 40 kg-m(-2).s(-1) to 350 kg.m(-2).s(-1), the refrigerant mass fraction influences the heat transfer coefficient by up to a factor of two. The heat transfer coefficients decrease as the fraction of R-142b is increased. At high mass fluxes, of 350 ka.m(-2).s(-1) and more the heat transfer coefficients were not strongly influenced by the refrigerant mass fraction. The average heat transfer coefficient decreased by only 7% as the refrigerant mass fraction changed from 100% R-22 to 50%/50% R-22/R142b. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.