An experimental investigation of the effect of oil on convective heat transfer and pressure drop of a HFC-32/HFC-125 mixture

The heat transfer coefficients and pressure drops of HCFC-22 and a 50% mass mixture of HFC-32/HFC-125 were experimentally measured under flow boiling conditions in a smooth tube. The refrigerants were flowed through an 8 mm diameter smooth tube at mass fluxes of 277, 434, 520 and 700 kg/m;The heat transfer coefficients for HCFC-22 increased with quality, mass flux and heat flux. The heat transfer coefficients for HFC-32/HFC-125 often decreased at low qualities and increased with quality at high qualities.;The pressure drop increased with quality and mass flux for both refrigerants. The heat transfer had a minimal effect upon pressure drop. HFC-32/HFC-125 had a lower pressure drop than HCFC-22 for all conditions. The addition of oil increased the pressure drop.;A pressure drop correlation and heat transfer correlation were developed for HFC-32/HFC-125.