An experimental investigation and modelling of flow boiling heat transfer of isobutane-compressor oil solution in a horizontal smooth tube

• Isobutane-compressor oil solution local boiling heat transfer in a tube is studied.
• A boiling of refrigerant-oil solution in a tube was at stratified flow conditions.
• Heat transfer depends on oil admixture concentration, heat flux and flow rate.
• Increase in vapor quality decreases local boiling heat transfer coefficients.

Experimental results of local heat transfer coefficients for the boiling of working fluids (solutions of R600a with mineral naphthenic oil ISO VG 15) in a smooth tube with a small diameter (5.4 mm) are presented. The experiments have been performed in the following ranges: for the inlet pressure from 65.7 kPa to 82.2 kPa, for the heat flux from 2500 to 3300 W m−2, and for the mass velocity of the working fluid from 11.90 to 15.99 kg m−2 s−1). The quantitative estimation in reduction of the heat transfer coefficient of the wetted surface in the evaporator at a high oil concentration in the mixture is examined. The influence of heat flux and mass velocities on the values of the local heat transfer coefficients is analyzed. The equation for the modelling of the local heat transfer coefficient for boiling of an isobutane/compressor oil solution flow in the tube is suggested.