Flow boiling heat transfer characteristics and pressure drop of R290/oil solution in smooth horizontal tubes

Abstract

R290/oil solution is a potential working pair of absorption refrigeration systems. This paper presents experimental results of flow boiling heat transfer coefficients of R290/oil solution in smooth horizontal tubes with inner diameters of 4, 6 and 8 mm. The R290 mass concentration of the solution at the inlet of the test section is about 15%. Mass flux, heat flux and boiling temperature are in the ranges of 221–387 kg/m2 s, 14–27 kW/m2 and 59–71 °C, respectively. The effects of mass flux, heat flux, exit vapor quality, boiling temperature and inner diameter on flow boiling heat transfer coefficients have been investigated. Results show that when compared with other operating parameters, the variation of the solution properties triggered by boiling temperature has the most obvious influence on boiling heat transfer coefficient. And the decrease of inner diameter of the test section will be beneficial to the flow boiling heat transfer. The present experimental results are also compared with experimental data from other literature as well as predicted values of various existing correlations. It is found that the correlation of Gungor and Winterton has the highest precision, with a mean deviation of ±15.75%. Pressure drops of the solution side are also measured under different test conditions. The results of the present study will be of great help to the application of R290/oil solution and the design and optimization of finned tube heat exchangers (generators) in absorption refrigeration systems.