Effect of external electrode arrangements on R-134a two-phase flow regimes in the presence of AC electric fields

In this study, two-phase flow regime redistribution in a horizontal tube within which two-phase flow of refrigerant R-134a is passing under the influence of high-voltage AC electric fields is experimentally investigated. The experimental study deals with the effects of external position for double electrodes, external arrangements for triple electrodes and using alternative refrigerant. A theoretical Steiner tube two-phase flow pattern map for external double electrode arrangement in the horizontal tube under flow conditions with mass fluxes of 30-530 kg/m(2) s, inlet qualities from 0% to 90% and fixed applied voltage of 9.8 kV is developed. The results show that by intensifying the applied electric field and increasing the vapor quality, the volume of the liquid splashed on the tube wall increases. It is found that electrode arrangements substantially affect on the two-phase flow pattern. Based on these results, because of the difference between the created electric field of the various electrode arrangements, the number of generated bubbles and their density in arrangement #2 is significantly less than arrangement #1. Also the results indicate that because of the uniformity of electric field, the number of the generated bubbles and their density in electrode arrangement #5 is more than all of the electrode arrangements. Eventually, the effect of using refrigerant R-600a rather than R-134a is studied. It was observed that because of low difference between liquid and vapor electric permittivity for R-600a, applying AC high-voltage on R-600a two-phase flow has not any impact on two-phase flow regime redistribution. (C) 2017 Elsevier Ltd. All rights reserved.