Numerical investigation of EHD effects on heat transfer enhancement and flow pattern of R-134a two phase flow

In this paper the effects of electrohydrodynamics (EHD) on heat transfer enhancement and flow pattern of R134a two-phase mixture, flowing in a horizontal tube, were numerically investigated. A uniform DC electric field was applied through a circular stainless steel rod along the centerline of tube, while the tube was considered as a grounded electrode. The simulations, in order to investigate the EHD mechanism, were performed for a constant heat flux 2000 W/m(2), voltages between 0 and 5 kV, inlet volume fractions 65% and 85%, mass fluxes from 30 kg/m(2)s to 50 kg/m(2)s and electrode diameters between 1.57 mm and 2.4 mm. These flow conditions correspond to stratified flow. The flow regime redistributions under the applied electric field was obtained. The results show that the steady state condition was occurred at the time about 900 ms. According to the results, enhancement ratio is directly proportional to voltage, and it is reversely proportional to electrode diameter, mass flux and inlet volume fraction. (C) 2016 Elsevier B.V. All rights reserved.