The effects of applying DC high voltage electric fields on two-phase flow regime transitions for flowing refrigerant HFC-134a were visualized using a high speed camera. The viewing test section was made of 10 mm inner diameter quartz tube with a 3.18 mm diameter charged electrode placed along the center of the tube. The quartz tube was coated with an electrically grounded transparent conductive film of Tin Oxide. The experiments were performed for mass flux (55 kg/m2s < G < 263 kg/m2s), quality (20% < x < 80%) and applied voltage (0 kV < V < 8 kV). The flow regime transitions depend on the flow regime prior to applying the EHD. For stratified flow, EHD increases the interfacial instabilities and causes liquid extraction to the upper section of the tube. When the flow regime is initially annular flow, EHD increases the uniformity of the annular film by extracting liquid from the thicker liquid regions into the vapor core.

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