Application of Electric Field to Developing Falling Films using Wire-Plate Electrode Configuration- An Experimental Study

Experimental investigation of Electrohydrodynamic developing falling film flow of transformer oil has been conducted within an inclined rectangular channel and hydrodynamic characteristics of the flow have been revealed. The electric field has been generated by five overhead thin wire electrodes connected to the positive high DC voltage on the air and the grounded plate electrodes which are placed upon the floor of the channel. It is the first time that the wavy behavior on a liquid falling film's interface has been created by this electrode configuration. A non-intrusive method has been used to measure the local flow structure by a high-speed camera, then statistical characteristics of the wavy falling film have been computed by image processing of the captured video frames. By applying ۱۳-۱۶ kV to the wire electrodes, the influence of EHD force on the wavy behavior of falling film has been conducted for Reynolds number ۱۰-۱۲۰ in the laminar-wavy regime at three different inclination angles ۱۵◦, ۳۰◦ and ۴۵°. The vertical distance of the high-voltage wire electrodes to ground electrodes has been set to ۱۴ mm. The liquid velocity, film thickness, and wave frequency have been measured for non-electrified and electrified falling film, and their results have been evaluated with other experimental studies and an acceptable agreement has been obtained. The results indicate that the proposed HV wire-grounded plate electrode configuration in this study does not disturb the original structure of the falling film and by intensifying the wavy behavior of laminar falling film can either suppress or enhance heat/mass transfer rate. The effects of the applied voltage on the frequency, velocity and film thickness of the falling liquid film have been also discussed in detail.

کلیدواژه ها:

EHD ، Falling film ، Wire ، Dielectric ، plate electrode ، Image processing