Experimental investigation on convective heat transfer enhancement by EHD in wire to plate configuration

Abstract

The purpose of this study was to experimentally investigate the enhancement of forced convection heat transfer by corona wind in a channel scaled to potential future drying systems. An experimental rig was designed to investigate the thermal and dynamic effects of electro-hydrodynamic (EHD) induced air flow on the grounded bottom wall. The primary air flow, blown into the channel at controlled temperature and velocity, was disturbed by EHD secondary flow generated by a wire electrode. Using IR imaging, the heat transfer exchange at the wall was calculated in several configurations (i.e. electrodes location, wire-electrode to plate distance, applied voltage, primary air flow velocity), allowing the selection of optimal configurations according to the objective of minimum energy consumption or homogeneous transfer. Particle Image Velocimetry (PIV) characterization conducted on some configurations highlighted the vortices generated by the combination of the secondary and the primary air flows. Analysis of the flow patterns allowed to explain the enhancement of the local and average heat transfer coefficients. Higher enhancement could be obtained in the cross-wire configuration but led to heterogeneous treatment. For a more homogeneous one, the longitudinal wire configuration should be preferred thanks to the development of contra-rotating vortices moving in the channel.