Investigation of heat transfer enhancement by electrohydrodynamics in a double-wall-heated channel

Abstract

In this study, heat transfer enhancement by electrohydrodynamics (EHD) in a rectangular double-wall-heated channel with an emitting electrode pair is investigated. The mechanism of EHD-enhanced heat transfer in double-wall-heated channels is different from that in single-wall-heated counterparts. An advantageous electrode arrangement in which one electrode impinges on the top wall and the other one impinges on the bottom wall is proposed. Furthermore, partially double-wall-grounded pattern is also employed. Based on the above superior design, the heat transfer enhancement level by EHD is dramatically improved, which is enhanced by 166.4% for the top wall and 242.7% for the bottom wall compared with those without EHD effect. The mechanism can be attributed to eliminating the so-called negative effect of “extra electric body force” in the channel and removing the “barrier effect” between the bulk flow and the corona jet-induced vortex. Besides, the effects of longitudinal position of the electrode pair (d) and the gap between two electrodes (l) are also examined. It is found that heat transfer enhancements for the top and the bottom wall both decrease with d. It is also observed that as l increases, enhanced level for the top wall is firstly increased and then gradually reduced, while it is monotonically enhanced for the bottom wall. The effects of d and l are determined by combination of the negative effect of “extra electric body force” in the channel and the vortex temperature.