Flow and heat transfer characteristics of corona wind in two symmetric divergent fins

Abstract

A wire electrode is placed in a heat sink featuring two symmetric divergent fins to constitute an electrohydrodynamic (EHD) device for enhancing convection heat transfer. The wire electrode has three diameters of 0.08 mm, 0.1 mm, and 0.12 mm and six positions on the centerline of the two fins, respectively. The experimental results show that the heat transfer coefficient is significantly improved with the presence of EHD. Moreover, a finer wire achieves a better heat transfer enhancement. As the wire moves towards the wider opening of the fins, the corona current declines, while the heat transfer coefficient increases first and then decreases. A two-dimensional numerical model is developed to explore the heat transfer mechanism. The simulation predicts the wire position corresponding to the inflection point of the heat transfer coefficient. The inflection point can be explained by the airflow field characteristics. Two vortexes are created by the EHD force in the flow field, and their size, strength, and position vary with the wire position. This leads to different air convection and entrainment at different wire positions, thus affecting the heat transfer performance. In addition, the electric field distribution is also obtained numerically. The corona current and current density agree well with our experiment and the empirical formula, respectively.