EHD-Induced Flow and Heat Transfer in a Square Channel

Abstract

Induction of a fluid flow within a square channel using electrohydrodynamic (EHD) principles and consequent effects on heat transfer enhancement are examined using both experimental and numerical methods. Experiments are conducted first to provide important information for computing the electric field in the numerical study. EHD-induced flow in a square channel is investigated via experimentation. Electrode pins are flush mounted on the channel walls and charged with a high voltage. Three such configurations of the EHD gas pump are tested (with 4, 12, and 28 electrode pins, respectively) for a wide range of operating voltages starting from the corona threshold voltage up to 28 kV. Both corona current and corona wind velocity inside the channel are measured for operations using either positive or negative corona discharges. The performance of the EHD gas pump is then evaluated against that of conventional fans. The experimental results provide important insights for the optimal design of an EHD gas pump. A numerical model is developed based on the experimental study. The threedimensional governing equations for the electric, flow, and temperature fields are solved using the finite difference method. Corona-driven flow is calculated first, and its results are compared with the experimental data to validate the computational code. The numerical results enable vivid flow visualizations inside the channel, providing a great understanding of the development of the induced flow. With forced convection, the influence of electric field on the flow and temperature fields is investigated. Numerical calculations are performed on the EHD gas pump with all three electrode configurations at various applied voltages and a wide range of Reynolds numbers. The heat transfer enhancement and thermal hydraulic performance are then evaluated. The results of the numerical study show that EHD technique has a great potential for many engineering applications.