Numerical investigation of the electro-thermo-convection heat transfer enhancement in a square annulus involving a heated square block

This study numerically investigated the heat transfer enhancement in a square annulus composed of a positive electrode on the inner surface square cylinder walls of dimension ratio 0.125∼0.6 (i.e., hot walls), while the enclosure walls (i.e., cold wall) were electrically grounded. A parametric investigation was conducted under various underlying thermal Rayleigh (Ra = 10³–8×10⁵) and electric Rayleigh (T = 0–2000). Just as the conduction-to-convection transition in pure thermal convection of an annulus is significantly affected by the annulus dimension ratio, the transition of thermal convection to electro convection has also been revealed to be greatly affected by the annulus dimension ratio. Furthermore, the heat transfer enhancement by the electro convection did not show a monotonic increase with the dimension ratio; instead, the dimension ratio 0.25 showed the best heat transfer enhancement of around 1200% at Ra = 10³ and T = 2000. This means that optimizing the gap size between electrodes can improve heat transfer in a specific target application. The related flow field and Nusselt number changes are presented in detail.