Effects of electrode location on EHD-enhanced natural convection in an enclosure

摘要

Numerical results are presented for natural convection in an enclosure under the influence of electric field. The geometry considered is a two-dimensional cavity with an aspect ratio of 5. The electrical field is generated by positive corona from an electrode wire changed with a high dc voltage. Three wire locations have been considered, which result in symmetric and non-symmetric electric fields. Numerical calculations have covered a wide range of parameters (i.e., V_o chemical bounds 12, 15 and 18 kV, 10~3 =< Ra =<10~6). In the presence of electric field, the flow and temperature fields may reach a steady, steady-periodic or non-periodic state. Flor low Rayleigh numbers, it is observed that the flow and temperature fields are basically oscillatory in nature. When the Rayleight number is sufficiently increased, a steady state may be reached. Due to the oscillaory flows, there is a significant increase in heat transfer. It is found that heat transfer ehancmenet increases with the applied voltage but decreases with the Rayleight number. In addition, it is found that heat transfer enhancement can be maximized by placing the electrode toward the leading edge of the heat transfer surface, that is, to perturb the thermal bounary alyer as early as it beins to develop.