Abstract: This paper investigates the natural convection heat transfer process under the enhancement of an electric field using numerical simulation methods. It examines two heat transfer conditions: with the heated surface facing upwards and downwards. By comparing numerical results with experimental data, the study expands the computational scope, explores the heat transfer enhancement effects under different heat flux densities (4 000 W·m^-2, 5 000 W·m^-2, 6 000 W·m^-2, 7 000 W·m^-2, 8 000 W·m^-2), and voltage ranges (1 000 V to 8 000 V). Additionally, it contrasts the influence of the electric field on the flow field and convective heat transfer coefficients between the cases where the heated surface faces upwards and downwards. The research reveals that under the influence of an applied electric field, dielectric fluids generate dielectrophoretic forces that act in synergy with thermal buoyancy, driving fluid flow and altering its direction. Electroconvection not only enhances heat transfer but also modifies the velocity field of natural convection, thereby improving its heat transfer performance. Particularly, higher voltages demonstrate significantly better cooling effects compared to lower voltages. In the case where the heated surface faces upwards, the electric field force suppresses vertical thermal convection and alters the direction of the horizontal velocity field. Conversely, in the case where the heated surface faces downwards, the interaction between the electric field force and buoyancy accelerates fluid flow.