Natural Convection Analysis Around Elliptical Shapes With Sinusoidal Heat Flux Using CFD

Heat transfer is important as technology becomes more compact, thereby increasing the heat flux and consequently the need for cooling. This paper will investigate natural convection on an elliptical shape with sinusoidal heat flux input. Natural convection was analysed using CFD simulations on an ellipse, with minor- to major axis ratio b/a=0.6 and an inclination angle of α=90°. The sinusoidal heat flux was non-dimensionalised by a modified Grashof number Gr*=g · β · (∂T/∂n) · Lc^4/v^2 with a mean value of 2×10^7, amplitude of up to 2×10^7, and dimensionless angular frequency ω*=ω · L^2/v=24, 36, and 72. All simulations were made with a Prandtl number of Pr=7.0. To ensure reliable results a Grid Convergence Index analysis was carried out. Validation was made by comparing the obtained surface averaged Nusselt numbers to previous studies and results from performed experiments. An experiment using Particle Image Velocimetry, PIV, measured the flow field around an ellipse. The results from the sinusoidal heat flux showed that the difference in accounting for the sinusoidal Grashof function was up to 10% for the time-surface averaged temperature and time-surface averaged Nusselt number. Generally, the amplitude would increase the temperature, while the effect of the dimensionless angular frequency was dependent on the given amplitude.