The Effect Of The Fin Position And Rayleigh Number On Natural Convection In A Differentially Heated Cavity

Natural convection is extensively present in nature and industry. In particular, due to its considerable applications in the industrial equipment, natural convection in a differentially heated cavity is paid increasing attention. Since the enhancement of heat transfer through the cavity is of significance in industry, more investigators have carried out the studies of the approach to enhance or depress heat transfer through the cavity. It has been demonstrated that placing a fin on the sidewall of a differentially heated cavity is an appropriate method to change heat transfer through the cavity. Accordingly, the studies of the transient flow around the fin have been conducted over the last decade. However, the literature review about the flow around the fin shows that the effect of the fin’s height and material on natural convection in and heat transfer through the cavity in a range of high Rayleigh numbers is unclear. This motivates the present study, particularly under consideration of its practical significance in industry.In this study, a great number of numerical simulations of natural convection in the cavity with an adiabatic or a conducting fin at different heights over a range of high Rayleigh numbers have been performed. The present results show that the fin’s height and material may change transient flows and the development of natural convection from the initial stage to the quasi-steady stage as well as in turn heat transfer through the cavity. Particularly, the change of the fin height may induce different travelling waves downstream of the fin and corresponding heat transfer; that is, the flow around the fin at a lower height may disturb stronger travelling waves downstream and in turn enhance heat transfer. Additionally, in comparison with an adiabatic fin, a conducting fin may also generate stronger perturbations into the thermal boundary layer downstream of the fin. Similar to the cases without a fin, as the Rayleigh number increases, travelling waves in the thermal boundary layer downstream of the fin become stronger and heat transfer through the cavity is enhanced. The dimensionless heat transfer rate (Nu) is approximately dependent on Ra1/4(the power of the Rayleigh number slightly changes with the fin height).Although the effect of the fin height and material on the development of natural convection in the cavity has been observed and the features of natural convection and heat transfer dependent on the dimensionless parameter have been quantified, it is still necessary to perform further theoretical analysis and experiments in order to validate the present numerical simulations.