Geriye Dönük Adım Akışında Adım Geometrisinin Isı Transferi ve Akış Yapısı Üzerindeki Etkisinin İncelenmesi

Abstract

In many engineering applications such as gas turbine engines, burners, heating and cooling systems, separation and reattachment areas occur due to the backward-facing step flow. Control of these areas is very important to increase the amount of heat and mass transfer. In this study, in order to examine the effect of flow separation and reattachment, the heat transfer and flow characteristics of step corner structures with different chamfer lengths as h/4 and h/2 according to without chamfer (normal) geometry have been numerically researched in the vertically positioned backward-facing step flow geometry. One of the walls behind the backward-facing step has been kept at a constant temperature while the others are adiabatic. The results of the study have been obtained by solving conservation equations with three dimensional and steady k-ε turbulence model with Boussinesq approach using ANSYS-FLUENT computer program. Water and liquid sodium have been used as working fluids. Expansion rate of the backward-facing step is 1.5. The work has been performed at different Reynolds numbers as 5000 and 10000. The present study has been compared with the numerical results of the work found in the literature and it has been found that they are compatible and acceptable with each other. The results have been presented as the variations of Nu number, fluid temperature, turbulence kinetic energy and pressure. In addition, temperature, velocity and streamline distributions have been visualized in backward-facing step flow geometry. For Re=5000, the average Nu number value of the step geometry without chamfer (normal) in the liquid sodium flow has been determined to be 9% higher than the backward-facing step geometry with h/2 chamfer length.