Karbon Nanotüp Nanoakışkanının Geriye Dönük Adım Akışında Isı Transferi ve Akış Karakteristiğinin Araştırılması

Abstract

The backward-facing step flow is important in many devices, such as the internal and external flow of heat storage containers or the collectors of power conversion systems, and stands out as one of the important geometric models due to the complex structure of the flow. In this study, heat transfer and turbulent flow properties of step corner structures with different chamfer lengths as h/2 and 3h/4 according to smooth (without chamfer) geometry have been numerically investigated at vertically placed backward-facing step flow geometry. In the backward-facing step geometry, only one of the walls has been kept at a constant temperature, while the other walls are adiabatic. Distilled water and MWCNT-distilled water nanofluid with a concentration of 0.01% by volume have been used as working fluid. Step expansion rate is 1.5. The results of the study have been obtained by solving three-dimensional, steady conservation equations using k-ε turbulence model, ANSYS-FLUENT program which is finite volume method with Boussinesq approach. 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=10000, normal geometry the where MWCNT-distilled water nanofluid has been used in the downstream region of the step geometry has provided an average Nu number increase of approximately 8.9% according to 3h/4 step geometry.