Study on backward-facing step flow and heat transfer characteristics of hybrid nanofluids

As high heat dissipation has increasingly become the primary factor restricting the capability of electronic elements, and the high temperature of the equipment operation will affect its reliability. In this study, a backward-facing step (BFS) model to explore the flow and heat transfer characteristics of water and 5% mass fraction of Cu/Ni-water hybrid nanofluids has established. This paper focused on the influence of the number of step layers and the step expansion ratio (ER) on the flow and heat transfer characteristics of hybrid nanofluids. The increase in the number of steps will increase the Nu of the downstream wall of the steps and bring the peak position of Nu forward. The heat exchange effect of the hybrid nanofluids is better than that of water. The increase in flow velocity has the greatest influence on Nu of the lower wall of the step, followed by the increase in the step expansion ratio and the increase in the number of steps.