The separation and the reattachment of nanofluid flow through a sudden expansion in an annular passage have been studied. ANSYS FLUENT was deployed to simulate the effect of separation of nanofluid flow on the local and average convection heat transfer in an annular passage. The outer tube was made of aluminium with internal diameter of 83 mm and horizontal length of 600 mm, subjected to a constant wall heat flux. The investigation was performed with varying Reynolds number ranging from 5000 to 25000, heat flux from 719 W/m2 to 2098 W/m2, and the enhancement of step heights expanding from 0 mm (d/D=1) to 18.5 mm (d/D=1.8). The increase of flow velocity results in the sudden drop of the surface temperature in proximity to the pipe entrance, followed by gradual increment of surface temperature along the pipe. The minimum surface temperature could be obtained at flow reattachment point. The position of the minimum temperature point is independent on the inlet flow velocity. In general, the average Nusselt number increases with the increase of Reynolds number.
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机译：已经研究了通过环形通道中突然膨胀的纳米流体流的分离和重新附着。部署ANSYS FLUENT来模拟纳米流体流的分离对环形通道中局部和平均对流传热的影响。外管由铝制成，内径为83毫米，水平长度为600毫米，并受到恒定的壁热通量。在雷诺数从5000到25000不等，热通量从719 W / m2到2098 W / m2以及台阶高度从0毫米（d / D = 1）扩展到18.5毫米（d / D = 1.8）。流速的增加导致靠近管道入口的表面温度突然下降，然后沿管道的表面温度逐渐升高。最低表面温度可以在流量重新连接点获得。最低温度点的位置与入口流速无关。通常，平均努塞尔数随雷诺数的增加而增加。
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