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目的:明确在封闭腔内放置旋转柱体时,柱体尺寸及转速对不同浓度下纳米流体的流动传热的影响。创新点:1.数值模拟中采用的碳化硅-乙二醇(Si C-EG)纳米流体的重要热物性参数均为实验测量值;2.考虑封闭腔内柱体的动态旋转对腔内纳米流体流动传热的影响。方法:基于对Si C-EG纳米流体导热系数与粘度的实验测量,采用数值模拟方法探究封闭腔内旋转柱体、纳米流体浓度以及瑞利数对SiC-EG纳米流体流动传热性能的影响。结论:1.在柱体的旋转方向与由自然对流引起的纳米流体流动方向相同的情况下,置于腔内的旋转柱体可以起到强化传热的效果。2.二者旋转方向相反时情况较为复杂,当柱体尺寸较小且柱体转速较低时削弱传热效果;当柱体尺寸较大且转速较高而引发的强制对流占主导地位时,将对腔内传热起到一定的强化效果。
Objective: To clarify the effect of cylinder size and rotational speed on the flow and heat transfer of nanofluid at different concentrations when a rotating cylinder is placed in an enclosed chamber. Innovative points: 1. The important thermophysical parameters of the silicon carbide-ethylene glycol (Si C-EG) nanofluids used in the numerical simulation are all experimental values; 2. Considering the dynamic rotation of the cylinder in the closed cavity, Effect of fluid flow and heat transfer. Methods: Based on the experimental measurements of the thermal conductivity and viscosity of Si C-EG nanofluids, numerical simulation was used to investigate the influence of rotating cylinders, concentration of nanofluids and Rayleigh number in the closed cavity on the flow and heat transfer properties of SiC-EG nanofluids. Conclusions: 1. The rotating cylinder placed in the cavity can enhance the heat transfer effect when the rotation direction of the cylinder is the same as the flow direction of the nanofluid caused by natural convection. When the two directions of rotation are opposite, the situation is more complicated. When the cylinder size is smaller and the cylinder speed is lower, the heat transfer effect is weakened. When the cylinder size is larger and the rotational speed is higher, the forced convection dominates, Heat transfer to the cavity will play a certain degree of enhancement.