关键词: 梯度分布, 相变储能, 流动传热, 金属骨架, 有限元方法

Abstract:

In this research, the finite element method is used to optimize the gradient pore density of the metal skeleton by using three different pore densities; five metal skeletons with different directions and gradients are prepared, and the heat transfer characteristics of the gradient pore density arrangement in different directions under the heating of the side wall are studied. The results show that the longitudinal negative gradient pore density skeleton has the best heat transfer effect; on this basis, the gradient distribution is optimized and the best working condition is obtained when the three-stage gradient is adopted, i.e., the longitudinal negative gradient two-time working condition. The longitudinal negative gradient structure considers the influence of skeleton heat conduction and flow heat transfer, thereby enhancing the heat transfer effect of the melting dead zone at the square cavity corner and improving temperature uniformity. Compared with the uniform skeleton, the complete melting time of the longitudinal negative gradient two-skeleton is shortened by 8.2%, especially after the liquid phase rate reached 0.9; the melting rate is increased by 29% and 14% compared to the transverse-negative gradient and the uniform square cavity, respectively. In comparison to the transverse and positive gradients, the phase change heat storage rates under the longitudinal negative gradient conditions are increased by 17% and 11.6%. In this study, it is proposed that the preparation of composite phase change materials by multi-stage gradient pore density metal framework is helpful to strengthen the energy storage efficiency of composite phase change materials without increasing the skeleton volume and provide a theoretical basis for better energy utilization.

Key words: gradient distribution, phase change energy storage, flow heat transfer, metal skeleton, finite element method