基于多孔网结构的斜温层储热罐性能改进数值模拟

Numerical simulation on performance improvement of thermocline energy storage tank based on porous mesh structure

[目的]为提升斜温层储热罐的储热性能,围绕斜温层储热罐内部结构优化问题开展研究.[方法]采用计算流体动力学方法,对常规结构、内置隔板结构和内置多孔网结构进行数值模拟和性能分析,获取流量对斜温层厚度和无量纲?损的影响规律,并研究不同黏性阻力系数下内置多孔网储热罐斜温层厚度的变化规律.[结果]多孔网结构储热罐中80℃的高温热水体积相比其他两种结构增加了15.38%;储热罐流量越大,斜温层厚度越大,无量纲?损越大;多孔网黏性阻力系数越大,斜温层厚度越小;流量为2.60 L/min时,内置多孔网储热罐的斜温层厚度相对于常规结构和内置隔板结构分别减小了31.58%和23.53%;内置多孔网储热罐的无量纲?损最低.[结论]多孔网储热罐储热性能优于常规结构和内置隔板结构储热罐,在储热罐中布置多孔网可以改善储热效果.

[Objective] The thermocline storage tank is a key component of thermal storage system with high efficiency and low cost,which can be integrated into a heating network for heat-power decoupling.In this study,we focus on improving the performance of the thermocline storage tank by optimizing its internal structure.Computational fluid dynamics(CFD) simulations were conducted to analyze the performance of three structures:conventional,built-in obstacle,and built-in porous mesh.The impact of flow rate on thermocline thickness and dimensional exergy loss was explored,and the rule of thermocline thickness with built-in porous mesh under different viscous resistance coefficients was studied.[Methods] The built-in porous mesh structure was proposed to improve the thermal performance of thermocline storage tank and was compared with the conventional and built-in obstacle structure to verify its thermal performance superiority.Three types of heat storage tank structures were modeled in 3D by SolidWorks.CFD simulations were then conducted to gain insight into the details of the flow and temperature fields of the heat storage tank.Additionally,a detailed parameter sensitivity analysis of the structure and operating conditions of the thermal performance of the thermocline storage tank were provided.[Results] The influence of different structures on the temperature change during the heat storage process is analyzed.The results show that the volume of hot water at 80 ℃ in the heat storage tank with a built-in porous mesh structure increases by 15.38% compared to the other two structures.The CFD simulation results also show that a larger flow rate leads to a greater thickness of the thermocline and dimensional exergy loss.This is caused by the fact that a larger flow rate leads to stronger perturbations in temperature fields.The dimensional exergy loss significantly increases at the initial and end stages of the heat storage process due to the violent mixture of hot and cold water in the heat storage tanks.The dimensional exergy loss of the heat storage tank with built-in porous mesh is the lowest throughout the entire heat storage process.The performance of the built-in porous mesh structure is related to its viscous resistance coefficient,and the results show that a larger viscous resistance coefficient of the porous mesh leads to a smaller thermocline thickness.At a flow rate of 2.60 L/min,the thermocline thickness of the heat storage tank with a built-in porous mesh is 31.58% and 23.53% thinner than that of the conventional structure and the built-in obstacle structure,respectively.[Conclusion] The results of the above evaluation indexes indicate that the heat storage tank with a built-in porous mesh outperforms the conventional and built-in obstacle heat storage tanks in terms of heat storage performance.The built-in porous mesh heat storage tank has the maximum volume of hot water with the target temperature,the thinnest thermocline,and the lowest dimensional exergy loss.The results of this study confirm the significance of the built-in porous mesh in enhancing the performance of heat storage tanks.The research methods and conclusions presented in this paper are of great reference value for the design and optimization of heat storage systems.Finally,it is important to note that the installation position of the porous mesh structure in the heat storage tank and the length-diameter ratio of the built-in porous mesh heat storage tank may affect the tank's heat storage performance.Further research is required to investigate these two aspects.