Heat transfer in packed bed thermal energy storage with low Prandtl number fluid

低普朗特数流体填充床蓄热传热

• 批准号: 526152734
• 负责人: Dr.-Ing. Klarissa Niedermeier
• 金额: --
• 依托单位: Institut für Thermische Energietechnik und Sicherheit (ITES)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/526152734?language=en
• 关键词: Heat; transfer; packed; bed; thermal

In this project proposal, scientific methods for efficiency improvement and cost reduction of a packed-bed heat storage system, as a key component of the Carnot Battery, are addressed. As preliminary work showed, a packed-bed heat storage with liquid metals as heat transport fluid is able to perform more energy efficient than with conventional fluids, especially at low porosities in the packed bed (i.e. high solid fraction). The concept combines a low-cost packed bed and an efficient heat transport to the storage medium by using a heat transport fluid with high heat conductivity and low viscosity (low-Prandtl-number fluid, typically liquid metal). Therefore, it allows a separation of functions: The heat storage medium, one the one hand, can be chosen and optimized according to its storage parameters, e.g. large specific heat capacity and density and low cost; the heat transport fluid, on the other hand, offers high heat transfer rates and is only used in low quantities. Liquid metals offer significantly larger heat transfer rates compared with conventional fluids due to their thermal conductivities being one to two orders of magnitude larger. Furthermore, the use of liquid metal as the heat transport fluid allows the heat storage to be used in a Carnot battery over a flexible temperature range (e.g. with liquid sodium in the temperature range from 100°C to >500°C) without phase change and with highly efficient heat transfer in other system components like heat exchangers too. This enables compact and cost-efficient heat storage and energy conversion sub-systems in a Carnot battery. However, there is a gap in the literature regarding heat transfer correlations of low-Prandtl number fluids in packed beds. This is why this proposal focusses on the adaptation of a heat transfer correlation for forced convection of low-Prandtl number fluids in packed-beds based upon high quality experimental data. For this purpose, a project-specific test section is designed, constructed and integrated into an existing liquid metal test rig. The found correlation for the heat transfer is then included in an existing 2D-1D multi-scale model to improve the heat transfer model parameter being in the focus of this project. As a result, the simulation of the temperature field and, based on that, the dynamic behavior during charge, standby and discharge conditions, which forms the basis for efficiency evaluation and targeted design of storage systems in terms of capacity, geometry, material etc., can be optimized and exchanged with the partners within the Priority Program. To support the inverse approach and foster exchange with the partners in Subject Area B, the 2D-1D multi-scale model will be used already early in the project for fast evaluation of concepts, parameters, specification of exchange data etc.

在本项目建议书中，提出了作为卡诺电池关键组成部分的填充床蓄热系统提高效率和降低成本的科学方法。如初步工作所示，用液态金属作为传热流体的填充床热存储能够比用常规流体执行更高的能量效率，特别是在填充床中的低孔隙率（即高固体分数）下。该概念通过使用具有高导热性和低粘度的热传输流体（低普朗特数流体，通常为液态金属）将低成本填充床和到存储介质的有效热传输相结合。因此，它允许功能分离：一方面，可以根据其存储参数选择和优化热存储介质，例如大的比热容和密度以及低成本;另一方面，热传输流体提供高传热速率并且仅以低数量使用。与传统流体相比，液态金属提供显著更大的传热速率，这是由于它们的热导率大一到两个数量级。此外，使用液态金属作为热传输流体允许在灵活的温度范围内（例如，在100°C至>500°C的温度范围内使用液态钠）在卡诺电池中使用热存储，而没有相变，并且在其他系统部件如热交换器中也具有高效的热传递。这使得卡诺电池中的热存储和能量转换子系统紧凑且具有成本效益。然而，有一个空白，在文献中的低普朗特数流体在填充床的传热相关性。这就是为什么这个建议的重点是适应的传热相关性的强制对流低普朗特数流体在填充床的基础上，高质量的实验数据。为此，我们设计、建造了一个项目专用的试验段，并将其集成到现有的液态金属试验台中。然后将发现的传热相关性包含在现有的2D-1D多尺度模型中，以改进该项目重点关注的传热模型参数。因此，温度场的模拟以及基于此的在充电、待机和放电条件下的动态行为形成了效率评估和存储系统在容量、几何形状、材料等方面的有针对性设计的基础，可以与优先计划中的合作伙伴进行优化和交换。为了支持逆向方法并促进与主题领域B中的合作伙伴的交流，2D-1D多尺度模型将在项目早期使用，以快速评估概念、参数、交换数据规范等。