金字塔凹表面构成通道内超临界CO₂流动二次流特性研究

Characterization of Secondary Vortices in Supercritical CO₂ Flow in a Channel Formed by a Concave Surface of a Pyramid

摘要: 超临界二氧化碳因自身特殊的物性广泛应用于各种能源系统，在高效性、环保性、可持续性等方面均具有明显优势，与常规流体相比，其可以打破传统稳态流动的传热限制，使传热更加均匀和高效。而印刷电路板式换热器因较大的传热面积密度和易于模块化的特性常作为超临界二氧化碳布雷顿循环发电系统的典型回热器被使用，故对以超临界二氧化碳为工质的印刷电路板式换热器进行研究很有必要。于是本文通过一种冲压的手段在流道表面形成金字塔结构壁面来强化换热，即通过二次流强化传热技术有效提高各项性能指标。而通道中诱导的二次流又受限于金字塔单元结构参数的变化，故通过仿真的手段重点探讨了金字塔单元结构参数的不同排列组合对二次流的影响。此外，还简要分析了超临界二氧化碳物性与二次流的关系。

Abstract: Supercritical carbon dioxide is widely used in various energy systems due to its special physical properties, and has obvious advantages in terms of high efficiency, environmental protection, sustainability, etc. Compared with conventional fluids, it can break the heat transfer limitations of traditional steady state flow and make heat transfer more uniform and efficient. The printed circuit plate heat exchanger is often used as a typical return heat exchanger in supercritical carbon dioxide Brayton cycle power generation system due to its large heat transfer area density and easy modularization, so it is necessary to study the printed circuit plate heat exchanger with supercritical carbon dioxide as the work material. Thus, in this paper, the heat transfer is enhanced by forming a pyramid structure wall on the surface of the flow channel by means of stamping, i.e., the performance indexes are effectively improved by the secondary flow-enhanced heat transfer technology. The secondary flow induced in the channel is limited by the variation of the structural parameters of the pyramid unit, so the influence of different combinations of the structural parameters of the pyramid unit on the secondary flow is emphasized by means of simulation. In addition, the relationship between the physical properties of supercritical carbon dioxide and the secondary flow is also briefly analyzed.