晃荡条件下超临界CO2基混合工质的紧凑式换热器流动传热机理及结构优化方法研究

针对超临界CO2基混合工质改善超临界CO2布雷顿循环性能和适用范围的应用前景，以及紧凑式换热器作为循环关键部件在舰船或其他浮动式平台上的实际应用特点，开展晃荡条件下超临界CO2基混合工质在紧凑式换热器微细通道内的流动传热机理及结构优化方法研究。实验研究不同晃荡方式、晃荡参数和气热参数对微细通道内超临界CO2基混合工质传热和阻力特性的影响规律，建立多耦合因素下混合工质流动传热的理论模型。发展考虑工质热物性剧烈变化和晃荡运动影响修正的数值方法，揭示晃荡引起的离心力、切向力、科氏力等惯性力耦合工质强变物性对超临界CO2基混合工质流动传热性能及其脉动特性的影响机理。发展耦合微细通道单元和紧凑式换热器整体的多目标优化方法，并开展结构优化设计。为发展适用于复杂海况条件下的超临界CO2基混合工质紧凑式换热器，推动超临界CO2基混合工质布雷顿循环在舰船和其他浮动式平台上的工程化应用提供理论基础和技术支撑。

Based on the application prospect of the adoption of supercritical CO2-based mixtures for improving the system performance and operation range of the supercritical CO2 Brayton cycles, and the practical application characteristics of compact heat exchangers as key component of supercritical CO2 Brayton cycles applied on ships or other floating platforms, this project conducts investigations on the flow and heat transfer mechanism of supercritical CO2-based mixtures in the mini-channel of compact heat exchanger and its structure optimization method under the sloshing conditions. The effects of the sloshing forms, sloshing parameters and aerothermal parameters on the flow and heat transfer characteristics of the supercritical CO2-based mixtures in the mini-channel are experimentally investigated, and the theoretical models of flow and heat transfer of supercritical CO2-based mixtures under many parameters coupling effect are established. In addition, numerical methods accounting for the thermophysical property variations of the supercritical CO2-based mixtures and the influence of sloshing motions are developed. Besides, the influence mechanisms of the inertia forces induced by sloshing motions, including centrifugal force, tangential force as well as Coriolis force, coupling the thermophysical property variations of the supercritical CO2-based mixtures on the flow and heat transfer characteristics as well as pulsation characteristics of supercritical CO2-based mixtures are revealed. Furthermore, the multi-objective optimization methods coupling the mini-channel and the compact heat exchanger are developed, and the multi-objective optimizations on the compact heat exchanger structure are conducted. The presented research can provide basic theory and technical support for developing supercritical CO2-based mixtures compact heat exchangers employed in the complex sea conditions, and promoting the engineering application of the supercritical CO2-based mixtures Brayton cycle on ships and other floating platforms.