基于多物理场协同调控的扭转流换热器传热强化和流阻抑制机理研究

In the thermal system of process industry, such as chemical industry, petroleum industry, etc., the shell-and-tube heat exchangers are widely used with the high energy consumption rate. This project aims to solve two serious problems, one is the high flow resistance accompanied with the improving of heat transfer performance, another is defect of revealing heat transfer enhancement and flow resistance control mechanism of flow pattern only considering the single physical field, such as flow rate, characteristic temperature difference, etc.. A new heat transfer enhancement and flow resistance control method caused by multi-direction twisty flow in shell side is presented. By combining theoretical analysis with numerical simulation and experimental verification, the heat transfer enhancement behavior rule of twisty flow is studied, the heat transfer enhancement and flow resistance control mechanism is revealed in a new opinion of multi-physics fields synergy, including velocity field, velocity gradient field and temperature gradient filed, etc.. Besides, the effect of various flow pattern in shell side on heat transfer enhancement and flow resistance control ability is quantitatively defined. The more perfect theoretical basis is proposed for improving and innovating the design and optimization tactics of shell structure. Based on the twisty flow in shell side, the new high efficiency and energy saving heat exchanger with significant heat transfer enhancement and flow resistance control ability is studied, the scientific design and optimization method system of advanced heat exchanger is developed, new techniques and equipments are supplied for raising the energy-saving and emission-reduction level of process industry in China.

本项目针对化工、石油等过程工业热力系统中应用极为广泛的管壳式换热器能耗较高的现状，着重解决换热性能提升的同时伴随较大流体流动阻力，以及仅考虑单一物理场（如流速、特征温差等）难以深层揭示流动形态影响传热强化和流阻抑制的本质机理，这两个突出难题。提出以壳程流体多向扭转流动实现传热强化和流动减阻的新思路，采用理论分析、数值仿真和实验研究相结合的方式，研究流体扭转流动强化热量传递行为规律，以速度场、速度梯度场、温度梯度场等多物理场协同调控的新角度阐明扭转流动传热强化和流阻抑制机理，并量化界定管壳式换热器不同壳程流态对传热强化和流阻抑制的影响能力，为发展创新壳程结构设计和优化策略提供更为完善的理论依据；基于壳程流体多向扭转流动，研究开发具有显著传热强化和流阻抑制能力的新型高效节能换热器，形成先进换热器设计和优化的科学方法体系，为提高我国过程工业节能降耗减排水平提供新技术和新装备。

管壳式换热器在过程工业中应用广泛，改进和提高其传热性能是节能减排的重要途径。本项目针对常规管壳式换热器能耗高、流阻大的弊端，开发研究新型高效节能扭转流换热器及其传热强化和流阻抑制机理，主要在以下方面开展了研究工作。.1.提出了壳程流体“扭转流”的新概念，达到传热强化过程中抑制流体流动阻力增大的目的，实现了传热强化过程的优化控制。扭转流强化了复杂流道中不同区域流体间相互作用，具有显著的增强流体掺混、分散和消除死区等能力，从而发展和创新了壳程结构设计理念。基于多物理场协同调控行为与传热和流动特性之间的关联，阐明了扭转流动传热强化和流阻抑制机理。.2.研制开发了采用新型管束支撑和扰流结构的高效节能扭转流换热器。成功诱发壳程流体的多向扭转流动，破除了常规壳程介质流动方式导致的弊端，实现了强化传热效率和降低壳程压降之间的优化平衡。采用理论分析、数值模拟、实验验证相结合的方式，探寻了关键元件结构参数和操作参数对壳程流体流动和传热性能的影响规律，为其结构改进、性能优化提供了参考依据。.3.量化界定了壳程典型流态，建立速度分量比例与破坏边界层能力的对应关系。提出速度分量比例因子η作为衡量不同流态对传热强化和流阻抑制影响能力的量化指标，扩展了传热传质学研究内容，为形成具有普适性的、新一代高效节能换热器开发、设计和优化策略，提供了理论依据、判定方法和实践积累。.本项目在增进对能量传递现象的认识、揭示流动传热本质机理、发展基于壳程新流态的先进热交换技术等方面取得了重要的理论和实践成果。研制开发的扭转流换热器具有显著的强化传热、降低流阻性能，较斜向流换热器相比，在同等质量流量下，传热系数提高10%，压降降低20%，综合性能（Nu/f）可提高30-40%，是降低常规管壳式换热器能耗的有效新途径，为提高工业节能减排技术水平提供了新技术和新装备，具有较为明显的经济、社会和环境效益。