缠绕管式换热器壳程强化传热性能影响因素分析

由于内部流场信息缺乏，结构参数对流体流动的影响规律不明确，致使缠绕管式换热器壳程强化传热机理不明晰，阻碍其设计准则的进一步规范化和通用。针对上述问题，对缠绕管式换热器壳程流体流动进行几何建模及数值模拟，并通过文献中实验数据进行验证，进而基于该模型对壳程流体流场特性进行详细分析，分析关键结构参数对其壳程传热与阻力性能的影响，并探讨其强化传热机理。结果表明：Realizable k-ε湍流模型可较为准确地描述壳程流体流动；在双对数坐标系内，壳程Nusselt数随Reynolds数的增大而增大，阻力系数f则呈线性降低的趋势；壳程Nusselt数随缠绕管直径d与平均缠绕直径D的增大而增大，随螺距S的增大而减小，阻力系数f则相反；缠绕管直径d对壳程流体传热与阻力性能的影响最大，平均缠绕直径D的影响最小；增大缠绕管直径d与平均缠绕直径D有利于破坏流体速度边界层，增强流体扰动，加快温升速度，强化壳程传热，而增大螺距S则使速度边界层变厚，减小流动阻力的同时降低温升速度，不利于壳程强化传热。

Study on effects of structural parameters on shell-side heat transfer enhancement in spiral wound heat exchangers

Due to the lack of internal flow field information, the influence of structural parameters on fluid flow is not clear, which makes the heat transfer mechanism of the shell-tube heat exchanger shell side unclear and hinders the further standardization and generalization of its design criteria. Aiming at the above problems, geometry modeling and corresponding numerical simulations were carried out for the shell side flow of spiral wound heat exchangers. The feasibility and accuracy of these modellings were verified by comparing with experimental data in the literature. Then the flow field and characteristics of shell side fluid were investigated in detail. The heat transfer enhancement mechanism was further discussed based on the analysis of the influences of key structural parameters on the heat transfer and resistance performance. The results show that the fluid flow on the shell side can be described more accurately by using Realizable k-ε turbulence model. The Nusselt number increases linearly with the increase of the Reynolds number in a log-log coordinate system, while the friction factor f decreases linearly. The Nusselt number increases as the results of increased winding tube diameter d and average winding diameter D, and decreased pitch S. But it was opposite for the friction factor f. The heat transfer and resistance performance of the shell side are mostly affected by the winding tube diameter d, and the average winding diameter D does the least. Increased winding tube diameter d and average winding diameter D will break the boundary layer of the fluid flow. Then the fluid disturbance increases and hence the temperature increases faster. It is beneficial to enhance heat transfer on shell side. While increased pitch S will make the fluid flow much more smoothly, which causes velocity boundary layer to thicken. Thus flow resistance and temperature rising rate are reduced, it is not good for enhancement of heat transfer on shell side.