Abstract:

Twisted tapes, as one of the core inserts for enhancing convective heat transfer within pipes, has attracted significant attention due to their simple configuration and ease of engineering implementation. However, the structural design of twisted tapes typically relies on a trial-error method, leading to a persistent deviation from the ideal longitudinal vortex field based on heat transfer optimization theory. This article reviewed the research progress of twisted tape structures and highlighted that the fine regulation of vortex structures was key to balancing the enhancement of heat transfer performance and flow resistance. It further discussed the hydrodynamic characteristics of heat exchangers that were enhanced by the compound techniques involving the combination of twisted tape with vortex generators or shaped tubes, granular flow and external field. It suggested that the deep coupling of vortex flow, oscillating flow, and secondary flow was critical for achieving fine control of the vortex field, which could effectively take into account the disturbance in heat transfer near the pipe wall and in the central region. Subsequently, in the context of typical industrial applications, such as the use of short-length twisted tape in the enhancement of hydrocarbon pyrolysis reaction processes, it was pointed out that under the extreme harsh conditions characterized by high heat flux, short residence time, and easy coking, the decaying vortex structure with rigid swirling flow and induced secondary longitudinal vortices was the ideal flow field for adapting to this special heat exchange system. Therefore, how to properly handle the competitive and synergistic relationship between the rigid swirling flow near the pipe wall and the secondary vortices in the central region has emerged as a new challenge that needs to be urgently resolved in the development of efficient, low-resistance, and reliable twisted tape-enhanced heat transfer technology.

Key words: twisted tape, heat transfer enhancement, swirling flow, secondary vortex, hydrocarbon pyrolysis

摘要：

扭带作为管内涡流强化传热的核心元件之一，因其构型简单、易于工程实施而受到重要关注。然而，扭带的结构设计普遍采用试差法，导致管内流动结构始终偏离基于传热优化理论的理想纵向涡流场。本文阐述了扭带结构的研究进展，并指出涡流结构的精细调控是平衡强化传热效果与流动阻力的关键。进一步讨论了基于扭带的构型复合、颗粒流复合和外场复合强化传热管内流体力学特性，认为涡旋流、振荡流和二次流行为的深度耦合是实现涡流场精细调控的切入点，这可以有效兼顾管壁附近流体和中心区域流体的扰动换热。随后，针对扭带在烃类热解反应过程强化这一典型工业应用，指出在该工艺的高热流密度、短停留时间、易结焦等极端恶劣的工况条件下，刚性旋流内置二次纵向涡旋的衰减涡流结构是适应该特殊换热体系的理想流场。因此，如何处理好管壁附近刚性旋流与中心区域二次涡旋之间的竞争-协同关系，成为了高效、低阻、可靠扭带强化传热技术发展过程中亟待解决的新问题。

关键词: 扭带, 强化传热, 涡流场, 二次涡旋, 烃类热解