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2008 1

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Characteristics of flow and heat transfer of shell-and-tube heat exchangers with overlapped helical baffles

Tingting DU, Wenjing DU

《工程管理前沿（英文）》 2019年第6卷第1期页码 70-77 doi: 10.1007/s42524-019-0005-8

摘要：

The characteristics of flow and heat transfer of shell-and-tube heat exchangers with overlapped helical baffles (STHXsHB) were illustrated through a theoretical analysis and numerical simulation. The ideal helical flow model was constructed to demonstrate parts of the flow characteristics of the STHXsHB, providing theoretical evidence of short-circuit and back flows in a triangular zone. The numerical simulation was adopted to describe the characteristics of helical, leakage, and bypass streams. In a fully developed section, the distribution of velocity and wall heat transfer coefficient has a similar trend, which presents the effect of leakage and bypass streams. The short-circuit flow accelerates the axial velocity of the flow through the triangular zone. Moreover, the back flow enhances the local heat transfer and causes the ascent of flow resistance. This study shows the detailed features of helical flow in STHXsHB, which can inspire a reasonable optimization on the shell-side structure.

关键词： heat exchanger overlapped helical baffle triangular zone helical flow

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Parametric analysis and design equation of ultimate capacity for unstiffened overlapped CHS K-joints

CHEN Yu, ZHAO Xianzhong, CHEN Yiyi

《结构与土木工程前沿（英文）》 2008年第2卷第2期页码 107-115 doi: 10.1007/s11709-008-0014-x

摘要： A finite element model simulating an experiment on unstiffened, overlapped circular hollow structure (CHS) K-joints was generated and validated by comparing the ultimate capacities, deformation processes and failure modes of the experimental results. Using this model, the stress distribution, propagation of plasticity and the failure modes of overlapped joints with through-brace-in-compression and welded hidden seams were analyzed. The effect of geometric parameters, with or without hidden welds, and the loading hierarchy reversal of braces on the ultimate capacity of the joints were also studied. The results of finite element parametric analysis indicate that the brace-to-chord thickness ratio has relatively large effects on the failure mechanism and ultimate capacity of overlapped joints. It was also found that the absence of hidden welds has less significance on the ultimate capacity of through-brace-in-compression joints than through-brace-in tension joints. Finally, based on the design equation of gap joints, a formula predicting the ultimate capacity of overlapped CHS K-joints was derived by applying multivariate regression analysis. Results from the proposed design equation are consistent with experimental results.

关键词： regression analysis consistent unstiffened plasticity overlapped