Flow and heat transfer performance of shell-and-tube heat exchangers with fold helical baffles

doi:10.11949/j.issn.0438-1157.20170641

Abstract

Abstract:

A kind of shell-and-tube heat exchangers with fold helical baffles was proposed to eliminate the triangular leakage zones between adjacent baffles and shell. The effect of helical angle and overlapped degree on flow and heat transfer for shell-and-tube heat exchanger with fold helical baffles was studied based on investigation. The experimental correlations of convection heat transfer coefficient and resistance coefficient in shell side were obtained. The results show that the shell-side total pressure drop, shell-side tube bundle pressure drop, shell-side heat transfer coefficient and comprehensive performance all increase with the decrease of helical angle and the increase of overlapped degree under same shell-side volume flow rate. The flow and heat transfer performance of shell-and-tube heat exchanger with helical baffles is the best when helical angle is 18° and overlapped degree is 50%. The helical angle and overlapped degree as correction factor are added into experimental correlations. It is found that the average relative error between experimental values and experimental correlation of Nusselt number is 1.13%, the average relative error is 6.84% between experimental values and experimental correlation of resistance coefficient, which illustrates the fitting is correct and reliable. The results have a degree of theoretical guidance for design of shell-and-tube heat exchangers with fold helical baffles.

Key words: shell-and-tube heat exchangers with fold helical baffles, flow, heat transfer, triangular leakage zones, experimental validation, experimental correlation

摘要：

针对现有平面螺旋折流板换热器的相邻折流板与壳体间存在的三角漏流区，提出了一种折面螺旋折流板换热器。基于实验研究分析了折面螺旋折流板换热器的螺旋角和搭接度对流动传热性能的影响，并拟合了壳程对流传热和阻力系数的实验关联式。结果表明，当壳程体积流量相同时，随着螺旋角的减小，折面螺旋折流板换热器的壳程总压降增加，壳程管束压降增加，壳程膜传热系数提升，综合性能增强；相同壳程体积流量下，随着搭接度的增加，壳程总压降也增加，壳程膜传热系数增加，综合性能提高。实验研究表明螺旋角18°、搭接度50%的折面螺旋折流板换热器流动传热性能最佳。将折面螺旋折流板换热器的螺旋角和搭接度作为修正因子拟合到了实验关联式中，对比发现实验值与Nu实验关联式计算值的平均相对误差为1.13%，与f实验关联式的平均相对误差为6.84%，说明了拟合的正确性和可靠性。研究结果为折面螺旋折流板换热器的设计提供了理论指导。

关键词: 折面螺旋折流板换热器, 流动, 传热, 三角漏流区, 实验验证, 实验关联式

CLC Number:

TK124

WANG Simin, XIAO Juan, WANG Jiarui, JIAN Guanping, WEN Jian. Flow and heat transfer performance of shell-and-tube heat exchangers with fold helical baffles[J]. CIESC Journal, 2017, 68(12): 4537-4544.

王斯民, 肖娟, 王家瑞, 简冠平, 文键. 折面螺旋折流板换热器的流动传热性能[J]. 化工学报, 2017, 68(12): 4537-4544.

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