Heat transfer enhancement of helical tubes during pool boiling

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer Pub Date : 2023-09-01 DOI:10.1016/j.ijheatmasstransfer.2023.124269

Mu-An Tsai , Liang-Han Chien , Chien-Yeh Hsu

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Abstract

This research utilizes experimental measures to investigate the heat transfer mechanism of helical tubes during saturated pool boiling. Experiments were carried out using R-134a and R-513A as working fluids, with saturation temperatures of 4.4 °C and 15 °C and heat fluxes ranging from 5 to 50 kW/ $m^{2}$ . The helical tube surface was heated by hot water with ascending heat flux. The helical test tubes used in this study are annealed smooth copper tubes with an outer diameter of 6.35 mm, tube thickness of 0.7 mm, coil diameter of 58.85 mm, number of turns of 3.5, and tube pitches ranging from 7 to 21 mm. Experimental results show that the tube bundle effect also exists in helical tubes as the boiling heat transfer coefficient obtained from helical tubes is significantly higher than that of single straight tubes predicted by the Cooper correlation. Furthermore, the boiling heat transfer coefficients obtained are greatly influenced by the tube pitch and show a tendency to increase with the decrease in tube pitch. In addition, larger and faster-moving bubbles are observed near the upper part of the helical tube due to agitations generated from the bottom part.

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池沸腾过程中螺旋管的强化传热

本文采用实验方法研究了饱和池沸腾过程中螺旋管的换热机理。实验采用R-134a和R-513A作为工质，饱和温度分别为4.4℃和15℃，热流密度为5 ~ 50 kW/m2。螺旋管表面被热水加热，热流密度呈上升趋势。本研究使用的螺旋试管为退火光滑铜管，外径6.35 mm，管厚0.7 mm，线圈直径58.85 mm，匝数3.5，管节距7 ~ 21 mm。实验结果表明，螺旋管中也存在管束效应，螺旋管沸腾换热系数明显高于单根直管的沸腾换热系数。沸腾换热系数受管距的影响较大，随管距的减小而增大。此外，由于底部产生的搅拌，在螺旋管的上部附近观察到更大、更快的气泡。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

International Journal of Heat and Mass Transfer 工程技术-工程：机械

CiteScore

10.30

自引率

13.50%

发文量

1319

审稿时长

41 days

期刊介绍： International Journal of Heat and Mass Transfer is the vehicle for the exchange of basic ideas in heat and mass transfer between research workers and engineers throughout the world. It focuses on both analytical and experimental research, with an emphasis on contributions which increase the basic understanding of transfer processes and their application to engineering problems. Topics include: -New methods of measuring and/or correlating transport-property data -Energy engineering -Environmental applications of heat and/or mass transfer