Effects of fin arrangement on the PCM melting in a vertical ‎double-tube heat ‎exchanger considering intermittent ‎boundary conditions

Document Type : Research Article


1 Department of mechanical engineering, university of Zanjan, Zanjan, Iran

2 Assistance professor, Faculty of engineering, University of Zanjan, Zanjan, Iran


This paper presents a numerical analysis of the solid-liquid phase change within a vertical double-tube ‎heat exchanger containing a phase change material, considering intermittent boundary conditions with ‎application of enthalpy-porosity technique. To enhance the rate of heat transfer, copper fins are ‎integrated on the inner wall of the heat exchanger in both uniform and non-uniform arrangements. ‎While the uniform placement of fins at equal intervals accelerates the melting process, it leads to a ‎portion of the phase change material remaining solid at the bottom of the heat exchanger due to ‎weakened natural convection. Conversely, positioning a greater number of fins with a non-uniform ‎distribution at the bottom of the heat exchanger expedites the overall melting process. It is observed ‎that compared to a finless heat exchanger and under constant boundary temperature, the complete ‎melting time is reduced by 53%, 69%, and 75% for uniform fin distribution, and fin distribution with ‎geometric progression q=2 and q=3, respectively. Furthermore, the findings showed that natural ‎convection leads to a greater increase in liquid fraction during melting compared to the assumption of ‎pure conduction. Specifically, liquid fraction increases by about 40% with natural convection and ‎around 15% with pure conduction during the first melting period. While the decrease in liquid fraction ‎is almost equivalent for both conditions during freezing. ‎


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