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In the present study, a triplex-tube, employing fin-enhanced phase change materials (PCMs), as a thermal energy storage (TES) system was studied numerically. The main flaw of the PCMs is their low thermal conductivity that restricts their effectiveness for energy storage applications. Metallic (copper) fins are added to the geometry of the system to improve their function by extending the heat transfer area. The effects of the presence, configuration, and dimensions of copper fins were investigated to understand the best design for minimizing the solidification time and achieving the best performance enhancement for the TES system selected for this study. The results revealed that the best performance belonged to fins with a mix configuration, with an attachment angle of 90° and the length and width of 28 mm and 1 mm, respectively. Using this configuration could reduce the required time for complete solidification by around 42% compared to the system without fins. Moreover, it was concluded that increasing the length of the fin could offer its positive effect for enhancing the performance of TES system up to an optimal point only while increasing the width showed a diverse influence. Furthermore, the angles between the tube surface and the fin direction were investigated and 90° was found to be the best choice for the TES case selected in this study. In addition, placement of the fins on the surface of internal or external tube or mix method did not show a significant effect while placing the fins on the external surface of the tube showed even a negative impact on the performance of the TES system compared with when no fins were applied.

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O 2 Al ‫ﺑـﻪ‬ ‫ﻣﯿﺰان‬ 80 ‫دي‬ ‫ﭘﺎﯾﻪ‬ ‫ﺳﯿﺎل‬ ‫از‬ ‫ﺑﯿﺸﺘﺮ‬ ‫درﺻﺪ‬ ‫ﺑﻪ‬ ‫ﮔﻼﯾﮑﻮل‬ ‫اﺗﯿﻠﻦ‬ ‫آﻣﺪ.‬ ‫دﺳﺖ‬ ‫واژه‬ ‫ﻫﺎ‬ ‫ي‬ ‫ﮐﻠ‬ ‫ﯿ‬ ‫ﺪ‬ ‫ي‬ : ‫ﻣﺪل‬ ‫ﻧﺎﻧﻮﺳﯿﺎل،‬ ‫ﻣﯿﮑﺮوﮐﺎﻧﺎل،‬ ‫ﺣﺮارﺗﯽ،‬ ‫ﻣﺒﺪل‬ ‫ﻓﺸﺎر،‬ ‫اﻓﺖ‬ ‫ﺣﺮارت،‬ ‫اﻧﺘﻘﺎل‬ ‫ﺳﺎزي‬ . Abstract: The purpose of this article is the numerical study of flow and heat transfer characteristics of Nanofluids inside a* : ‫اﻟﮑﺘﺮوﻧﯿﮑﯽ:‬ ‫ﭘﺴﺖ‬ ‫ﻣﮑﺎﺗﺒﺎت،‬ ‫ﻣﺴﺌﻮل‬ azari.ahmad@pgu.ac.ir 64 ‫روش‬ ‫ﺳﺎل‬ ‫ﻣﻬﻨﺪﺳﯽ،‬ ‫در‬ ‫ﻋﺪدي‬ ‫ﻫﺎي‬ 38 ‫ﺷﻤﺎرة‬ ، 1 ، ‫ﺗﺎﺑﺴﺘﺎن‬ 1398 cylindrical microchannel with rectangular, the problem and extract the required data, a 3-D simulation was performed for the microchannel using ANSYS FLUENT 15.0 software and the effect of the cross-sectional shape of the fluid flow and the type of nanoparticles on the thermal transfer and fluid flow parameters was studied. From the obtained results, it can be observed that the addition of nanoparticles to the base fluid increases the heat transfer and pressure drop. The results also show that rectangular channels have the best performance among the three geometries examined as its heat transfer coefficient was 19.26% higher than the triangular cross section which had the worst performance. triangular, and circular cross-sections. The size and shape of these sections have a significant impact on the thermal and hydraulic performance of the microchannel heat exchanger. The Nanofluids used in this work include water and De-Ethylene Glycol (DEG) as the base fluids and Al2O3, Cu, SiO2 and CuO as the nanoparticles. To solve

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