Investigation of thermal storage improvement using RT 70 HC phase change material solidification in finned triplex tube heat exchangers

Abstract

The solidification process of liquids is considered one of the important processes in industrial activities; therefore, this research revolves around the solidification process of PCM material within an annular space with stuck fins on the internal surfaces. The study was conducted through a numerical simulation, employing a comprehensive approach to analyze heat transfer and phase change dynamics. The research was carried out under initial operational conditions, focusing on the impact of fin material and configuration on the solidification rate. The research aims to clarify the solidification process of PCM material as a function of time and under the change in the natural state of the fins. The tested materials are Carbon, Aluminum, Copper, and Steel, with their thermal conductivity and heat distribution properties being critically evaluated. Results demonstrate that fins significantly accelerate solidification, with Copper fins achieving 53.6 % faster phase change than the finless case at 1000 s, reducing the liquid fraction to 0.21 versus 0.41 without fins. The superior performance of Copper stems from its high thermal conductivity (385 W/m·K), enabling 22 % greater energy extraction compared to the baseline. Steel fins, with lower conductivity (50 W/m·K), showed limited effectiveness, highlighting the direct correlation between material properties and solidification rates. In addition, Steel fins have less influence on the solidification speed compared to other materials, primarily due to their lower thermal conductivity.