The primary objective of this study is to enhance the melting performance of phase change materials (PCMs) within a three-tube spiral heat exchanger an‎d to assess its potential as an efficient an‎d reliable thermal energy storage (TES) system. Owing to their high capacity for storing an‎d releasing latent heat, PCMs can play a significant role in improving energy efficiency an‎d mitigating fluctuations in heat supply an‎d deman‎d across various engineering applications. To accurately eva‎luate system performance, a three-dimensional numerical model based on computational fluid dynamics (CFD) was developed using ANSYS Fluent. The simulations employed the finite volume method with transient heat transfer modeling, while the melting behavior of PCMs was analyzed through the enthalpy–porosity method. A validation procedure was conducted by comparing the numerical results with reliable experimental data from the literature, confirming satisfactory agreement. Subsequently, the influence of several design an‎d operational parameters on the melting process was investigated. These parameters included the spiral pitch of the heat exchanger, the positioning of PCMs within the middle tube, the inlet velocity an‎d temperature of the working fluid, an‎d the incorporation of alumina nanoparticles at different volume fractions. The findings revealed that positioning the PCMs according to the second configuration enhanced the melting process by 37.5%. Furthermore, increasing the inlet temperature of the working fluid from 75 °C to 85 °C reduced the complete melting time by approximately 40%. In contrast, variations in spiral pitch an‎d inlet fluid velocity had negligible impacts on melting enhancement. Finally, to accelerate the melting rate, alumina nanoparticles were added to the PCMs at volume fractions of 1%, 2%, an‎d 3%. The results indicated reductions in melting time of 9.2%, 11%, an‎d 12.3%, respectively. Overall, the outcomes of this research provide valuable insights for the design an‎d optimization of PCM-based thermal energy storage systems in multi-tube spiral heat exchangers

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رامين كوهي كمالي , محمدرضا سليم پور