Parametric Analysis of a Double Pipe Energy Storage Unit for the Recovery of Moderate Temperature Industrial Waste Heat: Combined Effect of the HTF Mass Flow Rate and the Eccentricity

The purpose of the present study is to perform an experimental and numerical investigation to analyze the thermal behavior and performance of an eccentric double pipe latent heat storage system (LHS), designed for industrial waste heat recovery application with moderate temperature, approximately 180°C. The LHS employs an industrial thermal oil as the heat transfer fluid (HTF), which circulates through the inner tube. Meanwhile, a phase change material (PCM), with moderate temperature, fills the an - nular space, functioning as a thermal energy storage medium. An in- house experimental setup was created, and experimental investigations were carried out. Subsequently, numerical analysis was conducted using ANSYS Fluent software. Validation of the numerical model was performed using the obtained experimental data. Then, a parametric study was conducted to explore the influence of the HTF mass flow rate and the eccentricity of upward and downward shifting of the inner tube. The results indicate that downward eccentricities offer superior heat transfer performance and reduce melting time compared to upward ones. For a mass flow rate of 17 × 10 − 3 kg/s, increasing the downward eccentricity from 0 to 0.13, 0.26, and 0.4 leads to reductions in melting time of 14.5%, 30.77%, and 24.78%, respectively. Furthermore, an increase in the mass flow rate improves heat transfer and reduces melting time for all eccentricities. Finally, results reveal that the best thermal energy storage unit configuration is obtained for a higher mass flow rate and a downward eccentricity of 0.26.