Numerical modeling and parametric optimization of a dual media tank thermal energy storage system for enhanced industrial heat processes

Abstract

ABSTRACT In this study, a 1-D numerical model is developed to investigate the Dual Media Tank (DMT) thermal energy storage (TES) system. A physical model of 29 kWTH DMT is designed to evaluate the effect of parameters such as inlet velocity, pebble diameter and void fraction on discharging efficiency, friction factor and thermocline thickness. In addition, a Response Surface Methodology (RSM) is also used to optimize the design and operating parameters for maximum discharging efficiency and minimum pressure drop. The analysis result indicates a 41% increase in discharging efficiency and a 53% drop in friction factor for Reynolds number ranging from 16–23. However, a sharp increase in thermocline thickness (0.25–0.75 m) is found for Reynolds numbers ranging from 16–18; thereafter, the growth of thermocline thickness is slower. This shows that thermal degradation is higher for low Reynolds numbers. In this analysis, the effect of pebble diameter is also studied, and the result shows a 22% drop in discharging efficiency for pebble diameter varying from 0.03–0.09 m. In addition, the pebble diameter also affects the discharging time, and the result indicates a maximum discharging time of 40 minutes for smaller pebble diameters. Accordingly, parametric optimization has also been done to optimize the mass flow rate and pebbles diameter for maximum efficiency and minimum friction factor. The optimization result shows that a mass flow rate of 0.10 kg/s and pebbles diameter of 0.07 m is the optimum value for both minimal pressure drop and maximum discharging efficiency.