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.
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Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Notes on contributors
Nikhil Kanojia
Nikhil Kanojia is a Research Scholar in the School of Advanced Engineering, UPES Dehradun India. He is post graduated from UTU Dehradun. His research interest includes Thermal Systems, Thermal energy storage systems, and CSP.
Ram Kunwer
Ram Kunwer is an Associate Professor in the School of Advanced Engineering at University of Petroleum and Energy Studies, Dehradun, India. He is post graduated from Indian Institute of Technology, Delhi. His research interest includes Solar Thermal, thermal energy storage systems, and CSP.
Anil Kumar
Dr. Anil Kumar completed his doctorate in Thermal Engineering from the Indian Institute of Technology, Roorkee, in 2013 and his M.Tech in Thermal Engineering from Uttar Pradesh Technical University, Lucknow, in 2009. He worked as a post-doctoral researcher in the School of Mechanical Engineering at Kyungpook National University, South Korea, from 2013 to 2015.