Numerical study on heat transfer augmentation techniques in concrete based thermal storage module for solar-thermal applications

Abstract

• Thermal performance of sensible heat storage prototype is studied. • Heat transfer augmentation is investigated by varying the fin configuration. • The maximum reduction in charging time is 36.9%/. • Proposed optimized model increases the discharging rate by 75.6%. • Trapezoidal fin configuration is the best option with 50–75% cost reduction. In this study, the development and performance analysis of a concrete based thermal energy storage module with a capacity of 170 MJ operating in the temperature range of 523 K to 623 K is presented. To enhance the heat transfer rate in concrete based sensible heat thermal energy storage (SHTES) systems, the well-proven technique of fin incorporation is implemented. Longitudinal fins are attached on the outer side of the heat transfer fluid supply tube without compromising the thermal storage/discharge capacity of the storage module. Numerical simulations have been performed using COMSOL Multiphysics to study the thermal performance of the module by varying the design parameters such as the number of fins, fin dimension, and fin shape. The thermal performances of the models with fins, in terms of charging/discharging time and heat storage/retrieval rate, are compared with the model without fins for the same boundary condition. From the numerical study, it is observed that the maximum reduction in charging/discharging times of the storage module is 36.9%/48.1% and 36.9%/45.6% for rectangular and trapezoidal fin shaped models, respectively, in comparison with the model without fins. Whereas, the corresponding enhancement in heat storage/heat retrieval rate is 58.5%/92.7% and 58.5%/83.7% for rectangular and trapezoidal fin shaped models, respectively, in comparison with the model without fins. By adopting a trapezoidal shaped profile model, the fin material usage can be reduced by 50–75% without compromising on thermal performance. This numerical analysis would facilitate the design and development of efficient storage modules for solar thermal applications.