Exploring the role of surface roughness in concrete-based thermal energy storage systems: A computational study
Mohammad Rahjoo, Esther Rojas, G Goracci, Jorge S. Dolado
Abstract
This study computationally investigates the effect of thermal energy storage (TES) material surface roughness on heat transfer fluid (HTF) flow dynamics and heat transfer capabilities. The motivation is to further understand systems where concrete as the TES material directly interfaces with air as the HTF, based on previous research suggesting potential benefits of avoiding differential thermal expansion issues associated with metallic tubes. A k-ε turbulence model in COMSOL Multiphysics examined air flow over concrete surfaces with five levels of roughness from 0 to 3 mm peak height. Increasing surface roughness enhances turbulence and significantly improves heat transfer and thermal storage performance, with 7 % higher charging efficiency and energy storage capacity and 55.6 % greater heat transfer rate from 0.3 to 3 mm roughness, despite a 138 % increase in pressure drop. Applying artificial surface modifications like indentations or fins could further optimize efficiency by amplifying heat transfer advantages of increased roughness while moderating pressure losses. This indicates a promising direction for future research on enhancing thermal energy storage through concrete surface optimization and substantiates the potential of concrete as an inexpensive, scalable, high performance TES material.