Numerical investigation of radial-flow packed bed thermal energy storage systems: effects of particle size, layer ratio and aspect ratio

Date

2025-8-26

Author

Gürbüz Dinçer, Gül Nihal Asena

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This thesis presents a numerical study focused on the thermal and hydraulic behavior of high-temperature thermal energy storage (TES) systems utilizing radial-flow packed-bed configurations. With increasing demand for sustainable and efficient energy systems, optimizing TES design has become essential, particularly for integration with Concentrated Solar Power (CSP) plants and industrial heat recovery processes. The study employs a two-dimensional axisymmetric model developed in COMSOL Multiphysics, using the Local Thermal Non-Equilibrium (LTNE) and Brinkman-Forchheimer models to accurately simulate porous media flow and heat transfer. The analysis investigates how critical design parameters, such as particle size, layer ratio, and aspect ratio affect key performance metrics, including outlet temperature, average bed temperature, and pressure drop. A custom porosity estimation tool was also implemented to ensure realistic and consistent inputs across different configurations. Both single-layer and two-layer designs were tested under varying geometric and material conditions. Verification against numerical results from a well-documented radial TES prototype demonstrated strong agreement, with relative errors within 8%–13%, confirming the reliability of the model. The results indicate that reducing the particle size from 16 mm to 2 mm increases the outlet temperature by 10–12 °C and the average packed-bed temperature by a similar margin, while the pressure drop rises from about 2 Pa to nearly 250 Pa in single-layer cases. In two-layer configurations, the pressure drop varied between 1 Pa and 80 Pa, depending on the distribution of layers. Under these conditions, the outlet temperature changed by approximately 10 °C, while the average packed-bed temperature differed by up to 15 °C. Aspect ratio variations also had a significant impact: increasing AR from 0.6 to 1.0 reduced the thermal response, with average bed temperatures decreasing by about 20–25 °C. These quantitative results highlight the sensitivity of radial packed-bed TES systems to geometric and particle-scale parameters, defining the balance between thermal performance and hydraulic resistance.

Subject Keywords

COMSOL Multiphysics, Numerical Simulation, Packed Bed, Radial Flow, Thermal Energy Storage

URI

https://hdl.handle.net/11511/116575

Collections

Graduate School of Natural and Applied Sciences, Thesis