External authors:

• Raimundo Claren ( Pontificia Universidad Catolica de Chile )
• Ignacio Calderon-Vasquez ( Pontificia Universidad Catolica de Chile )
• Jose Ortega ( Pontificia Universidad Catolica de Chile )

Abstract:

Radial packed-bed thermal energy storage systems are increasingly researched due to their compactness and suitability for operation over a wide temperature range. However, the hydraulic behavior of radial-flow packed beds, particularly the effects of temperature and flow direction on pressure drop, remains insufficiently characterized. This work presents an experimental study of a 21.33 kWhth radial packed-bed thermal energy storage (RadTES) system using copper slag as the storage material and air as the heat transfer fluid. Pressure drop measurements were conducted under steady-state conditions at three operating temperatures (up to 180 degrees C) and mass flow rates up to 86.6 g/s, for both outward and inward flow configurations, and the data were analyzed using a quadratic Darcy-Forchheimer formulation. The results were compared against an empty-tank baseline to assess the effect of the porous medium on the overall hydraulic behavior. The experimental results show a consistent quadratic dependence of pressure drop on mass flow rate across all configurations, with measured pressure drops ranging from 63.2 to 257.4 Pa, regression errors below experimental uncertainty, and coefficients of determination ranging from 0.96 to 0.99. The fitted coefficients indicate a predominantly inertial flow regime across the studied mass flow range, with limited identifiability of the viscous term for several configurations and a systematic temperature dependence linked to air density variations. Furthermore, the presence of the porous medium did not systematically increase pressure drop in contrast to an empty tank, highlighting its flow-rectifying role and supporting the applicability of the proposed framework for system design and numerical modeling.