High-temperature thermal energy storage is recognized to be a key technology to ensure future sustainable energy generation. Packed bed thermal energy storage is a cost-competitive large-scale energy storage solution. The present work introduces the experimental investigation of an innovative 49.7 kWh(th) radial-flow type high-temperature packed bed thermal energy storage under dynamic mass flow rates. Various dynamic air flow rate profiles, representative of different potential applications, have been tested during the charging process to investigate their influence on the thermodynamic performance of the storage. The outlet thermal power during the discharge has been controlled by managing the air flow rate. Short operational cycles have also been performed. The results show that dynamic mass flow rates can lead to a thermal efficiency reduction between 0.5 % and 5 % with respect to static conditions. Controlling the air mass flow rate could be an efficient strategy to stabilize the thermal power output during the discharge while minimizing peaks in the pressure drop. This work testifies that specific dynamic boundary conditions should be included during the thermal storage design process since they could largely affect the unit thermodynamic performance and potential scale-up. If no specific dynamic profiles are available during the packed bed storage design stage, it is suggested to consider typical dynamic profiles of the air mass flow rate to guarantee limited efficiency reduction during operation.