Energy storage, one of the major challenges within the context of the energy transition, can take a variety of forms. For heat storage, one of the solutions developed at IFPEN is based on a fixed particle bed. A fluid flows through the bed to store the heat in the particles or to recover it(1).
Due to the complexity of these storage systems (large number of particles and non-linearity of the regimes studied), the use of numerical calculation is essential for dimensioning purposes.
To this end, a large number of calculations were performed to assess the impact of the variability of the different parameters (material, particle size and form, fluid type) on the overall performance of the solution.
This work highlighted two fundamental results:
• heat transfers within the bed vary locally in quite a significant way (figure). Hence, conventional approaches based on average volume methods, need to be enhanced to take into account these local fluctuations;
• the definition of the fluid reference temperature, necessary for assessment of fluid-particle heat transfers, is far from simple, due to the existence of a temperature distribution in the bed. Nevertheless, simulations confirmed its relevance when considered “ad infinitum”, i.e. far from the location of the bed where the calculation is performed.
The prospects for this research are numerous: in particular, the development of heat transfer laws, taking into account the effects of local heterogeneities, would pave the way for significant advances in the dimensioning of industrial beds.
a - A dimensionless number describing the intensity of heat exchange.
(1) M. Bélot, T. Phan, F. Euzénat, J-L. Pierson, D. Teixeira G. Vinay, Q. Falcoz, A. Toutant, A. Wachs. Turbulence, Heat and Mass Transfer 9. Brésil, 2018.