Effect of particle size distribution on heat transfer in bubbling fluidized beds applied in thermochemical energy storage

The aim of the present work is to characterize the effect of particle size changes from cycling of the ther-mochemical energy storage material CaO/Ca(OH)2 on fluidizability and wall-to-bed heat transfer coefficients in the fluidized bed. Materials replicated from previous storage cyclization experiments are experimentally investigated in an ambient fluidization test rig. Differential pressure measurement and a horizontally immersed heat transfer probe are used to characterize fluidizability and wall-to-bed heat transfer between immersed cylinder and bed material. Sauter mean diameters of the replicated particle size distributions range from 27 mu m to 282 mu m. Particle size distributions with Sauter mean diameters significantly smaller than approximately 50 mu m were found to be difficult to fluidize due to excessive channeling, resulting in low heat transfer coefficients. In this case, fluidization quality and heat transfer is enhanced for higher gas velocities. Fluidizable particle size distributions ranged from Sauter mean diameters of 48 mu m to 282 mu m. Measured heat transfer coefficients show little dependency on the particle size. Observed maximum heat transfer coefficients range from 344 W m-2 K-1 to 350 W m-2 K-1.

Automated summary

The aim of this study is to analyze the impact of particle size changes on fluidizability and wall-to-bed heat transfer coefficients in a fluidized bed for the thermochemical energy storage material CaO/Ca(OH)2. Experimental investigation was conducted on materials replicated from previous storage cyclization experiments using an ambient fluidization test rig. It was found that particle size distributions with Sauter mean diameters smaller than approximately 50 μm were difficult to fluidize due to excessive channeling, resulting in low heat transfer coefficients. However, fluidizable particle size distributions ranged from Sauter mean diameters of 48 μm to 282 μm, and heat transfer coefficients showed little dependency on the particle size. The observed maximum heat transfer coefficients ranged from 344 W m-2 K-1 to 350 W m-2 K-1.