Numerical investigation of transient flow characteristics and heat transfer in a fluidized bed particle solar receiver

The heat absorption efficiency of particles in a solar receiver is significantly affected by internal flow characteristics. A detailed investigation of the transient behavior of bubbles is essential for optimizing receiver design and improving its control. The present work investigates the transient flow characteristics and heat transfer in a fluidized bed particle solar receiver through numerical simulations with a Eulerian-Eulerian framework. The results reveal that the gas volume fraction showed significant temporal fluctuations, with increased gas flow rates and higher axial positions promoting the formation of larger gas core structures. The transient distribution of bubble diameters was obtained and analyzed. As the axial position and inlet flow rate increased, the growth rate of the cumulative curve declined, leading to a reduced cumulative probability of smaller bubbles. The power spectral energy was predominantly concentrated in the 0–1 Hz frequency range. With higher inlet flow rates, the spectral energy peak shifted leftward, indicating an extended period of bubble diameter variation. Finally, wall-to-bed heat transfer was analyzed. Higher flow rates led to improved temperature distribution and wall-to-bed heat transfer coefficient, but beyond a critical threshold, further increases would hinder effective heat transfer.