Assessment of a Falling Solid Particle Receiver with Numerical Simulation

Kurzfassung

An advanced computational fluid dynamics (CFD) model was developed which allows detailed analysis of a direct absorption falling particle receiver with horizontal aperture (face down) for a solar tower plant. The CFD model includes all relevant effects: movement of the particle curtain and the air, solar radiation, thermal radiation transfer, mechanical and thermal interactions between the particles, the air and the walls and conduction through the walls. These are spatially resolved in three dimensions for the complete receiver including the surrounding air. The coupled equations for thermal radiation, conduction and convective heat transfer are solved iteratively. First results are compared with previous simulations with a simple Matlab model and the differences due to the improvements in the simulations are discussed. The receiver efficiency was determined to be 83% at the design point (400 MW solar input) using a single drop (no recirculation) to heat the particles from 300 °C to 800 °C. In contrast, by separating the circumferential particle curtain into 4 parts and recirculating the particles 3 times through all the sections in series the receiver efficiency increases to more than 92%. This is due to lower reflection losses from the higher particle mass flow and therefore higher opacity of the particle curtain. Wind effects have been studied for the cylindrical face down receiver for the 100% load case with only one recirculation. For 15 m/s horizontal wind speed the receiver efficiency reduces from 89% to 84%.