Experimental and Numerical Studies of Air Curtains for Falling Particle Receivers

The use of an air curtain blowing across the aperture of a falling-particle receiver has been proposed to mitigate convective heat losses and to protect the flow of particles from external winds. This paper presents experimental and numerical studies that evaluate the impact of an air curtain on the performance of a falling particle receiver. Unheated experimental studies were performed to evaluate the impact of various factors (particle size, particle mass flow rate, particle release location, air-curtain flow rate, and external wind) on particle flow, stability, and loss through the aperture. Numerical simulations were performed to evaluate the impact of an air curtain on the thermal efficiency of a falling particle receiver at different operating temperatures. Results showed that the air curtain reduced particle loss when particles were released near the aperture in the presence of external wind, but the presence of the air curtain did not generally improve the flow characteristics and loss of the particles for other scenarios. Numerical results showed that the presence of an air curtain could reduce the convective heat losses, but only at higher temperatures (>600°C) when buoyant hot air leaving the aperture was significant.Copyright © 2014 by ASME