Buoyancy-opposed volumetric solar receiver with beam-down optics irradiation

Abstract

This paper describes a volumetric solar receiver that is vertically integrated with beam-down optics for condensed light irradiation. The heat-transfer performance of a silicon carbide honeycomb receiver was investigated using a 30-kWth solar simulator and numerical simulation. The experiments achieved an air temperature of 840 K at the receiver outlet by varying the operational parameters. Numerical simulations were performed for a vertical honeycomb block with beam-down irradiation and a horizontal honeycomb block with tower-type irradiation to elucidate the effects of buoyancy. Three blocks with different sizes were simulated for a variety of operational parameters. When the block was oriented vertically, the flow and temperature fields remained nearly symmetric in and near the receiver. In contrast, when it was oriented horizontally, the flow and temperature became asymmetric, with the hot spot moving toward the receiver's side wall and the stream in the receiver being reversed. The vertical orientation's robustness to buoyancy effects prevented any reduction in the receiver efficiency or outlet temperature and suppressed the thermal leakage.