Review of methods for improving the thermal performance of solar air collectors with flat plates

Abstract

The latest research on improving the thermal efficiency of flat solar air collectors is carried out on the modification of the absorber surface, the organization of multiple air flow, the use of porous absorbers, the transfer of air flow to the absorber surface by impact, the integration of the absorber surface with heat accumulating materials. The formation of a laminar viscous layer on the surface of the absorber leads to the deterioration of heat transfer to the air stream. The main factor for increasing the heat transfer in flat solar air collectors is to increase the heat transfer surface and the air residence time in the collector, which is achieved by using fins, barriers, turbulizers and baffles. When installing turbulizers of different shapes on the surface of the absorber, the thermal efficiency of the collector increases from 71.4% to 93%. When the absorber surface is integrated with heat-accumulating materials and ribs, the daily thermal efficiency of the collector increases to an average of 0.4-4%. This review article presents an analysis of the scientific research conducted in the last decade on improving the thermal efficiency of flat solar air collectors.