Inferences on the effects of geometries and heat transfer fluids in multi-cavity solar receivers by using CFD

This paper discusses about the design and analysis of a novel multi-cavity tubular receiver developed for small- and medium-scale concentrated solar power applications from the existing basic baffle-plated volumetric receiver model which is used in large-scale applications. The design and analysis work has been completed to enhance the thermal performance of cavity receivers for the average solar power input of 12 kW with a dish concentrator of 15 m² aperture area. This was carried out by replacing the baffle plates from the conventional basic volumetric receiver with multi-cavity tubes, keeping the heat transfer area as constant. The tubular arrangement improves the flow and heat transfer characteristics through minimized pressure drop. The receiver models with aluminum, copper, and silicon carbide materials have been analyzed using commercially available CFD software ANSYS-FLUENT for different flow rates of air and water. The computational analysis reveals that the thermal performance of a modified multi-cavity tubular receiver model made up of SiC material is better than receiver model with aluminum and copper materials. The maximum energy efficiency of 21.11% and 75.81% are achieved by the heat transfer fluids air and water, respectively. The maximum efficiency is achieved at the flow rate of 1.35 l/min and 0.9 l/min for the heat transfer fluids air and water, respectively. The study concludes that the multi-cavity tubular configurations may be well suited for small-scale CSP applications than the volumetric receivers with foams, rods, honeycomb, and baffle-plated structures.