Session: 06-03: CSP Receivers and Reactors II

Paper Number: 157075

157075 - Geometric Optimization of an External Enclosure to Enhance Receiver Thermal Performance 

Abstract: 

Light-trapping planar cavity receivers (LTPCR) utilizing solid particles as heat transfer fluid are a promising candidate for 3rd-generation concentrating solar power (CSP) systems. Achieving high thermal efficiencies is imperative for the techno-economic competitiveness of CSP systems. Initial evaluations of the LTPCR thermal performance reveal high radiation and convection losses. The temperature difference between the hot receiver surfaces and the ambient environment mainly drives these losses. Radiation losses are further impacted by the view factors between exchanging surfaces. Enclosing the receiver with passive surfaces such that the temperature differential experienced by the receiver is reduced can potentially improve radiative and convective losses, and lead to efficient and long-lasting receivers. Studies have been conducted on enclosures surrounding other types of solar receivers and have proved to improve their thermal performance. This study focuses on the design of such an external enclosure surrounding an LTPCR. Refractory materials are often used for the walls of such enclosures. The use of a refractory material ensures that radiation leaving the hot receiver surfaces is reradiated back to the receiver. The refractory walls also reach high temperatures, reducing the temperature differential and the consequent losses. RSLE-57 is a potential candidate for the external enclosure wall material, which has been used in the design of enclosures for other solar receivers. RSLE-57 has a low thermal expansion coefficient and a low thermal conductivity at high temperatures and reflects well in most of the visible and infrared (IR) spectrum. Ansys Fluent is utilized as a computational fluid dynamics (CFD) tool to simulate the heat transfer and fluid dynamics surrounding the receiver-enclosure configuration. Two key input conditions are required for the CFD model: the solar flux absorbed by the receiver and the heat transfer characteristics to the particles. The absorbed solar flux profiles for the receiver are generated using Monte-Carlo ray tracing. The reduced order model thermal simulations of the full LTPCR inform the heat transfer coefficients to solid particles and particle temperature profiles. Surface-to-surface (S2S) radiation model is used to simulate the radiation exchange between surfaces. First, a base comparison case is simulated with and without the external enclosure to estimate the order of magnitude of loss reductions. For this base case, arbitrary dimensions are used for the external enclosure. After confirming the enclosure's effectiveness in reducing losses, its geometric parameters are varied, and thermal performance is evaluated. The optimum enclosure geometry is then determined to maximize optical and thermal performance. Additionally, a sensitivity analysis is conducted to assess the impact of key geometric features on the enclosure's optical and thermal performance.

Presenting Author: Chathusha Punchi Wedikkara Purdue University

Presenting Author Biography: Chathusha Punchi Wedikkara is a third-year PhD student in Mechanical Engineering at Purdue University. Their research centers on computational modeling of next-generation solar receiver systems. They employ finite-volume numerical methods to simulate heat transfer and fluid dynamics, advancing renewable energy technologies through innovative thermal system analysis.