Experimental and numerical heat transfer analysis of a V-cavity absorber for linear parabolic trough solar collector

In the present study, a V-cavity absorber with rectangular fins that can be used in the linear parabolic trough collector (PTC) system was proposed and investigated both theoretically and experimentally. The optical performance of the absorber was studied by means of Monte-Carlo ray-tracing (MCRT) method. An energy balance model and a more detailed three-dimensional numerical model were developed to analyze the flow and heat transfer characteristics. Moreover, an experimental setup was built to validate the theoretical analysis. A reasonable agreement between the theoretical and experimental results was achieved, which proves the feasibility and reliability of the models. The results show that the sunlight could be reflected repeatedly by the triangle shape and nearly no sunlight escapes. The absorber with rectangular fins has a better heat transfer performance with higher outlet temperature of heat transfer fluid (HTF), lower temperature of heating surface and lower heat loss than those of absorber without fins. The effects of heat flux distribution, mass flow rate and direct normal irradiance on the heat transfer performance were further discussed. In addition, the variations of the heat transfer coefficient along z axial direction with different mass flow rates were also calculated based on the numerical results.