A realistic numerical model of lengthy solar thermal receivers used in parabolic trough CSP plants

摘要

Realistic models of flow receivers used in parabolic trough collectors found in certain concentrated solar power plants are crucial to understand and optimize the plant-system's performance. Since these receivers are typically extremely lengthy, simulations require large meshed domains. Additionally, the effects of selective emission and absorption are at times difficult to replicate. A simple yet novel approach in modeling tubular selective surface flow receivers of varying length utilizing a short domain of fixed length in ANSYS~R Fluent is thus presented. 2D and 3D representations are considered, where the domain contains only the receiver tube and heat transfer fluid. The effects of radiation and natural convection are included via a custom-written User Defined Function (UDF). An iterative procedure is used to determine the receiver's glass temperature and overall heat loss coefficient. Upon convergence, the results at the outlet are imposed on the inlet, allowing long receivers to be simulated using relatively short domains. In this regard, a 0.78m long domain was used to simulate a 7.8m long receiver. This methodology also permits receivers of varying length to be simulated with the aid of a single mesh of fixed length. Furthermore, the results of the 3D model agree with an existing experimental study to a higher degree than other studies that have been reviewed, confirming the physics of the model. The procedures outlined in this study may therefore be used in developing accurate representations of actual PTC receivers, where selective surface behavior is of importance. Finally, the use of a short domain of fixed length would undoubtedly reduce the required meshing time.