Conjugate heat transfer modeling and asymmetric characteristic analysis of the heat collecting element for a parabolic trough collector

Abstract

We analyzed in this study the conjugate heat transfer process in the heat collecting element (HCE) for a parabolic trough concentrator. The effect of asymmetric characteristics, such as non-uniform heat flux, eccentric configuration, and incident angle, are especially considered in this paper. We constructed a two-dimensional model of surface radiative transfer coupled with convection using the finite volume method combined with the net radiation method. We presented a detailed numerical method in which we applied an additional source term method to the boundary conditions to capture the absorption and emission processes in the coating of the HCE. The results were validated against the experimental data. Thus, we were able to identify the limiting interactions between thermal radiation and convection in the annulus. We systematically analyzed the effect of the incident irradiation angle and the eccentricity of the configuration on heat loss through the annulus of the HCE under two limiting conditions: “air in annulus” and “vacuum in annulus”. The results show that asymmetric characteristics, especially the non-uniform heat flux and eccentricity configuration, have a significant influence on local heat transfer processes. These insights may be used to further optimize the configuration of the HCE for improved thermal performance.