Thermal performance improvement of a LS-2 parabolic trough solar collector using porous disks

This study presents a thorough numerical investigation of a LS-2 parabolic trough collector (PTC) to introduce a manufacturable structure with high performance. This is done by considering all influential parameters such as possible design shapes (full, upward half, and downward half), diameters, spacings, and PPI (pores per inch) of porous materials along with thermal and fluidic features of heat transfer fluid used inside the absorber pipe. It is found that the full-disk cases perform better than half-disk options. Moreover, the thermal efficiency of PTC improves by increasing PPI and the diameter of porous disks, as well as by reducing the space gaps between the disks. Studying the effects of volumetric flow rate and inlet flow temperature shows that the thermal efficiency diminishes by increasing inlet temperature and decreasing flow rate. In addition, the variations of Nusselt number and friction factor for all mentioned parameters are studied, and performance evaluation criteria are developed to assess the simultaneous effects of enhancing heat transfer against increasing the pumping power.