Experimental performance analysis of a parabolic trough solar air collector with helical-screw tape insert: A comparative study

Abstract

Abstract Heat transfer improvement efforts in parabolic trough air collectors (PTAC) are long-sought and much anticipated by many researchers, however, alternative heat transfer improvement methods such as helical screw tape insert inside the receiver tube has yet to be experimentally investigated. Therefore, in this study, a dual-function PTAC for low-medium temperature applications was experimentally tested in an indoor environment to assess its thermal characteristics. To increase the heat transfer performance, a helical screw tape was inserted along the pathway of air flow inside the receiver tube. To observe the effect, the PTAC system was tested with a helical screw tape insert and smooth absorber tube and the results were compared. Moreover, energy, exergy and thermal–hydraulic analysis of the PTAC was performed. Results show that the helical screw tape inserted PTAC always yields a much better performance in terms of overall collector efficiency and exergy efficiency. Overall results prove that the temperature rise improvement across the PTAC was remarkable, improving the efficiency by 56%–71% so that the role of the helical screw tape insert is to ensure an improved heat exchange. The findings validate the potential and elucidate specific conclusions for the practice of such heat exchange improvement methods in parabolic trough air collectors.