Performance evaluation of adding Helical-screw Tape Inserts in Parabolic Solar Trough Collectors as a Source of Cleaner Energy Production

Abstract

Abstract Solar have become an essential source of energy because of an increase in energy demand due to population explosion and global warming. Parabolic Trough Collectors (PTCs) are widely used for desalination, refrigeration, space heating and cooling purposes. The efficiency of the collectors decreases at high temperatures due to thermal losses. Helical screw inserts have the capability to increase the efficiency of the absorber tube of the collector. In the current study, the thermal and hydraulic performance of helical-screw tape inserts in a circular tube is investigated using Computational Fluid Dynamics (CFD) study for the Reynolds number range of 4400–7000. A parametric study is also performed to evaluate the geometrical parameters of inserts i.e. inserts thickness, helix angle and inner diameter. An increase of 53% and 23% was found in Nusselt number and Performance Evaluation Criteria (PEC) as compared to the base case. The parametric study shows that with the increase of thickness and helix angle, Nusselt number and pressure drop increases while by increasing the inner diameter, an increasing and then decreasing trend of Nusselt number was observed. The optimum value of PEC was found for insert thickness of 1\xa0mm, helix angle of 90° and inner diameter of 3.5\xa0mm. The modified inserts, with holes or fins in the inserts result in an increase in pressure drop with a small increase in Nusselt number. The tapered-helix design is advantageous as it reduces pressure drop by 12% at the expense of a 5% decrease in Nusselt number. Increasing PEC will be an effective step towards clean environment for PTC.