Thermal efficiency and entropy generation for a parabolic trough receiver at different concentration ratios

Abstract

The use of high concentration ratio parabolic trough systems is emerging as one of the ways to further reduce the cost of energy from these systems. This paper reports on the thermal efficiency of a parabolic trough system and entropy generation in the parabolic trough receiver at different concentration ratios. In this study, the geometric concentration ratios considered were in the range 88-113, while the collector rim angle was taken as 80o. A combined Monte Carlo ray tracing and computational fluid dynamics procedure was implemented to obtain the numerical solution of the thermal and thermodynamic performance of the system. Results show that the thermal efficiency reduces by about 4.5% as the concentration ratio increases from 88 to 113 at a given flow rate, while the entropy generation rate is shown to increase with increasing concentration ratio. Results further show that there is potential for improved performance with heat transfer enhancement using Cu-Therminol®VP-1 nanofluid as the heat transfer fluid in the receiver’s absorber tube. For a system with a concentration ratio of 113 using Cu-Therminol®VP-1 nanofluid as the heat transfer fluid, the thermal efficiency increases by about 12% as the nanoparticle volume fraction increases from 0 to 6%.