As parabolic trough systems with high concentration ratios become feasible, convective heat transfer enhancement is expected to play a significant role in improving the thermal and thermodynamic performance of these systems. In this paper, the thermal performances of a high concentration ratio system using three different types of nanofluids were investigated. A system with a geometric concentration ratio of 113 and a rim angle of 80° was used in this study. The nanofluids considered were copper-Therminol®VP-1, silver-Therminol®VP-1 and Al2O3-Therminol®VP-1 nanofluid. For each nanofluid, the volume fraction of the nanoparticles in the base fluid was varied from 0–6%. The numerical solution was obtained using a finite volume based computational fluid dynamics tool. Temperature dependent properties were used for both the base fluid and the nanoparticles. An actual receiver heat flux boundary condition obtained using Monte Carlo ray tracing was coupled to the computational fluid dynamics code to model the thermal performance of the receiver. Results show that for each nanofluid used, the thermal performance of the receiver improves significantly. The thermal efficiency increases by about 12.5%, 13.9% and 7.2% for the copper-Therminol®VP-1, silver-Therminol®VP-1 and Al2O3-Therminol®VP-1 nanofluids, respectively as the volume fraction increases from 0 to 6%. The thermal efficiency improvement with silver-Therminol®VP-1 was the highest of the considered nanofluids owing to the relatively higher thermal conductivity of silver.

This content is only available via PDF.
You do not currently have access to this content.