Numerical analysis of a new design strategy for parabolic trough solar collectors for improved production and consumption of solar energy in the Belt and Road Initiative countries

Abstract

Parabolic trough solar collector (PTSC) is one of the most encountered, effective, and economical devices to directly absorb solar energy in many Belt and Road Initiative (BRI) countries facing rapid need of energy due to economical and societal development. However, thermal efficiency of PTSC's receiver is still comparatively low because of its relatively high thermal loss. In this paper, addition of copper (Cu) nanoparticles into Therminol®VP-1 as heat transfer fluid (HTF) and installation of simple non-porous fins inside a PTSC's receiver were investigated to study their effects on performance improvement. Computational fluid dynamics (CFD) was employed in this work, where radiative heat transfer through the evacuated space between the glass envelope and receiver tube was included for model comprehension. After confirmation of mesh independence and experimental validation, influence of the number of fins and amount of Cu nanoparticles was discussed in detail. It is shown that installation of internal non-porous fins enhances heat transfer coefficient remarkably, and up to 16.3% increase of Nusselt number (Nu) is further achieved as the number of regular fins increases from 3 to 5. On the other hand, adding Cu nanoparticles into the Therminol®VP-1 increases thermal efficiency slightly but decreases friction factor (f) by 10.8% when volume fraction of Cu nanoparticles (φCu) increases from 0 to 0.04. This definitely shows the merit of Cu-Therminol®VP-1 as a HTF.