Performance Improvement of Parabolic Trough Collector With Thermal Oil-Based Metal-Oxide Nanofluids

Abstract

In this study, the effects of using thermal oil-based nanofluids on the parabolic trough collector (PTC) thermal performance are examined. A methodology is developed to predict the thermophysical properties of several combinations of thermal oils and nanoparticles. Specifically, Syltherm 800 and Therminol VP-1 are selected as they are common heat transfer fluids (HTF) to be combined with Al₂O₃ and CuO nanoparticles. The nanoparticle dispersion volume fractions (φ) are varied from 0.0% to 3.0% with increments of 0.25%. Additionally, it has been performed a parametric case study for a PTC plant, located in Rome to further emphasize the potential effects of using nanofluids in bulk-scale CST systems. The addition of nanoparticles to thermal oils used as HTFs in PTC systems results in a non-linear increase in both dynamic viscosity and thermal conductivity, leading to increased pumping power requirements and a moderate increase in thermal performance. The capacity factor and annual thermal energy are improved within the margins of 1.5% and 4%, respectively; however, these gains were offset by a significant rise in electricity consumption, especially for Therminol VP-1 based nanofluids due to plateau in thermal conductivity and nonlinear rise in dynamic viscosity against increasing volume fraction of nanoparticles. Unlike Therminol VP-1, the addition of nanoparticles has led to enhance the thermophysical properties of Syltherm 800 in the operational temperature range which led to an increase the annual thermal energy and capacity factor experiencing nonlinear increases in both thermal conductivity and dynamic viscosity.