Heat uniformity, thermo-exergetic and hydraulic performance of parabolic trough solar collectors using ZnO-nanofluids

Parabolic trough collectors (PTCs) are key concentrating solar technologies for high-temperature heat generation, but their efficiency is limited by the thermal performance of the heat transfer fluid (HTF) and significant thermal losses. The integration of nanofluids has emerged as an effective approach to improve collector performance by enhancing thermal transport properties of HTFs. This study investigates thermal, exergetic and hydraulic performance of a PTC employing ZnO/TherminolVP1 nanofluid as heat transfer medium, and aims to evaluate the PTC performance under different operating conditions of temperature and flow rates, besides the effect of nanoparticle volume fraction ( v o l % ) on heat-transfer capacity, exergetic efficiency, and pressure-drop characteristics. A numerical and thermodynamic analysis was conducted using Computational Fluid Dynamics where governing equations for energy, momentum, and exergy balance were solved to evaluate the PTC behavior. Pressure drop and circumferential temperature distribution were also evaluated. The increase of v o l % leads to significant enhancement of thermal and exergetic efficiencies especially at high temperatures, where maximal enhancement found about 4.73% and 2.55% for thermal and exergetic efficiencies at ( T i n = 600 K , 8 kg/s ) and ( T i n = 400 K , 8 kg/s ), respectively, for 5% v o l % , as compared to basefluid. m ̇ have minor effect on PTC efficiencies, maximal augmentation reported less than 2.5% as m ̇ increases from 1 to 12 kg/s . Pressure drop is mainly affected by temperature and v o l % , with maximal and minimal values of 1130 and 746 Pa/m were found at (5% v o l % , 300 K) and (basefluid, 600 K), respectively. The findings demonstrate that ZnO-nanofluids can improve the thermo-exergetic performance of PTC systems while maintaining acceptable hydraulic performance compromise, advancing solar thermal energy applications.