Optimization of Heat Transfer in Solar-Powered Biodiesel Reactors Using Alumina Nanofluids: A Combined Experimental and Numerical Study

The challenge posed by waste cooking oil (WCO) accumulation in sewage systems necessitates innovative solutions. This study presents an investigation into enhancing biodiesel production from WCO by augmenting heat absorption using oil-alumina nanofluids in a plug flow reactor powered by photovoltaic (PV) solar cells. Nanofluids with varying alumina concentrations (0%, 0.1%, 0.5%, and 2%) were examined. The investigation comprised two phases: Initially, nanoparticles were visualized via transmission electron microscopy (TEM), followed by the determination of nanofluid physical properties, including thermal conductivity, density, viscosity, and heat capacity. Subsequently, these properties were integrated into a finite element method (FEM) numerical simulation of the solar reactor using COMSOL Multiphysics. The study further involved design of experiments, regression analysis, and optimization techniques to elucidate the relationship between absorbed heat (Qc), oil flow rate (q), and nanoparticle volume percent (fi). The results indicate that an oil flow rate (q) of 0.0000173 m(3)/s and a nanoparticle volume percent (fi) of 2% significantly enhance heat absorption by approximately 43%. This research not only addresses the accumulation of WCO in sewage systems but also proposes a novel method to reduce fouling by utilizing biodiesel production. The findings underscore the efficiency of oil-alumina nanofluids in a plug flow solar reactor and the impact of varying nanoparticle concentrations on heat absorption. The physical properties of the nanofluid and its performance in the solar reactor are meticulously documented. Furthermore, the study delineates optimal operational conditions, resulting in a substantial increase in heat absorption. These insights are instrumental in developing sustainable waste oil management strategies and leveraging renewable energy sources within sewage systems.