Engineering Applications of Nanofluid-Based Heat Transfer Systems in Renewable Energy and Advanced Manufacturing: A Review

Abstract

Thermal management is a major engineering bottleneck limiting performance and lifespan in high-heat-flux applications, including solar collectors and high-speed precision manufacturing. Conventional heat transfer fluids possess inherently low thermal conductivities, constraining heat removal. Nanofluids—engineered colloidal suspensions of nanometer-sized particles (1–100 nm) in base fluids—offer significantly enhanced thermophysical properties and convective heat transfer capability. This paper presents a comprehensive review evaluating the engineering applications, thermophysical mechanisms, operational challenges, and practical implementations of nanofluid systems across renewable energy (solar thermal collectors, PV/T hybrid systems, geothermal heat exchangers) and advanced manufacturing (minimum quantity lubrication in machining, electrical discharge machining, micro-electronics cooling). Key properties including thermal conductivity, viscosity, density, and specific heat capacity are analyzed alongside micro-scale heat transport mechanisms (Brownian motion, thermophoresis, nanolayering, particle clustering). Furthermore, long-term stability, surfactant chemistry, viscosity-driven pumping power penalties, channel erosion, and environmental impacts are examined. Synthesis of experimental and numerical data shows that hybrid nanofluids (e.g., Al2O3- MWCNT/water) yield thermal conductivity enhancements exceeding 28.5% and boost solar system efficiency by up to 18.2% while reducing tool-chip temperature in machining by over 25%. Critical research gaps and future commercialization pathways are discussed.  KEYWORDS: Nanofluids, Thermal Conductivity, Renewable Energy, SolarCollectors, Minimum Quantity Lubrication (MQL), Advanced Manufacturing,Hybrid Nanofluids, Dynamic Viscosity.