Research progress on silica nanofluids for convective heat transfer enhancement

With the rapid development of semiconductor and electronics technologies, high-integration and high-performance microelectronic devices play more important roles in industrial fields, such as the aeronautics and astronautics, energy, medical, and automobile fields. To avoid thermal failure in high heat flux conditions, effective thermal management of microelectronic devices is critical. Conventional air and liquid cooling approaches suffer from not only high power consumption but also low heat dissipation efficiency, considerably limiting the stability and reliability of microelectronic devices. In recent years, researchers proposed many passive (such as nanofluids, surface roughness, and heating element structures) and active (such as the acoustic, electric, and magnetic fields) heat transfer enhancement approaches. Because of its low cost, flexible control, and diverse forms, the nanofluid approach has attracted considerable attention. To solve the low thermal conductivity issue of conventional working fluids (such as water, ethylene glycol, and mineral oil), researchers have developed a series of particulate forms, including but not limited to silica dioxide (SiO₂), aluminum oxide (Al₂O₃), titanium dioxide (TiO₂), carbon nanotube, copper (Cu), silver (Ag), silicon carbide (SiC), diamond, iron oxide (Fe₂O₃), zinc oxide (ZnO), magnesium oxide (MgO), and cupric oxide (CuO). Particularly, silica (SiO₂) nanofluids, with their good mechanical and chemical stability, abundant structures, and diverse preparation methods, make them interesting to researchers. To date, SiO₂ nanofluids exhibit outstanding intensification performance in the fields of conduction, convection, and radiation heat transfer. This study provided a systematic overview of the research progress on SiO₂ nanofluids for convective heat transfer applications. First, the physicochemical properties and preparation methods (i.e., one-step and two-step methods) of SiO₂ nanofluids were introduced. Further, the state of the art of SiO₂ nanofluids for single-phase convection and phase change convection applications was summarized, and the numerical simulation and experimental observation results of natural convection, forced convection, pool boiling, and flow boiling were tabulated and discussed in detail. Finally, the current remaining challenges and future research directions were highlighted in terms of the in-depth heat transfer enhancement principles, practical industrialization applications, systematic and accurate evaluation of heat transfer performance, preparation and characterization strategies, exploration of a high-diversity library of particulate structures, and optimization of heat exchanger apparatus. We believe that this review article can shed new insights into the rational design and preparation of advanced SiO₂ nanofluids and provide important guidelines to develop robust nanofluid-based liquid cooling heat sinks.