Microfluidic one-step and large-scale production of silica and titania nanofluids toward phase-change heat transfer intensification of power electronic devices

The nanoparticles with uniform size and excellent stability scattered in fluid (termed as nanofluid) hold the potential to extricate high-performance electronics from the heat crisis. However, the simple, general, and large-scale production of nanofluids with high quality still remains a challenge. Here, we present a delicate design of microfluidic apparatus with extremely high throughput for silica (SiO₂) and titania (TiO₂) nanofluids synthesis to enhance flow boiling heat transfer. The microfluidic apparatus was composed of a three-microreactor array, and the spiral microchannel in the microreactor can efficiently mix the reagents by the secondary vortex. With the apparatus, 1 L of nanofluids can be generated in 20 min, and the synthesized nanofluids had a narrow size distribution below 100 nm and outstanding long-term stability at room (25 °C) and high (75 °C) temperature. The established heat transfer platform tested the heat transfer performance of SiO₂/TiO₂ nanofluids that the enhancement increased with the flow rate and decreased with the nanofluid concentration. The SiO₂ nanofluid always performed better than the TiO₂ nanofluid in the same condition. Maximumly, the critical heat flux (CHF) and heat transfer coefficient (HTC) were improved by 77 % and 96 %, respectively, for SiO₂ nanofluid, and they were raised by 44 % and 56 %, respectively, for TiO₂ nanofluid. The underlying mechanism of the difference was analyzed from the deposition on the surface and the bubble's coalescence. These results not only shed light on the industrial manufacture of various high-performance nanofluids, but also promote the thermal management of high-power electronics.