Abstract: Enhanced microchannel flow boiling heat transfer using nanofluids is an effective method to improve the heat transfer performance of high-power electronic devices.However，conventional nanofluids face the challenges of complex fabrication processes，poor stability，and the inability to control nanoparticle size，which negatively affect the overall heat transfer efficiency.A simple microfluidic synthesis strategy is developed to prepare highly stable and size-controlled silica nanofluids in a continuous，efficient and high-throughput manner.A specially designed helical microchannel reactor enables continuous flow one-step synthesis of stable nanofluids with controllable particle sizes ranging from 30nm to 110nm simply by flow rate adjustment.The results of flow-boiling heat transfer experiments show that at higher flow rates（0.4m/s），the heat transfer performance of smaller-sized nanoparticles（≤55nm） is better than that of larger-sized nanoparticles（110nm），and the enhancement for critical heat flux（CHF） and heat transfer coefficient（HTC） reaches 90.9% and 68% respectively.The enhanced wettability of the boiling surface，efficient surface nucleation，and improved bubble dynamics provide theoretical explanations for the enhanced heat transfer performance.These findings provide not only a new method for controllable preparation of nanofluids，but also new ideas for efficient two-phase chip cooling of power devices in aerospace and power electronics.

Key words:  , thermal management；flow boiling heat transfer；nanofluid；microchannel；enhanced heat transfer