An LBM study of multichannel flow boiling for electronic thermal management coupling flow instability mitigation

The rising heat dissipation requirement on electronic devices urges a more efficient and energy-saving cooling strategy to keep the equipment operating within a safe temperature range. Multichannel flow boiling provides a straightforward solution to this challenge due to enormous latent energy of vapor preventing heat accumulation. However, pressure drop minimization and flow instability mitigation should also be considered for optimizing multichannel design. Hence, a Lattice Boltzmann Method (LBM) study on multichannel flow boiling process is conducted to provide design-based suggestions. The effects of surface wettability, channel number, input heat flux, and inlet velocity on the two-phase flow characteristics, heat transfer coefficient enhancement, dimensionless pressure drop, and flow instability are compared to examine the overall performance. Non-dimensional pressure drop is proposed for comparison through dividing the pressure drop under two-phase flow stage by the pressure drop under single-phase flow stage. Results show that hydrophilic coating prevents the film boiling transition at high input heat flux and reduces the maximum temperature for safer electronic operation. Designing a dense channel array can enhance the overall HTC but also significantly increase flow instability on the inlet, leading to shorter pumping operation life. A hybrid design of multichannel with downstream microgap region is proposed, and results indicate great mitigation ability with the increase of gap length and inlet velocity. These findings offer an invaluable blueprint for multichannel heat sink design and reveal the mechanisms of flow boiling enhancement.