Surface roughening and hemi-wicking: Synergistic impact on flow boiling

This study advances thermal management in flow boiling by investigating the synergy between nanoscale surface structures, hemi-wicking, and bubble dynamics during phase changes, with a particular focus on innovative surface morphology. Nanowires, known for enhancing heat transfer through surface roughening and interfacial wicking, play a crucial role. We highlight the importance of morphological roughening and its synergy with hemi-wicking in enhancing critical heat flux (CHF) in flow boiling. We demonstrate that surfaces functionalized with vertical silicon nanowires show a significant increase in CHF compared to smooth surfaces. This enhancement is attributed to improved liquid supply and prevention of bubble pinning, thus maximizing heat dissipation. However, the absence of hemi-wicking on nano-inspired surfaces unexpectedly leads to a substantial CHF reduction compared to smooth counterparts. By visualizing bubble dynamics under forced convection, we reveal the critical role of hemi-wicking in sustaining continuous liquid supply and postponing the onset of film boiling by ensuring an anti-pinning effect of bubbles. These findings offer valuable insights into interface functionalization and surface morphology design for efficient heat dissipation, emphasizing the often-overlooked role of hemi-wicking in preventing bubble pinning. This knowledge is pivotal for developing compact and highefficiency cooling technologies.