Pool boiling performance of TiO2 superhydrophilic and Teflon superhydrophobic surfaces on evenly deposited copper frustums

Abstract

The miniaturization of electronic devices with ever-increasing functionalities inevitably results in greater thermal load on the devices. Hence, pool boiling, which utilizes the powerful latent heat of vaporization, is introduced as an effective method to manage severe thermal loads on miniaturized electronics. Hydrophobic surfaces tend to augment sufficient nucleation sites via roughening or low surface energy, while hydrophilic surfaces are prone to ample liquid supply, thus facilitating rapid bubble release and preventing surface dry-out. Herein, we compared the heat removal performance of TiO2-coated superhydrophilic and Teflon-coated superhydrophobic surfaces fabricated by aerosol deposition and supersonic spraying, respectively. TiO2 and Teflon particles were deposited on evenly patterned frustums. The resolution of the frustum is categorized as no-frustum, coarse, medium, or fine. We found that the surface wettability had little effect on the critical heat flux (CHF) for the no-frustum and fine cases. However, the CHF and effective heat transfer coefficient (heff) of the superhydrophilic surface increased considerably in the medium case. For the superhydrophobic surface, the presence of frustum deteriorated the pool boiling performance. Frustum texturing enhanced the pool boiling performance by increasing the number of nucleation sites and pathways of fresh liquid supply for the bare and superhydrophilic surfaces, but not for the superhydrophobic surface.

Keywords

• Aerosol deposition
• Supersonic cold spraying
• Pool boiling
• Wettability
• TiO2
• Teflon