Superwetting surfaces can increase heat transfer and efficiency in two-phase cooling devices (heat exchangers).
Heat exchangers use boiling to transfer heat away from a solid. However, boiling is limited by the critical heat flux (CHF), which occurs at the Leidenfrost point, where a vapor is generated between the droplet and solid surface. The vapor causes heat transfer via conduction, which leads to dry-out and slows down heat transfer. A superwetting surface reduces the effects of the Leidenfrost effect by preventing vapor formation and continuously rewetting the surface; therefore, improving overall heat transfer.
Surface roughness can be used to create a superwetting surface that can fundamentally alter droplet-surface interactions to continuously rewet the surface and prevent vapor film formation. Micro scale square posts are fabricated on silicon wafers with photolithography followed by a reactive ion etch. Silica particles with different diameters, 15-75nm, are spin-coated and sintered on the substrates already having micro scale square posts to create a hierarchical structure. The textured surfaces significantly enhance nucleate boiling and diminish the Leidenfrost limits, which increases heat transfer and reduces dryout.
- Increases critical heat flux
- Increases boiling efficiency