On the role of structural disjoining pressure and contact line pinning in critical heat flux enhancement during boiling of nanofluids

Boiling of nanofluids is reported to exhibit conflicting heat transfer trends compared to base liquids. On one hand, a deterioration of heat transfer in nucleate boiling regime and on the other hand a spectacular enhancement of critical heat flux are reported [S. M. You et al., Appl. Phys. Lett. 83, 3374 (2003); D. Milanova and R. Kumar, ibid. 87, 233107 (2005)]. The analysis and interpretation of these trends have so far been focused on the effect of nanoparticles on surface roughness, nucleation site density, and the use of hydrodynamics model for critical heat flux. In this letter a basic experiment is performed to propose a different approach to understand the mechanism through which the presence of nanoparticles acts on heat transfer during boiling of nanofluids. Pure ethanol and ethanol with aluminum particles evaporating on a hot polytetrafluoroethylene surface are investigated. The results indicate that the nanoparticles promote the pinning of the contact line of the meniscus and sessile drops. Th...