Foamlike 3D Graphene Coatings for Cooling Systems Involving Phase Change.

Boiling is an efficient heat-transfer mechanism because of the utilization of latent heat of vaporization and has the potential to be used for cooling high-power electronic devices. Surface enhancement is one of the widely used techniques for heat-transfer augmentation in boiling systems. Here, an experimental investigation was conducted on chemical vapor deposition-grown three-dimensional (3D) foamlike graphene-coated silicon surfaces to investigate the effect of pore structures on pool boiling heat transfer and corresponding heat-transfer enhancement mechanisms. 3D graphene-coated samples with four graphene thicknesses were utilized along with a plain surface to investigate boiling heat-transfer characteristics and enhancement mechanisms. A high-speed camera was used to provide a deeper understanding of the bubble dynamics upon departure of emerging bubbles and visualize vapor columns in different boiling regimes. On the basis of the obtained results, in addition to interfacial evaporation, mechanical resonance of the 3D structure had also a considerable effect on vapor column formation. The results indicated that there is an optimum thickness, which exhibits the best performance in terms of boiling heat transfer.