The Effect of Nanoscale Surface Modification on Boiling Heat Transfer and Critical Heat Flux

Recently, there were lots of researches about enormous CHF enhancement with the nanofluid in pool boiling and flow boiling. It is supposed the deposition of nanoparticles on the heated surface is one of main reasons. In a real application, nanofluid has a lot of problems to be used as the working fluid because of sedimentation and aggregation. The artificial surfaces on silicon and metal were developed to have the similar effect with nanoparticles deposited on the surface. The modified surface showed the enormous ability to increase CHF in pool boiling. Furthermore, under flow boiling, it had also good results to increase CHF. In these studies, we concluded that wetting ability of surface; e.g. wettability and liquid spreading ability (hydrophilic property of surface) was a key parameter to increase CHF under both pool and flow boiling. In addition, using wettability difference of surface; e.g. hydrophilic and hydrophobic, we conducted some tests of BHT (boiling heat transfer) enhancement using the oxide silicon which have micro-sized hydrophobic islands on hydrophilic surface. By using both of these techniques, we propose an optimized surface to increase both CHF and BHT. Also, the fuel surface of nuclear power plants is modified to have same effect and the results shows a good enhancement of CHF, too.