Canadian Journal of Chemical Engineering, Vol.97, 1399-1406, 2019
Experimental study of nucleate pool boiling heat transfer of self-rewetting solution by surface functionalization with TiO2 nanostructure
A titanium plate with titanium dioxide nanotube was prepared with the anodic oxidation process. The heat transfer through this plate was studied with quantitative heptanol solution as self-rewetting solution. The microstructure of this nano-structure surface was characterized by SEM and the surface tension of the self-rewetting solution on it was measured by the static contact angle. The results indicated that the heat transfer coefficient (HTC) and the critical heat flux (CHF) were significantly improved with the increasing concentration of heptanol. In the 0.1 mass% heptanol solution, the best heat transfer enhancement effect was obtained. The HTC is 22.46 kW center dot m(-2) center dot K-1 and CHF is 536.64 kW center dot m(-2), which were increased by 121 and 62.9 % more than those in the distilled water. According to the experimental phenomenon and mechanism analysis, the surface of the nanotube has a more effective vaporization core, greater roughness, and better wettability. Combined with the special double surface tension gradient characteristic of the self-wetting solution, the hot and cold liquid forms a microcirculation and the synergistic superposition of the driving force strengthens. The system can produce tiny and fine bubbles under low superheat, detach quickly, transfer heat quickly, and perform secondary wetting in time to achieve synergistic enhanced boiling heat transfer.