Visualized effect of alumina nanoparticles surface deposition on water flow boiling heat transfer

The critical heat flux (CHF) enhancements obtained using nanofluids during pool boiling are well known, and the resulting delay reaching the film-boiling regime due to nanoparticles deposition on the heater surface has been investigated [1]. In this study, water boiling on a nanoparticles-coated heater was conducted at flow velocities ranging from 0 to 4 m/s, and the boiling heat transfer performance was assessed. Based on previous wetting-zone results, the nucleate boiling phenomenon was visualized using a highspeed video camera. Different wetting zones on bare and nanoparticles coated heaters were observed, and these influenced the boiling heat transfer performance. Additionally, the nucleate boiling wetting-zone fraction on the heater surface was related to the surface wettability. A new concept for a flow boiling model was proposed based on the wetting-zone fraction and was found to be in good agreement with the experimental data. (C) 2011 Elsevier Inc. All rights reserved.X111316sciescopu