Enhanced boiling heat transfer on nanowire-forested surfaces under subcooling conditions

• Published in: International journal of heat and mass transfer 2018-05, Vol.120, p.1020-1030
• Main Authors: Lee, Donghwi, Kim, Beom Seok, Moon, Hokyu, Lee, Namkyu, Shin, Sangwoo, Cho, Hyung Hee
• Format: Article
• Language: English
• Subjects: Boiling heat transfer; Convection; Critical heat flux; Heat flux; Heat transfer; Nanowire-forested surfaces; Nanowires; Nucleation; Stability analysis; Subcooling; Surface stability; Temperature; Thermal stability
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2017.12.100

•Boiling experiment is conducted on nanowire-forested (NF) surfaces under subcooling.•Boiling performance is evaluated using a resistance temperature detector (RTD) sensor.•NF surfaces improve critical heat flux (CHF) by 4.3 folds under 30 K subcooling.•Spatial/temporal temperature variations reduced to 1/5 on 30 K subcooled NF surfaces.•Enhanced boiling heat transfer is analyzed by bubble images on subcooled NF surfaces. In boiling heat transfer, the emerging issues are the improvement of both the critical heat flux (CHF) and the thermal stability. Nanowire-forested (NF) surfaces and subcooled environments are favorable for improving CHF as well as the thermal stability owing to their distinctive morphology and consequential convection expedition, respectively. In this study, the improvement of CHF and temperature uniformity/stability are evaluated on NF surfaces immersed in de-ionized water with subcooling from 0 to 30 K using a resistance temperature detector (RTD) sensor with five measuring points. NF surfaces catalyze dispersed, confined and fast bubble ebullitions under subcooling conditions, resulting in the delayed bubble coalescences. This lead to the enhancement of CHF accompanying stabilized spatial/temporal temperature variations. We demonstrate that NF surfaces applying 30 K subcooled condition not only significantly improve the thermal stability by reducing spatial/temporal temperature variations to less than 1/5 but also enhance CHF by 4.3 folds, compared to the plain surfaces under the saturated condition. These remarkable enhancements show that NF surfaces can be effective solutions to secure the thermal stability under vigorous boiling conditions.