Influence of hydrodynamic interactions among multiple bubbles on convective heat transfer in nucleate boiling

Takeyama, Mao (author), Zupančič, Matevž (author), Kunugi, Tomoaki (author)

To clear the effects of the hydrodynamic interactions among neighboring vapor bubbles on the saturated pool boiling heat transfer, artificial nucleation sites with several cavity arrangements were manufactured on the substrate surface and measured liquid temperatures near heated substrate by a miniature thermocouple probe with 10 kHz. The surface temperature of heated substrate was measured by an infrared camera with 1 kHz and bubble dynamics were simultaneously visualized by a high-speed video camera with 5 kHz and 10 kHz, respectively. The liquid temperature fluctuations, measured with micro thermocouple 100 %m and 10 %m above the substrate surface, were compared among each other and with the transient temperature fields obtained through IR measurements. Results showed that the hydrodynamic interaction among neighboring bubbles causes the liquid convection, that was only detected 100 %m above the boiling surface. Generally, the degree of liquid temperature fluctuations at 10 %m height and different arrangements of nucleation sites was under 1 K. Here the superheated sublayer in the vicinity of the boiling surface was generally not affected by the convection. Only when the coalescence from two neighboring nucleation sites occurred and the liquid-vapor interface nearly reached the substrate, a steep temperature drop over 2 K was detected. It was concluded that the viscous sublayer stably exists during boiling of water in lower heat flux conditions. To enhance the convective heat transfer in nucleate boiling, coalesced bubble needs to peel off the viscous sublayer during its deformation. Based on the measurements in this study, this peel-off effect only happens when the coalescence point is less than 1 mm above the heated surface.

• Language: English
• Keywords: nucleate boiling, bubble coalescence, superheated sublayer, convection effect, liquid temperature measurement, substrate temperature measurement
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Year: 2021
• Number of pages: Str. 1-11
• Numbering: Vol. 128, art. 110449
• PID: 20.500.12556/RUL-127505
• UDC: 536.24
• ISSN on article: 0894-1777
• DOI: 10.1016/j.expthermflusci.2021.110449
• COBISS.SI-ID: 66639875
• Publication date in RUL: 11.06.2021

Record is a part of a journal

• Title: Experimental thermal and fluid science
• Shortened title: Exp. therm. fluid sci.
• Publisher: Elsevier
• ISSN: 0894-1777
• COBISS.SI-ID: 170523

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
• Licensing start date: 01.10.2021

Secondary language

• Language: Slovenian
• Keywords: mehurčkasto vrenje, koalescence mehurčkov, pregreta plast, konvektivni učinki, meritve temperature v kapljevini, meritve temperature na površini