Automated high-speed video analysis of the bubble dynamics in subcooled flow boiling

2004 ◽  
Vol 25 (2) ◽  
pp. 149-158 ◽  
Author(s):  
Reinhold Maurus ◽  
Volodymyr Ilchenko ◽  
Thomas Sattelmayer
Keyword(s):  
Video Analysis ◽  
High Speed ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Subcooled Flow Boiling ◽  
High Speed Video ◽  
Subcooled Flow

Subcooled Flow Boiling in a Minichannel

2009 ◽  
Author(s):  
Akira Oshima ◽  
Koichi Suzuki ◽  
Chungpyo Hong ◽  
Masataka Mochizuki
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Maximum Heat ◽  
High Speed Video ◽  
Subcooled Flow

It has been considered that the dry-out is easy to occur in boiling heat transfer for a small channel, a mini or microchannel because the channel was easily filled with coalescing vapor bubbles. In the present study, the experiments of subcooled flow boiling of water were performed under atmospheric condition for a horizontal rectangular channel of which size is 1mm in height and 1mm in width with a flat heating surface of 10mm in length and 1mm in width placed on the bottom of the channel. The heating surface is a top of copper heating block and heated by ceramics heaters. In the high heat flux region of nucleate boiling, about 70 ∼ 80 percent of heating surface was covered with a large coalescing bubble and the boiling reached critical heat flux (CHF) by a high speed video observation. In the beginning of transition boiling, coalescing bubbles were collapsed to many fine bubbles and microbubble emission boiling was observed at higher liquid subcooling than 30K. The maximum heat flux obtained was 8MW/m2 (800W/cm2) at liquid subcooling of higher than 40K and the liquid velocity of 0.5m/s. However, the surface temperature was extremely higher than that of centimeter scale channel. The high speed video photographs indicated that microbubble emission boiling occurs in the deep transition boiling region.

Observation and modelling of bubble dynamics in isolated bubble regime in subcooled flow boiling

2018 ◽  
Vol 335 ◽  
pp. 400-408 ◽  
Author(s):  
Tomio Okawa ◽  
Kazuhiro Kaiho ◽  
Shintaro Sakamoto ◽  
Koji Enoki
Keyword(s):  
Bubble Dynamics ◽  
Flow Boiling ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Bubble Regime

Subcooled Flow Boiling on Micro-Porous Structured Copper Surface in a Vertical Mini-Gap Channel

2019 ◽  
Author(s):  
Junye Li ◽  
Kan Zhou ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
Copper Surface ◽  
Heat Fluxes ◽  
High Speed Flow ◽  
Subcooled Flow Boiling ◽  
Mass Fluxes ◽  
Speed Flow ◽  
Subcooled Flow

Abstract An experimental investigation of subcooled flow boiling in a large width-to-height-ratio, one-sided heating rectangular mini-gap channel was conducted with deionized water as the working fluid. The super-hydrophobicity micro-porous structured copper surface was utilized in the experiments. High speed flow visualization was conducted to illustrate the effects of heat flux and mass rate on the heat transfer coefficient and flow pattern on the surfaces. The mass fluxes were in the range of 200–500 kg/m2s, the wall heat fluxes were spanned from 40–400 kW/m2. With increments of imposed heat flux, the slopes of boiling curves for superhydrophobic micro-porous copper surfaces increased rapidly, indicating the Onset of Nucleate Boiling. Heat transfer characteristics were discussed with variation of heat fluxes and mass fluxes, the trends of which were analyzed with the aid of high speed flow visualization.

Measurement of the Vapor Blanket Thickness by Image Processing Method

2017 ◽  
Author(s):  
Fangxin Hou ◽  
Huajian Chang ◽  
Yufeng Zhao ◽  
Ming Zhang ◽  
Peipei Chen ◽  
...  
Keyword(s):  
Image Processing ◽  
Vapor Bubble ◽  
High Speed ◽  
Flow Boiling ◽  
Heating Surface ◽  
Processing Method ◽  
Flow Channel ◽  
Subcooled Flow Boiling ◽  
Image Processing Method ◽  
Subcooled Flow

It is widely believed that the behavior of vapor bubble/blanket over heating surface plays a critical role in determining the critical heat flux (CHF) in the subcooled flow boiling. Various CHF models are based on phenomenon observations of vapor bubble/blanket in the flow channel and use vapor bubble/blanket physical parameters to determine CHF values. In this study, subcooled flow boiling tests were conducted on the experiment facility “Test of External Vessel Surface with Enhanced Cooling” (TESEC). A series of natural circulation subcooled flow boiling CHF experiments is performed in a 30 mm by 61 mm rectangular flow channel with a 200 mm long heated surface along the flow direction at various inclination angles of the test section. With the assistance of high speed video technology, the process of flow boiling in the experiments was recorded and analyzed. A novel image processing method based on a MATLAB code is used to analyze high speed images at 999 frames/second and is able to provide detailed statistical information of vapor behavior on the heating surface. By this process, the static and dynamic information of vapor blanket is obtained at the pre-CHF conditions at various inclination conditions of flow channels (30 to 90 degrees). In addition, the Fast Fourier Transform (FFT) algorithm is used to further analyze the dynamic behavior of the vapor blanket.

Bubble Behavior and Mean Diameter in Subcooled Flow Boiling

1996 ◽  
Vol 118 (1) ◽  
pp. 110-116 ◽  
Author(s):  
O. Zeitoun ◽  
M. Shoukri
Keyword(s):  
Heat Flux ◽  
Mass Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Bubble Diameter ◽  
Image Processing Technique ◽  
Bubble Behavior ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
The Mean

Bubble behavior and mean bubble diameter in subcooled upward flow boiling in a vertical annular channel were investigated under low pressure and mass flux conditions. A high-speed video system was used to visualize the subcooled flow boiling phenomenon. The high-speed photographic results indicated that, contrary to the common understanding, bubbles tend to detach from the heating surface upstream of the net vapor generation point. Digital image processing technique was used to measure the mean bubble diameter along the subcooled flow boiling region. Data on the axial area-averaged void fraction distributions were also obtained using a single-beam gamma densitometer. Effects of the liquid subcooling, applied heat flux, and mass flux on the mean bubble size were investigated. A correlation for the mean bubble diameter as a function of the local subcooling, heat flux, and mass flux was obtained.

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