Dynamics of Vapor Bubble Growth and Detachment in a Channel Flow

2006 ◽  
Author(s):  
G. Duhar ◽  
C. Colin
Keyword(s):  
Channel Flow ◽  
Bubble Growth ◽  
High Speed ◽  
Dominant Role ◽  
Bubble Radius ◽  
Video Camera ◽  
Vapor Bubbles ◽  
Equivalent Radius ◽  
Multiple Bubbles ◽  
Hot Film

The aim of this study is to improve the knowledge of the dynamics of vapor bubbles growing on a wall in a shear flow. Vapor bubbles are created on a hot film probe flushed mounted in the lower wall of a horizontal channel. The film overheat temperature controlled by an anemometer is limited to 20°C to avoid the growth of multiple bubbles. The liquid flow in the channel measured by Particle Image Velocimetry is laminar or turbulent. Bubble growth and detachment in the channel flow are filmed with a high-speed video camera at 2000 frame/second. Image processing allows obtaining the temporal evolutions of the bubble kinematics characteristics: the equivalent radius and the position of the centre of gravity. These data are then used to calculate the bubble growth rate and the forces acting on the bubbles during their growth and after their detachment. After detachment, drag, buoyancy and added mass forces play a dominant role. From the investigation of the bubble trajectories after detachment, the drag coefficient can be determined. When the bubble is attached to the wall capillary forces are dominant. A predictive model for bubble radius at detachment is provided depending on the wall overheat.

Collective Effects on the Growth of Vapor Bubbles in a Superheated Liquid

1984 ◽  
Vol 106 (4) ◽  
pp. 486-490 ◽  
Author(s):  
G. L. Chahine ◽  
H. L. Liu
Keyword(s):  
Collective Behavior ◽  
Bubble Growth ◽  
Theoretical Study ◽  
Pressure Field ◽  
Bubble Radius ◽  
Significant Inhibition ◽  
Collective Effects ◽  
Superheated Liquid ◽  
Vapor Bubbles ◽  
Bubble Interaction

The problem of the growth of a spherical isolated bubble in a superheated liquid has been extensively studied. However, very little work has been done for the case of a cloud of bubbles. The collective behavior of the bubbles departs considerably from that of a single isolated bubble, due to the cumulative modification of the pressure field from all other bubbles. This paper presents a theoretical study on bubble interaction in a superheated liquid during the growth stage. The solution is sought in terms of matched asymptotic expansions in powers of ε, the ratio between rb0, a characteristic bubble radius and l0, the interbubble distance. Numerical results show a significant inhibition of the bubble growth rate due to the presence of interacting bubbles. In addition, the temperature at the bubble wall decreases at a slower rate. Consequently, the overall heat exchange during the bubble growth is reduced.

Study of Subcooled Film Boiling on a Horizontal Disc:1 Part 2—Experiments

2000 ◽  
Vol 123 (2) ◽  
pp. 285-293 ◽  
Author(s):  
D. Banerjee ◽  
V. K. Dhir
Keyword(s):  
Liquid Phase ◽  
Particle Tracking ◽  
Bubble Growth ◽  
High Speed ◽  
Particle Tracking Velocimetry ◽  
Digital Camera ◽  
Film Boiling ◽  
Convection Flow ◽  
Vapor Bubbles ◽  
Natural Convection Flow

Experiments were performed to study subcooled film boiling of performance liquid PF-5060 (made by 3-M Company) on a horizontal copper disc. The experiments were performed for two regimes of film boiling involving departing vapor bubbles (low subcooling) and nondeparting vapor bubbles (high subcooling). By employing high speed digital camera, data were obtained for temporal variation of bubble height, bubble shape and bubble growth rate over one cycle. Heat flux data were deduced from temperatures measured with thermocouples embedded in the solid. The results from the numerical model are compared with experimental data and are found to be in general agreement. Particle Tracking Velocimetry (PTV) experiments were performed for a configuration of non-departing vapor bubbles to study the flow field in the liquid phase. The PTV experiments point to the existence of natural convection flow in the liquid phase and is in qualitative agreement with the predictions available in the literature.

An Experimental Investigation on the Effects of Heat and Mass Flux on Vapor Bubble Growth Characteristics in a Microchannel

2009 ◽  
Author(s):  
Zachary Edel ◽  
Abhijit Mukherjee
Keyword(s):  
Flow Rate ◽  
Heat Exchangers ◽  
Bubble Growth ◽  
High Speed ◽  
Flow Boiling ◽  
Bubble Formation ◽  
Flow Characteristics ◽  
Vapor Bubbles ◽  
Constant Flow Rate ◽  
Temperature Liquid

Micro heat exchangers are emerging as one of the most effective cooling technologies for high power-density applications. The design of micro heat exchangers is complicated by the presence of alternating flow regimes, which give way to flow boiling instability. Bubble formation inside microchannels can be correlated directly to flow boiling instability and can regulate flow characteristics and wall heat transfer when the bubbles grow to reach the microchannel hydraulic diameter. In this study, the growth of vapor bubbles in a single microchannel was examined using an experimental setup capable of measuring coolant flow rate, inlet and outlet liquid temperatures, and channel wall surface temperature. Liquid flow rate and wall heat flux were systematically varied while a high-speed camera was used to capture images of vapor bubbles forming in the channel. These images were used to compare bubble growth rates for a constant flow rate. The results provide fundamental understanding of the bubble growth process.

Bubble Characteristics During Boiling in Microchannels

2005 ◽  
Author(s):  
Jiang-Tao Liu ◽  
Yong Tian ◽  
Xiao-Feng Peng
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Solid Wall ◽  
Ccd Camera ◽  
Vapor Bubbles ◽  
Experimental Conditions ◽  
Boiling Process ◽  
Parallel Microchannels ◽  
Bubble Characteristics

A series of visualized experiments were conducted to investigate the boiling nucleation and bubble dynamics restricted within parallel microchannels on a silicon chip. The cross-section of each channel was 100 μm (W) × 100 μm (H). A high-speed CCD camera (up to 8,000 fps) was employed together with a microscope to record the boiling process. Under the present experimental conditions, the incipience of boiling was captured. The rates of bubble growth were measured at various flow and heating conditions. The interaction between vapor bubbles, vapor-liquid interface, and solid wall, was analyzed.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

2014 ◽  
Vol 782 ◽  
pp. 3-7
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Kohta Kadoi ◽  
Peng Wen
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Solidification Cracking ◽  
In Situ Observation ◽  
High Speed Video Camera ◽  
Varestraint Test ◽  
Solidification Cracks ◽  
Observation Method ◽  
Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

Effect of Pressure on Bubble Growth Within Liquid Droplets at the Superheat Limit

1982 ◽  
Vol 104 (4) ◽  
pp. 750-757 ◽  
Author(s):  
C. T. Avedisian
Keyword(s):  
Vapor Bubble ◽  
Bubble Growth ◽  
High Speed ◽  
Ambient Pressure ◽  
Organic Liquid ◽  
Liquid Droplets ◽  
Growth Data ◽  
Two Phase ◽  
Photographic Evidence ◽  
Good Agreement

A study of high-pressure bubble growth within liquid droplets heated to their limits of superheat is reported. Droplets of an organic liquid (n-octane) were heated in an immiscible nonvolatile field liquid (glycerine) until they began to boil. High-speed cine photography was used for recording the qualitative aspects of boiling intensity and for obtaining some basic bubble growth data which have not been previously reported. The intensity of droplet boiling was found to be strongly dependent on ambient pressure. At atmospheric pressure the droplets boiled in a comparatively violent manner. At higher pressures photographic evidence revealed a two-phase droplet configuration consisting of an expanding vapor bubble beneath which was suspended a pool of the vaporizing liquid. A qualitative theory for growth of the two-phase droplet was based on assuming that heat for vaporizing the volatile liquid was transferred across a thin thermal boundary layer surrounding the vapor bubble. Measured droplet radii were found to be in relatively good agreement with predicted radii.

Study on Magnetic Barrel Machine Equipped with Three-Dimensional Arrangement of Magnets

2007 ◽  
Vol 329 ◽  
pp. 761-766 ◽  
Author(s):  
Y. Zhang ◽  
Masato Yoshioka ◽  
Shin-Ichiro Hira
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Three Dimensional ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
The Media ◽  
Set Up

At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.

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