A study of nucleate bubble growth on microstructured surface through high speed and infrared visualization

2017 ◽  
Vol 95 ◽  
pp. 12-21 ◽  
Author(s):  
Seol Ha Kim ◽  
Gi Cheol Lee ◽  
Jun Young Kang ◽  
Hyun Sun Park ◽  
Moo Hwan Kim
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Microstructured Surface ◽  
Nucleate Bubble

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.

scholarly journals Thermodynamic effects during growth and collapse of a single cavitation bubble

2013 ◽  
Vol 736 ◽  
pp. 44-66 ◽  
Author(s):  
Matevž Dular ◽  
Olivier Coutier-Delgosha
Keyword(s):  
Bubble Growth ◽  
Cavitation Bubble ◽  
High Speed ◽  
Phase Changes ◽  
Bottom Wall ◽  
Infrared Light ◽  
Delay Model ◽  
Light Spectrum ◽  
Temperature Variations ◽  
Thermodynamic Effects

AbstractThe thermodynamic effects associated with the growth and collapse of a single cavitation bubble are investigated in the present paper by an experimental approach. The study focuses on the temperature variations in the liquid surrounding the bubble. Experiments are conducted in a cylinder partially filled with water at an ambient temperature and atmospheric pressure. The bubble growth results from the expansion of an initial air bubble, due to the pressure wave generated by a so-called ‘tube-arrest’ method. Several locations of the bubble, at different distances from the bottom wall of the cylinder, are considered. The bottom wall is made of sapphire, which is transparent to both the visible and infrared light spectra which enables temperature measurements by a high-speed thermovision camera at a wavelength of 3–$5~\unicode[.5,0][STIXGeneral,Times]{x03BC} \mathrm{m} $. Water is opaque to the infrared light spectrum, hence only temperatures in the boundary layer and on the liquid vapour interface could be determined. A temperature decrease of ${\sim }3$ K was recorded during the bubble growth while an increase up to 4 K was detected during the collapse. Experimental results are compared to the predictions of the ‘thermal delay’ model based on the assumption that the bubble growth and collapse are due to phase changes only. In this approach, the temperature variations are related to the latent heat exchanges during the vapourization and condensation processes. On the basis of these results, the respective effects of phase change and air dilatation/compression in the bubble dynamics are discussed.

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.

Formation Mechanism and Characteristics of a Liquid Microlayer in Microchannel Boiling System

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Yaohua Zhang ◽  
Yoshio Utaka ◽  
Yuki Kashiwabara
Keyword(s):  
Bubble Growth ◽  
Weber Number ◽  
Kinematic Viscosity ◽  
High Speed ◽  
Growth Process ◽  
Gap Size ◽  
High Speed Camera ◽  
Region I ◽  
Laser Extinction ◽  
Region Ii

Experiments were performed using the laser extinction method to measure the thickness of the liquid film formed by growing flattened bubbles in a microchannel for gap sizes of 0.5 mm, 0.3 mm, and 0.15 mm. Water, ethanol, and toluene were used as test fluids. A high-speed camera was also used to simultaneously measure the bubble growth process. It was confirmed that the gap size and bubble forefront velocity determined the initial microlayer thickness. The variation trend of the microlayer thickness relative to the velocity of the interface was divided into two regions: region I, where the velocity is small and the thickness increases linearly with increasing velocity, and region II, where the thickness is almost constant or decreased slightly with increasing velocity. Furthermore, a nondimensional correlation for investigating the effects of test materials and gap sizes on microlayer thickness is presented. An analysis of the results showed that the boundaries of the two regions correspond to a Weber number of approximately 110, and in the region where the Weber number was smaller than 110, the thickness of the microlayer was thinner for the liquid whose value of ρ0.62ν0.42σ−0.62 was relatively small. However, for the region where Weber number was larger than 110, the smaller the kinematic viscosity of the liquid, the thinner the microlayer became.

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.

Bubble Growth in Surfactant Solutions

2010 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Bubble Growth ◽  
High Speed ◽  
Surfactant Solution ◽  
Life Time ◽  
Channel Length ◽  
Gap Size ◽  
High Speed Video ◽  
Surfactant Solutions

The presence of surfactant additives in water was found to enhance significantly the boiling heat transfer. The objective of the present investigation was to compare the bubble growth in water to that of a surfactant solution with negligible environmental impact. The study was conducted to clarify the effect of the heat flux on the dynamics of bubble nucleation. The bubble growth under condition of pool boiling in water and surfactant solutions was studied using high speed video technique. The bubble generation was studied on a horizontal flat surface; where the natural roughness of the surface was used to produce the bubbles. At heat flux of q= 10 kW/m2 the life-time and the volume of bubble growth in surfactant solution did not differ significantly from those of water. The time behavior of the contact angle of bubble growing in surfactant solution is qualitatively similar to that of water. At a heat flux of q= 50 kW/m2, boiling in surfactant solution, when compared with that of pure water, was observed to be more vigorous. Surfactant promotes activation of nucleation sites; the bubbles appeared in a cluster mode; the life-time of each bubble in the cluster is shorter than that of a single water bubble. The detachment diameter of water bubble increases with increasing heat flux, whereas analysis of bubble growth in surfactant solution reveals the opposite effect: the detachment diameter of the bubble decreases with increasing heat flux. Natural convection boiling of water and surfactants at atmospheric pressure in narrow horizontal annular channels was studied experimentally in the range of Bond numbers Bo = 0.185–1.52. The flow pattern was visualized by high-speed video recording to identify the different regimes of boiling of water and surfactants. The channel length was 24mm and 36mm, the gap size was 0.45, 1.2, 2.2, and 3.7mm. The heat flux was in the range of 20–500 kW/m2, the concentration of surfactant solutions was varied from 10 to 600 ppm. For water boiling at Bond numbers Bo<1 the CHF in restricted space is lower than that in unconfined space. This effect increases with increasing the channel length. For water at Bond number Bo = 1.52, boiling can almost be considered as unconfined. Additive of surfactant led to enhancement of heat transfer compared to water boiling in the same gap size, however, this effect decreased with decreasing gap size. For the same gap size, CHF in surfactant solutions was significantly lower than that in water. Hysteresis was observed for boiling in degraded surfactant solutions.

Characteristics of Nucleation and Bubble Growth During Microscale Boiling

2005 ◽  
Author(s):  
Yong Tian ◽  
Jiang-Tao Liu ◽  
Xiao-Feng Peng
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ccd Camera ◽  
Initial Position ◽  
Length Scale ◽  
Formation Theory ◽  
Nucleus Formation ◽  
Microlayer Evaporation ◽  
Parallel Microchannels

In this paper, both nucleus formation and bubble growth during boiling in microchannels were investigated. A series of visualized experiments were conducted to observe the boiling nucleation and bubble dynamics restricted within parallel microchannels on a silicon wafer. The channels were rectangular and had selected length scale ranging from 50 to 100 microns. A high-speed CCD camera was employed together with a microscope to dynamically record the boiling images. The rates of bubble growth were measured in the channels. The phase change nucleus formation theory was used to determine the initial position of the bubble. The bubble growth rate was described by two ordinary differential equations deduced from the microlayer evaporation theory. The calculation and experimental results were reasonably coincided.

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