Bubble Lift-Off Diameter in Forced Convective Boiling Flow

2010 ◽  
Author(s):  
In-Cheol Chu ◽  
Chul-Hwa Song
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Bubble Nucleation ◽  
Present Observation ◽  
Convective Boiling ◽  
Digital Video Camera ◽  
Nucleation Frequency ◽  
Boiling Flow ◽  
Lift Off ◽  
Basic Features

A series of experiments were carried out to investigate the bubble nucleation to lift-off phenomena for a subcooled boiling flow in a vertical annulus channel. A high speed digital video camera was used to capture the dynamics of the bubble nucleation to lift-off process. A total of 148 recordings were made, and the bubble lift-off diameter and the bubble nucleation frequency were evaluated for 118 recordings up to now. The basic features of the lift-off diameter and nucleation frequency were addressed based on the present observation. A database for the bubble lift-off diameter was built by gathering and summarizing the data of Prodanovic et al., Situ et al., and the present work. The prediction capability of Unal’s model, Situ et al.’s model, and Prodanovic et al.’s correlation was evaluated against the database. The best prediction results were obtained by modifying the wall superheat correlation in Unal’s model.

Bubble Lift-Off Size in Forced Convection Subcooled Boiling

2003 ◽  
Author(s):  
Rong Situ ◽  
Ye Mi ◽  
Xiaodong Sun ◽  
Mamoru Ishii ◽  
Michitrugu Mori
Keyword(s):  
Forced Convection ◽  
Constitutive Relation ◽  
High Speed ◽  
Annular Channel ◽  
Video Camera ◽  
Bubble Nucleation ◽  
Force Balance ◽  
Subcooled Boiling ◽  
Digital Video Camera ◽  
Lift Off

Forced convection subcooled boiling experiments were conducted in a BWR-scaled vertical upward annular channel. Water was used as the testing fluid, and the tests were performed at atmospheric pressure. A high-speed digital video camera was applied to capture the dynamics of the bubble nucleation process. Bubble lift-off diameters were obtained from the images for a total of 91 test conditions. A force balance analysis of a growing bubble was carried out. A constitutive relation for bubble lift-off size was obtained by correlating current water data and R113 data from literature. The proposed constitutive relation and experimental data agree well with each other.

Effect of Hydrated Salt Additives on Film Boiling Behavior at Vapor Film Collapse

2008 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Furuya
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Film Boiling ◽  
Vapor Film ◽  
Quenching Temperature ◽  
Steel Sphere ◽  
Digital Video Camera ◽  
Collapse Temperature ◽  
Test Film ◽  
Film Collapse

A high-temperature stainless-steel sphere was immersed into various salt solutions to test film boiling behavior at vapor film collapse. The film boiling behavior around the sphere was observed with a high-speed digital-video camera. Because salt additives enhanced condensation heat transfer, the observed vapor film was thinner. Surface temperature of the sphere was measured. Salt additives increased the quenching (vapor film collapse) temperature, because frequency of direct contact between sphere surface and coolant increased. Quenching temperature rises with increased salt concentration. The quenching temperature, however, approaches a constant value when the slat concentration is close to its saturation concentration. The quenching temperature is well correlated with ion molar concentration, which is a number density of ions, regardless of the type of hydrated salts.

Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects

2006 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Lower Surface ◽  
Video Camera ◽  
Temporal Variations ◽  
Liquid Viscosity ◽  
Viscous Effects ◽  
Droplet Dynamics ◽  
Digital Video Camera ◽  
The Impact

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.

In-Flow Oscillation of Circular Cylinders in Cross-Flow

2007 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Hiroshi Haruguchi ◽  
Hiroyuki Nakajima ◽  
Toyohiro Sawada ◽  
Kozo Sugiyama
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Vortex Motion ◽  
Cross Flow ◽  
Video Camera ◽  
Circular Cylinders ◽  
Flow Oscillation ◽  
Single Cylinder ◽  
Digital Video Camera ◽  
Flow Oscillations

The importance of the in-flow oscillation of a single cylinder in cross-flow has been highlighted since an accident in a FBR-type reactor. In-flow oscillations have also been observed in tube arrays. This report is an experimental study on this phenomenon using totally nine cylinders in a water tunnel. Six cases, one single cylinder, two & three cylinders in parallel & in tandem, and a nine cylinder bundle, are examined. Every cylinder can move only in in-flow direction. The motion of cylinders is measured by the strain gages and by a high-speed digital video camera. The results are compared with the visualized vortex motion.

A Study on Stream-Wise Oscillation of Cylinder Arrays: Effect of Pitch Ratio

2009 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Takafumi Yoshikawa ◽  
Taku Yoshimura ◽  
Hironobu Kondo
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Cross Flow ◽  
Video Camera ◽  
Strain Gages ◽  
Flow Oscillation ◽  
Digital Video Camera ◽  
Cylinder Arrays ◽  
Tube Arrays ◽  
Pitch Ratio

The importance of the in-flow oscillation of a single cylinder in cross-flow has been spotlighted since an accident in a FBR-type reactor. However, the in-flow oscillation can be observed in tube arrays of heat exchangers. Previous reports show some interesting phenomena on the oscillation of cylinder arrays, which have a same pitch between cylinders. This paper shows the effect of the pitch ratio of a cylinder array on the characteristics of those phenomena, especially in in-flow direction, where every cylinder can move only in this direction. The motion of cylinders is measured by attached strain gages and by a high-speed digital video camera.

Simulation and experimental study of binder droplet infiltration in 3DP technology

2018 ◽  
Vol 32 (23) ◽  
pp. 1850272 ◽  
Author(s):  
Yuanyuan Wang ◽  
Pengfei Jia ◽  
Weidong Yang ◽  
Kai Peng ◽  
Sixiang Zhang
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Spherical Model ◽  
Ct Scanning ◽  
Video Camera ◽  
Nucleus Size ◽  
Digital Video Camera ◽  
Optimization Of Process Parameters ◽  
Industrial Ct ◽  
Droplet Infiltration

The purpose of this paper is to lessen the deviation of printing and to predict the nucleus size of binder droplet infiltration in three-dimensional printing (3DP) technology. The industrial CT is used to scan powders and the parameters of materials are calculated. A spherical model, which is based on the data from industrial CT scanning, predicts the nucleus size. The radius of the sphere is equal to the average radius of the sand particles. The spreading radius of binder droplet on the material is obtained by using the experimental method, and then the nucleus size is calculated by the equations. In order to do research on the process of droplet infiltration more intuitively, we analyze the effects of contact angle, porosity and drop height on the infiltration by using the software Comsol in the simulation. To verify the results of the simulation, the processes of infiltration are recorded by the high-speed digital video camera, and the nucleus size is observed by electron microscope. The study is important to conduct the infiltration experiments and provides a theoretical basis for optimization of process parameters in practical application.

Vibration of the Vocal Folds Observed Using a High-speed Movie System with Consumer Digital Video Camera

2009 ◽  
Vol 102 (5) ◽  
pp. 379-384
Author(s):  
Ken-ichi Kaneko ◽  
Koichi Sakaguchi ◽  
Masato Inoue ◽  
Fujinobu Tanaka ◽  
Atsushi Takano ◽  
...  
Keyword(s):  
High Speed ◽  
Digital Video ◽  
Vocal Folds ◽  
Video Camera ◽  
Digital Video Camera

scholarly journals Comparison of measurement methods of the front velocity of small-scale debris flows

2015 ◽  
Vol 46 (4) ◽  
pp. 129 ◽  
Author(s):  
Francesco Bettella ◽  
Gian Battista Bischetti ◽  
Vincenzo D'Agostino ◽  
Simone Virginio Marai ◽  
Enrico Ferrari ◽  
...  
Keyword(s):  
Debris Flow ◽  
High Speed ◽  
Video Camera ◽  
Significant Loss ◽  
Front Velocity ◽  
Small Scale ◽  
Mean Flow ◽  
Digital Video Camera ◽  
Transport Zone ◽  
Kinematic Behaviour

Debris flow is a gravity-driven process, which is characterized by a travelling dense surge including large boulders, and it is followed by a more fluid tail. These characteristics make difficult the measurement of the mean flow velocity by means of common hydraulic techniques. Different methods can be used at real scale and small-scale to measure the front velocity but a dedicate comparison between available methods is still lacking. This research aims to compare the front velocity measurements in the transport zone of a miniature debris flow using three devices: i) a common digital video camera (29 frames per second); ii) a high speed thermo camera (60 fps); and iii) a laser photoelectric sensors system. The statistical analysis of data has highlighted no significant differences exist between front velocities obtained by means of the video camera and the thermo camera, whereas photocells data statistically differ from those achieved via the other systems. Some lack of data recorded by photocell was documented, while the thermo camera technique did not show significant loss of information being also helpful to detect the kinematic behaviour of single particles. Finally, the tests confirmed the influence of the solid volumetric concentration in the debris-flow mechanics, which promotes, <em>ceteris</em> <em>paribus</em>, the debris-flow slowing down.

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