Effects of Heating Surface Materials on a Liquid–Solid Contact State in a Sessile Drop-Boiling System

1993 ◽  
Vol 115 (1) ◽  
pp. 222-230 ◽  
Author(s):  
S. Inada ◽  
W.-J. Yang
Keyword(s):  
High Speed ◽  
Sessile Drop ◽  
Bubble Radius ◽  
Heating Surface ◽  
Experimental Investigations ◽  
High Speed Photography ◽  
Solid Contact ◽  
Contact State ◽  
Interfacial Pressure ◽  
The Relationship

Three experimental investigations are performed on the liquid–solid contact state at the instant when a liquid comes in contact with a heating surface in the transition-boiling regime between the maximum evaporation rate point and the spheroidal state: (1) measuring the piezoelectric potential by means of a quartz oscillator being placed on the heating surface, (2) monitoring the boiling sound generated at the instant of liquid–solid contact using a condenser microphone, and (3) observation of drop behavior, by means of high-speed photography. The information obtained from these three investigations is synthesized to quantify the liquid–solid contact state. The study has disclosed the roles of thermal properties and heating surface temperatures on the endurance time of the instantaneous liquid–solid contact state and the relationship between the critical bubble radius and the measured vapor–liquid interfacial pressure difference.

Analysis of Droplet Impacting on Inclined Wall

2020 ◽  
Author(s):  
Bowen Chen ◽  
Bo Wang ◽  
Bingzheng Ke ◽  
Ru Li ◽  
Ruifeng Tian
Keyword(s):  
Steam Generator ◽  
High Speed ◽  
Nuclear Power ◽  
Separation Efficiency ◽  
Inertial Force ◽  
High Speed Photography ◽  
Separation Mechanism ◽  
The Relationship ◽  
Plate Separator

Abstract The steam generator is an important part of the nuclear power plant, and the corrugated plate separator plays the important role of drying steam in the steam generator to improve power generation efficiency and protect the safety of the system. The separation mechanism of the corrugated plate separator is relatively complicated. The droplets are moved by the drag force of the steam and gravity in the corrugated plate separator, and captured by the wall of the corrugated plate separator. When the velocity is increased, the inertial force of droplet is increased, so that the droplet is more easily captured by the wall of the corrugated plate separator, and the separation efficiency of the corrugated plate separator is increased. In this paper, the phenomenon of droplet impact on the inclined wall is studied by high-speed photography technology, and the cause and mechanism of the phenomenon are analyzed. By analyzing the spreading and splashing on the droplets impacting on the inclined wall, the relationship between the inclination angle of the droplet impacting on the inclined wall and the spreading is obtained, and the influence of droplets with different Weber numbers, and dry and wetted walls were analyzed, which provide a basis for the optimization of the corrugated plate separator.

An Experimental Study on Saturated Liquid Nitrogen’s Boiling Under Transient Pulsed Laser Irradiation

2004 ◽  
Author(s):  
Zhaoyi Dong ◽  
Xiulan Huai ◽  
G.-X. Wang
Keyword(s):  
Temperature Variation ◽  
High Speed ◽  
Short Pulse ◽  
Heating Surface ◽  
High Heat ◽  
Measuring System ◽  
Experimental Result ◽  
High Speed Photography ◽  
High Heat Flux ◽  
Explosive Boiling

Liquid nitrogen (LN2) was widely applied in many areas, but researches on the boiling behavior under the transient high heat flux have not been reported. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2’s boiling behavior under such conditions. At the same time, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experimental result disclosed that at the earlier stage of laser heating, an explosive boiling would happen within LN2. After the newly-defined changeover time, the conventional boiling behavior would follow. Therefore the changeover time became an important index to distinguish these two kinds of boiling behaviors. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of bubbles in explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism.

INFLUENCE OF SURFACE FREE ENERGY ON ADHESION OF CrN THIN FILM DEPOSITED BY AIP METHOD

2012 ◽  
Vol 06 ◽  
pp. 509-514 ◽  
Author(s):  
HIKARU NOUDA ◽  
HIROATSU ODA ◽  
DAISUKE YONEKURA ◽  
RI-ICHI MURAKAMI
Keyword(s):  
Thin Film ◽  
Free Energy ◽  
Surface Free Energy ◽  
High Speed ◽  
Gas Flow ◽  
Sessile Drop ◽  
Ion Bombardment ◽  
Polar Component ◽  
Scratch Testing ◽  
The Relationship

The purpose of this study is to examine the relationship between adhesion of CrN thin film and the surface free energy of substrate. CrN film was deposited on JIS SKH2 high speed tool steel by arc ion plating (AIP) method. The surface free energy of the substrate was measured with/without ion bombardment process using nitrogen and argon gas under various gas flow rate before CrN deposition. The surface free energy was measured by the sessile drop method using distilled water and methylene iodide. The adhesion was evaluated by scratch testing and the relationship between a critical load and the surface free energy in each ion bombardment condition was discussed. As a result, it was found that the adhesion increased with decreasing the surface free energy, in particular the polar component strongly affects the adhesion.

Vibration Mechanisms of a Heated Rod Due to Subcooled Boiling Flow

2006 ◽  
Author(s):  
M. R. Nematollahi ◽  
M. H. Akbari
Keyword(s):  
Quantitative Estimate ◽  
High Speed ◽  
Bubble Formation ◽  
Heating Surface ◽  
High Speed Photography ◽  
Subcooled Boiling ◽  
Bubble Behavior ◽  
Boiling Flow ◽  
Excitation Force ◽  
Power Densities

Vibration characteristics of subcooled boiling flow on thin and long structures such as a heating rod were recently investigated by the authors. The results show that the intensity of the subcooled boiling-induced vibration (SBIV) was influenced strongly by the conditions of subcooling temperature, linear power density and flow velocity. Implosive bubble formation and collapse are the main nature of subcooled boiling, and their behavior are the only sources to originate SBIV. Therefore, in order to explain the phenomenon of SBIV, it is essential to obtain reliable information about bubble behavior in subcooled boiling conditions. This was investigated at different conditions of coolant subcooling temperatures of 25 to 75°C, coolant flow velocities of 16 to 53 cm/s, and linear power densities of 100 to 600 W/cm. High speed photography at 13,500 frames per second was performed at these conditions. The results show that even at the highest subcooling condition, the absolute majority of bubbles collapse very close to the surface after detaching from the heating surface. Based on these observations, a simple model of surface tension and momentum change is introduced to offer a rough quantitative estimate of the force exerted on the heating surface. The formation of a typical bubble in subcooled boiling is predicted to exert an excitation force in the order of 10−4 N.

On the Influence of Heating Surface Structure on Bubble Detachment in Sub-Cooled Nucleate Boiling Flows

2006 ◽  
Author(s):  
Wen Wu ◽  
Peipei Chen ◽  
Barclay G. Jones ◽  
Ty A. Newell
Keyword(s):  
Surface Structure ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Bubble Detachment ◽  
Lift Off ◽  
R 134A ◽  
Bubble Movement

This research examines the influence of heating surface structure on bubble detachment, which includes bubble departure and bubble lift-off, under sub-cooled nucleate boiling condition, in order to obtain better understanding to the bubble dynamics on horizontal flat heat exchangers. Refrigerant R-134a is chosen as a simulant fluid due to its merits of having smaller surface tension, reduced latent heat, and lower boiling temperature than water. Experiments were run with varying experimental parameters e.g. pressure, inlet sub-cooled level, and flow rate, etc. High speed digital images at frame rates up to 4000 frames/s were obtained, showing characteristics of bubble movement. Bubble radius and center coordinates were calculated via Canny’s algorithm for edge detection and Fitzgibbon’s algorithm for ellipse fitting. Results were compared against the model proposed by Klausner et al. for prediction of bubble detachment sizes. Good overall agreement was shown, with several minor modifications and suggestions made to the assumptions of the model.

Experimental Study on Bubble Collapse Near a Solid Boundary

2016 ◽  
Author(s):  
Shuai Zhang ◽  
Shiping Wang ◽  
Yunlong Liu
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Bubble Radius ◽  
Water Layer ◽  
Lower Surface ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
Liquid Jet ◽  
High Speed Photography ◽  
Generating Method

In this paper, we present a high-voltage electric-spark bubble-generating method which can generate a bubble with its maximum radius reaching up to ∼35 mm at a room pressure. Vertical migration and clear liquid jet inside the bubble are captured by a high speed photography. With this method, a series of experiments on bubbles collapse above a solid boundary are carried out under different non-dimensional standoff distances γ (= s/Rm, where s is the vertical distance from the bubble center to the solid boundary and Rm denotes the maximum bubble radius). It is found when bubble is extremely close to the solid boundary (γ < 0.6), the lower surface of the bubble will cling to the solid boundary, which causes the cone-shaped liquid jet to impact on solid boundary directly without buffering of the water layer. With the increase of γ, the bottom of the bubble is gradually away from the solid boundary with an increasing curvature, but the jet inside the bubble remains conical all along. The speed of the jet tip and the migration of the bubble top are also discussed subsequently, aiming to provide a reference for the numerical study. Finally, the critical value of γ is investigated, at which the effect of the buoyancy will compensate the attraction of the solid boundary when the buoyancy parameter of bubble is bout 0.06.

Cavitation erosion by single laser-produced bubbles

1998 ◽  
Vol 361 ◽  
pp. 75-116 ◽  
Author(s):  
A. PHILIPP ◽  
W. LAUTERBORN
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Cavitation Erosion ◽  
Bubble Radius ◽  
Solid Boundary ◽  
Material Surface ◽  
High Speed Photography ◽  
Single Laser ◽  
The Moment ◽  
The Impact

In order to elucidate the mechanism of cavitation erosion, the dynamics of a single laser-generated cavitation bubble in water and the resulting surface damage on a flat metal specimen are investigated in detail. The characteristic effects of bubble dynamics, in particular the formation of a high-speed liquid jet and the emission of shock waves at the moment of collapse are recorded with high-speed photography with framing rates of up to one million frames/s. Damage is observed when the bubble is generated at a distance less than twice its maximum radius from a solid boundary (γ=2, where γ=s/Rmax, s is the distance between the boundary and the bubble centre at the moment of formation and Rmax is the maximum bubble radius). The impact of the jet contributes to the damage only at small initial distances (γ[les ]0.7). In this region, the impact velocity rises to 83 m s−1, corresponding to a water hammer pressure of about 0.1 GPa, whereas at γ>1, the impact velocity is smaller than 25 m s−1. The largest erosive force is caused by the collapse of a bubble in direct contact with the boundary, where pressures of up to several GPa act on the material surface. Therefore, it is essential for the damaging effect that bubbles are accelerated towards the boundary during the collapse phases due to Bjerknes forces. The bubble touches the boundary at the moment of second collapse when γ<2 and at the moment of first collapse when γ<1. Indentations on an aluminium specimen are found at the contact locations of the collapsing bubble. In the range γ=1.7 to 2, where the bubble collapses mainly down to a single point, one pit below the bubble centre is observed. At γ[les ]1.7, the bubble shape has become toroidal, induced by the jet flow through the bubble centre. Corresponding to the decay of this bubble torus into multiple tiny bubbles each collapsing separately along the circumference of the torus, the observed damage is circular as well. Bubbles in the ranges γ[les ]0.3 and γ=1.2 to 1.4 caused the greatest damage. The overall diameter of the damaged area is found to scale with the maximum bubble radius. Owing to the possibility of generating thousands of nearly identical bubbles, the cavitation resistance of even hard steel specimens can be tested.

A Study of Bubble Departure in Forced-Convection Boiling

1968 ◽  
Vol 90 (2) ◽  
pp. 223-230 ◽  
Author(s):  
N. Koumoutsos ◽  
R. Moissis ◽  
A. Spyridonos
Keyword(s):  
Forced Convection ◽  
Liquid Flow ◽  
High Speed ◽  
Water System ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Spherical Bubble ◽  
Velocity Relationship ◽  
Departure Size

Visual observations in a boiling liquid flow indicate that, as the flow velocity is increased, the size of bubbles leaving the heating surface decreases. The purpose of this investigation is to arrive at a criterion for bubble departure in forced-convection nucleate boiling. Photographic studies indicate that a little before departure a “neck” is formed joining the almost spherical bubble to the heating surface. From a consideration of the hydrodynamic stability of the bubble-and-neck model, the departure-size-to-velocity relationship may be predicted. Measured departure radii in a forced-convection boiling water system taken by means of high-speed photography are satisfactorily correlated with the results derived analytically.

Crack divergence phenomena in tempered glass

2020 ◽  
Vol 13 (3) ◽  
pp. 115-129
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Optimal Design ◽  
High Speed ◽  
Glass Plate ◽  
Acute Angle ◽  
Divergence Angle ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Thick Glass

High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.

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