scholarly journals Optical Technique to Measure Transient Interface Temperature During Droplet Impingement on a Cooled Surface

2000 ◽  
Author(s):  
Y. Li ◽  
J. P. Longtin
Keyword(s):  
Laser Beam ◽  
Temperature Change ◽  
Temporal Resolution ◽  
Solid Surface ◽  
Liquid Droplet ◽  
Liquid Interface ◽  
Temperature History ◽  
Interface Temperature ◽  
Measured Temperature ◽  
Liquid Droplets

Abstract Liquid droplets impinging upon a solid surface are present in many diverse and important engineering and scientific applications. Examples include impingement cooling of surfaces, condensation phenomena in which liquid droplets fall and strike a surface, vigorous mixing of gas-liquid systems, and in manufacturing, e.g., pouring a liquid material onto a cooled surface or mold to form objects. The accurate measurement of the solid-liquid interface temperature of a liquid droplet impinging on a solid surface is extremely difficult to do using traditional, contact-based techniques, however. This work presents a laser-based technique that is capable of resolving the transient interface temperature change as a liquid droplet strikes a surface. The measurement records changes in reflected light from the liquid-solid interface, which is correlated to temperature change. In this work, the substrate is BK7 glass or quartz. The liquid falls from a height of several centimeters, while the laser beam is sent through the transparent solid material from the underside for the measurement. Results are presented for water and glycerin, with good agreement found between predicted and measured temperature histories. Additional features of the technique include extremely fast temporal resolution, which is limited only by the speed of the light-capturing electronics. A temporal resolution of 1 microsecond is readily obtainable with inexpensive electronics. Also, the use of a high-quality Gaussian laser beam from, e.g., a HeNe laser or a single-mode fiber can be focused to a spot size ranging from several millimeters to 10 microns in diameter at the liquid interface, thus providing a wide variety of spatial resolutions, including those in the microscale. Finally, an array of interrogation beams can be employed simultaneously to monitor the spatial temperature history of a droplet as it spreads and cools once striking the surface. Both present and future applications of the technique will be discussed in the talk.

Bubble Formation at Impingement of a Liquid Droplet on a Solid Surface

2000 ◽  
Author(s):  
Hitoshi Fujimoto ◽  
Tomoyuki Ogino ◽  
Osamu Takahashi ◽  
Hirohiko Takuda ◽  
Natsuo Hatta
Keyword(s):  
Solid Surface ◽  
Liquid Droplet ◽  
Droplet Diameter ◽  
Bubble Formation ◽  
Liquid Droplets ◽  
Vapor Bubbles ◽  
Experimental Conditions ◽  
Video Cameras ◽  
The Moment ◽  
The Impact

Abstract The collision of liquid droplets with a solid has been studied experimentally. The time evolution of the liquid/solid contact area as well as the shape of droplets has been observed by means of a flash-photographic method using two video cameras. It has been found that some air between the solid surface and the incoming droplet is entrapped at the moment of impact. In the case where the solid temperature is high (= 450 °C), numerous vapor bubbles appear at the liquid/solid interface after the collision. The bubble formation due to the entrapment of air has been examined for various experimental conditions. Water, and ethanol are used as test liquid. The droplet diameter is 2.4 mm for water and 1.9 mm for ethanol. The impact velocity varies from 0.8 to 3.1 m/s. The entrapment of air has been observed for both liquids under all conditions in the present study.

Emission of Liquid Droplets From the Interface of Bidrops Pulled by a Ferrofluid in a Microchannel

2009 ◽  
Author(s):  
Yuichi Shibata ◽  
Kota Takamine ◽  
Masahiro Kawaji
Keyword(s):  
Liquid Droplet ◽  
Contact Angles ◽  
Liquid Interface ◽  
Liquid Droplets ◽  
Liquid Slug ◽  
Immiscible Liquids ◽  
Static Contact ◽  
Circular Microchannel ◽  
And Behavior ◽  
The Relationship

The field of microfluidics is developing with advances in biotechnology and μ-TAS technologies. In various devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. By using a ferrofluid, the flow of a liquid or gas in a microchannel can be controlled by the driving power exerted on the ferrofluid. In a previous study, an unsteady flow of a liquid slug caused by the driving force exerted by the ferrofluid was investigated in a 200μm circular microchannel. The velocity of the ferrofluid was found to be affected by the physical properties of the liquids being pulled, such as the dynamic and static contact angles, surface tension and kinematic viscosity of the liquid slugs. At sufficiently high velocities of the ferrofluid, emission of a liquid droplet from the liquid-liquid interface was observed. In the present study, combinations of various liquids with the ferrofluid were examined in two microchannels (130μm and 200μm diameter). The relationship between the emission of liquid droplets and interfacial fluctuation of the bidrops was investigated experimentally and analytically. The emission of liquid droplets from the interface and behavior of the interface were observed using liquids of different viscosities. The interfacial shape changed continuously until a liquid droplet was emitted from the interface of the immiscible liquids. When the ferrofluid velocity was increased, necking of the liquid-liquid interface occurred continuously and some liquid droplets were emitted from the interface. We could study the characteristics of emission of liquid droplets from the interfacial variation.

scholarly journals Solid–Liquid Interface Temperature Measurement of Evaporating Droplet Using Thermoresponsive Polymer Aqueous Solution

2021 ◽  
Vol 11 (8) ◽  
pp. 3379
Author(s):  
Hyung Ju Lee ◽  
Chan Ho Jeong ◽  
Dae Yun Kim ◽  
Chang Kyoung Choi ◽  
Seong Hyuk Lee
Keyword(s):  
Refractive Index ◽  
Heated Surface ◽  
Liquid Interface ◽  
Interface Temperature ◽  
Thermoresponsive Polymer ◽  
Temperature Deviation ◽  
Line Region ◽  
Optical And Mechanical Properties ◽  
Solid Liquid Interface ◽  
Solid Liquid

The present study aims to measure the solid–liquid interface temperature of an evaporating droplet on a heated surface using a thermoresponsive polymer. Poly(N-isopropylacrylamide) (pNIPAM) was used owing to its sensitive optical and mechanical properties to the temperature. We also measured the refractive index variation of the pNIPAM solution by using the surface plasmon resonance imaging (SPRi). In particular, the present study proposed a new method to measure the solid–liquid interface temperature using the correlation among reflectance, refractive index, and temperature. It was found that the reflectance of a pNIPAM solution decreased after the droplet deposition. The solid–liquid interface temperature, estimated from the reflectance, showed a lower value at the center of the droplet, and it gradually increased along the radial direction. The lowest temperature at the contact line region is present because of the maximum evaporative cooling. Moreover, the solid–liquid interface temperature deviation increased with the surface temperature, which means solid–liquid interface temperature should be considered at high temperature to predict the evaporation flux of the droplet accurately.

Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Hirotoshi Sasaki ◽  
Yuka Iga
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Erosion Rate ◽  
Liquid Droplet ◽  
Material Surface ◽  
Liquid Droplets ◽  
Fluid Machinery ◽  
Droplet Impingement ◽  
Surface Liquid ◽  
Droplet Impingement Erosion

This study explains why the deep erosion pits are formed in liquid droplet impingement erosion even though the droplets uniformly impinge on the entire material surface. Liquid droplet impingement erosion occurs in fluid machinery on which droplets impinge at high speed. In the process of erosion, the material surface becomes completely roughened by erosion pits. In addition, most material surface is not completely smooth and has some degree of initial roughness from manufacturing and processing and so on. In this study, to consider the influence of the roughness on the material surface under droplet impingement, a numerical analysis of droplets impinging on the material surface with a single wedge and a single bump was conducted with changing offsets between the droplet impingement centers and the roughness centers on each a wedge bottom and a bump top. As results, two mechanisms are predicted from the present numerical results: the erosion rate accelerates and transitions from the incubation stage to the acceleration stage once roughness occurs on the material surface; the other is that deep erosion pits are formed even in the case of liquid droplets impinging uniformly on the entire material surface.

Simulation of Impaction Between Liquid Droplet and Solid Particles Based on SPH Method

2014 ◽  
Author(s):  
Shuai Meng ◽  
Qian Wang ◽  
Rui Yang
Keyword(s):  
Surface Tension ◽  
Solid Particle ◽  
Liquid Droplet ◽  
Particle Interaction ◽  
Solid Particles ◽  
Seed Particle ◽  
Liquid Droplets ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Spray Granulation

The phenomenon of impaction between liquid droplets and solid particles is involved in many scientific problems and engineering applications, such as impaction between sprayed droplet and solid particles in limestone injection desulfurization system and the collision between a droplet of the liquid to be granulated and a seed particle in fluidized bed spray granulation process. There are a lot of factors affected this phenomenon: droplet and particle size, momentum of both liquid droplet and solid particles, materials, surface conditions of the solid particles and so on. However the experimental or numerical researches have been done mostly pay attention to Specific application or process, so the impaction phenomenon has not been through studied, for example how different factors affected the impaction process with its effect on different applications. This paper focuses on the basic issue of interaction between droplet and solid particles. Three main factors were considered: ratio of diameter between the droplet and solid particle, relative velocity and the surface tension (including the contact angle between droplet and solid particle). All the study is based on simulation using SPH (smoothed particle hydrodynamics) method, and the surface tension is simulated by particle-particle interaction.

Nucleation Processes in Large Scale Vapor Explosions

1979 ◽  
Vol 101 (2) ◽  
pp. 280-287 ◽  
Author(s):  
R. E. Henry ◽  
H. K. Fauske
Keyword(s):  
Large Scale ◽  
Interface Temperature ◽  
Liquid Droplets ◽  
Contact Interface ◽  
Vapor Cavity ◽  
Spontaneous Nucleation ◽  
System Pressure ◽  
Nucleation Model ◽  
Vapor Explosions ◽  
Cold Liquid

A spontaneous nucleation model is proposed for the mechanisms which lead to explosive boiling in the free contacting mode. The model considers that spontaneous nucleation cannot occur until the thermal boundary layer is sufficiently thick to support a critical size vapor cavity, and that significant bubble growth requires an established pressure gradient in the cold liquid. This results in a prediction that, for an interface temperature above the spontaneous nucleation limit, large cold liquid droplets will remain in film boiling due to coalescence of vapor nuclei, whereas smaller droplets will be captured by the hot liquid surface and rapidly vaporize, which agrees with the experimental observations. The model also predicts that explosions are eliminated by an elevated system pressure or a supercritical contact interface temperature, and this is also in agreement with experimental data.

scholarly journals Semidiscrete central difference method in time for determining surface temperatures

2005 ◽  
Vol 2005 (3) ◽  
pp. 393-400 ◽  
Author(s):  
Zhi Qian ◽  
Chu-Li Fu ◽  
Xiang-Tuan Xiong
Keyword(s):  
Difference Method ◽  
Heat Conduction Problem ◽  
A Priori ◽  
Inverse Heat Conduction Problem ◽  
The Body ◽  
Temperature History ◽  
Measured Temperature ◽  
Central Difference ◽  
Approximation Solution ◽  
Computational Effect

We consider an inverse heat conduction problem (IHCP) in a quarter plane. We want to know the distribution of surface temperature in a body from a measured temperature history at a fixed location inside the body. This is a severely ill-posed problem in the sense that the solution (if exists) does not depend continuously on the data. Eldén (1995) has used a difference method for solving this problem, but he did not obtain the convergence atx=0. In this paper, we gave a logarithmic stability of the approximation solution atx=0under a stronger a priori assumption‖u(0,t)‖p≤Ewithp>1/2. A numerical example shows that the computational effect of this method is satisfactory.

Visualization of Cells at the Solid-microbe Interface Using Confocal Reflection Microscopy With Index-matching Materials

2021 ◽  
Author(s):  
Chigusa Okano ◽  
Tomohiro Hirayama ◽  
Nobuhiko Nomura ◽  
Yutaka Yawata
Keyword(s):  
Solid Surface ◽  
Biofilm Formation ◽  
Liquid Interface ◽  
Direct Visualization ◽  
Microbial Cells ◽  
Low Contrast ◽  
Index Matching ◽  
Transformation Methods ◽  
Solid Liquid Interface ◽  
Solid Liquid

Abstract Herein, we demonstrated that the use of index-matching materials (IMM) allows direct visualization of microbial cells maintained at a solid-liquid interface through confocal reflection microscopy (CRM). The RI mismatch induces a background reflection at the solid-liquid interface, which dwarfs the reflection signals from the cells and results in low-contrast images. We found that the IMM sufficiently suppressed the background reflection at the solid-liquid interface, facilitating the imaging of microbes at the solid surface using CRM. Further, we succeeded in temporal imaging of initial biofilms directly colonizing the IMM with CRM in a tag free fashion, and thus, it is highly advantageous for probing the dynamics of biofilm formation, along with visualization of environmental organisms and newly isolated bacteria, for which transformation methods are difficult to establish.

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