Dynamic Behavior of a Small Water Droplet Impact Onto a Heated Hydrophilic Surface

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
El-Sayed R. Negeed ◽  
M. Albeirutty ◽  
Sharaf F. AL-Sharif ◽  
S. Hidaka ◽  
Y. Takata
Keyword(s):  
Dynamic Behavior ◽  
Water Droplet ◽  
High Speed ◽  
Heated Surface ◽  
Droplet Diameter ◽  
Video Camera ◽  
Surface Wettability ◽  
Hydrodynamic Characteristics ◽  
Small Water ◽  
Hot Surface

The aim of this study is to investigate the influence of the surface wettability on the dynamic behavior of a water droplet impacting onto a heated surface made of stainless steel grade 304 (Sus304). The surface wettability is controlled by exposing the surfaces to plasma irradiation for different time periods (namely, 0.0, 10, 60, and 120 s). The experimental runs were carried out by spraying water droplets on the heated surface where the droplet diameter and velocity were independently controlled. The droplet behavior during the collision with the hot surface has been recorded with a high-speed video camera. By analyzing the experimental results, the effects of surface wettability, contact angle between impacting droplet and the hot surface, droplet velocity, droplet size, and surface superheat on the dynamic behavior of the water droplet impacting on the hot surface were investigated. Empirical correlations are presented describing the hydrodynamic characteristics of an individual droplet impinging onto the heated hydrophilic surfaces and concealing the affecting parameters in such process.

The Effect of Water Content Diameter on the Structure of Light Oil-Water Emulsion Spray Flame

2007 ◽  
Author(s):  
Manabu Fuchihata ◽  
Shuko Takeda ◽  
Tamio Ida
Keyword(s):  
Water Content ◽  
Water Droplet ◽  
High Speed ◽  
Droplet Diameter ◽  
Flame Structure ◽  
Video Camera ◽  
Water Emulsion ◽  
Light Oil ◽  
Oil Water ◽  
Co Emission

Microexplosions of light oil-water emulsified fuel droplets were successfully documented using a high-speed video camera with laser illumination. The local frequency of the explosion occurrence, temperature profile and exhaust gas emissions were measured in spray flames of water-in-oil type emulsion formed using an air-assist atomizer with a ring pilot burner. Those results indicate that the flame structure changes as the water droplet diameter in the emulsion fuel was varied, even if the fuel components and their fractions were same. When the fuel includes the water droplet, whose median diameter was about 75μm, HC and CO emission were reduced as compared to those for the fuel of smaller water droplet content. It is probable that if the water droplet diameter is uniform, avalanching microexplosions occur at certain local region in the flame, and the water content vaporizes almost at once and extinguishes the flame. It leads to HC and CO emission increase. When the water droplet diameters are large, atomizer atomizes those; therefore, emulsion droplets include various size of water droplet in the flame. Consequently, the avalanching microexplosion occurrence is avoided, and HC and CO emissions are reduced.

Subcooled Boiling of Surfactant Solutions

2000 ◽  
Author(s):  
G. Hetsroni ◽  
M. Gurevich ◽  
A. Mosyak ◽  
R. Rozenblit ◽  
L. P. Yarin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Speed ◽  
Heated Surface ◽  
Pure Water ◽  
Video Camera ◽  
Subcooled Boiling ◽  
Bubble Behavior ◽  
Boiling Hysteresis

Abstract During subcooled boiling of pure water and water with cationic surfactants, the motion of bubbles and the temperature of the heated surface were recorded by both a high-speed video camera and an infrared radiometer. The results show that the bubble behavior and the heat transfer mechanism for the surfactant are quite different from those of clear water. Bubbles formed in Habon G solutions were much smaller man those in water and the surface was covered with them faster. Boiling hysteresis is found for degraded solutions. Dependencies of heat transfer coefficient for various solutions were obtained and compared. The boiling curves of surfactant are quite different from the boiling curve of pure water. Experimental results demonstrate that the heat transfer coefficient of the boiling process can be enhanced considerably by the addition of a small amount of Habon G. The experiments show that the limitations of the ER technique with respect to frequency response are outweighed by its unique capacity to measure wall temperature distribution with high spatial resolution over an area encompassing many nucleation sites and over long periods.

Behavior of Bubble in Small Water Tank Used for Food Processing Using Underwater Shock Wave

2011 ◽  
Vol 673 ◽  
pp. 225-230 ◽  
Author(s):  
Hideki Hamashima ◽  
Manabu Shibuta ◽  
Shigeru Itoh
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Food Processing ◽  
High Speed ◽  
Underwater Explosion ◽  
Video Camera ◽  
Experimental Result ◽  
Water Tank ◽  
Underwater Shock Wave ◽  
Small Water

The food processing technology using a shock wave can prevent deterioration of the food by heat because it can process food in a short time. Generally, since the shock wave used for food processing is generated by underwater explosion, the load of a shock wave to the food becomes very complicated. Therefore, in order to process safely, it is important to clarify the behaviors of the shock wave and the bubble pulse generated by underwater explosion. In this research, in order to investigate the behavior of the shock wave in the water tank used for food processing, the optical observation experiment and the numerical simulation were performed. In the experiment, the shock wave generated by underwater explosion was observed with the high-speed video camera. The numerical simulation about the behavior of bubble pulse was performed using analysis software LS-DYNA. Comparing and examining were performed about the experimental result and the numerical simulation result. The result of the numerical simulation about the behavior of the shock wave generated by underwater explosion and the shock wave generated by the bubble pulse and the bubble pulse was well in agreement with the experimental result.

Dynamic Behavior of Liquid Mercury Droplets Colliding with a Solid Surface

2014 ◽  
Vol 566 ◽  
pp. 391-396
Author(s):  
Takashi Naoe ◽  
Masatoshi Futakawa
Keyword(s):  
Surface Tension ◽  
Dynamic Behavior ◽  
Solid Surface ◽  
High Speed ◽  
Droplet Diameter ◽  
High Surface ◽  
Quartz Plate ◽  
Bubble Collapse ◽  
Fundamental Study ◽  
Liquid Mercury

The dynamic behavior of liquid mercury and water droplets colliding with a solid surface were precisely examined as part of a fundamental study for investigating the behavior of a liquid microjet emitted as a result of a cavitation bubble collapse in mercury. Liquid droplets were collided with a quartz plate by the free-fall method, and the colliding and spreading behaviors of the liquids were observed using a high-speed video camera. In the case of mercury droplets, the spreading, recoiling, and jump-up phenomena resulting from the high surface tension of mercury were observed. The ratio of the maximum spreading diameter,Dmax, to the initial droplet diameter,D0, was investigated by parametrically changing the colliding velocity and tilt-angle of the quartz plate. The result showed that the ratioDmax/D0was well correlated with the Weber number, which is defined as a function of the colliding velocity and surface tension, independent of the liquid considered.

An Experimental Study of the Vaporization Characteristics of Diesel-Benzyl Azides Blend Droplets

2013 ◽  
Author(s):  
Kai Han ◽  
Geng Fu ◽  
Changlu Zhao ◽  
Bolan Liu ◽  
Shibo Ma
Keyword(s):  
Experimental Study ◽  
Ambient Temperature ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Droplet Diameter ◽  
Video Camera ◽  
Initial Droplet ◽  
High Speed Video Camera ◽  
Combustion Duration ◽  
Suspended Droplet

An experimental study of diesel-benzyl azides blend droplets vaporization characteristics was carried out to study the reasons of diesel-benzyl azides blend shortened combustion duration using suspended droplet device and a high-speed video camera. Experiments were performed at atmospheric pressure, ambient temperature range 480–933 K, and initial droplet diameter of 0.98, 1.42, 1.88 mm. The results show a shorten in diesel-benzyl azides blend droplet lifetime by 10% compared to diesel droplet at 1.42 mm initial droplet diameter and 933 K ambient temperature companion to puffing. The above results support the original idea of designing diesel-benzyl azides blend where the energy released by the decomposition of azides improves the vaporization and the release of nitrogen leads to the breakup of the droplet. In addition, it is observed that the blend lifetime decrease with increasing ambient temperature compared to diesel droplet lifetime. More nitrogen is released and the expansion of bubbles is more violent with increasing initial droplet diameter.

scholarly journals Enhancement of Sensitivity and Accuracy of Micro/Nano Water Droplets Detection Using Galvanic-Coupled Arrays

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4500 ◽  
Author(s):  
Rekha Goswami Shrestha ◽  
Tatsuya Ando ◽  
Yukihiro Sakamoto ◽  
Jin Kawakita
Keyword(s):  
Contact Angle ◽  
Water Droplet ◽  
High Speed ◽  
Current Response ◽  
Water Droplets ◽  
Galvanic Current ◽  
Moisture Sensor ◽  
Average Value ◽  
Small Water ◽  
Working Principle

A moisture sensor has been reported that detects invisibly small water droplets and distinguishes their particle size with high accuracy and high speed. This sensor uses narrow lines of dissimilar metals as electrodes, arranged with gaps of 0.5 to 10 μm. The working principle for this sensor is that it measures the galvanic current generated when a water droplet forms a bridge-like structure between the electrodes. In addition, the surface of the sensor was controlled by using hydrophilic polymer, GL, and hydrophobic polymer, PMMA. The study of the relationship between the contact angle, projected area of water droplets and current response from the sensor with a modified surface showed that in the case of GL, the contact angle was small (wettability increased) and the average value and distribution of the projected water droplet area and the sensor’s response increased. This enhanced the sensor’s sensitivity. On the other hand, in the case of PMMA, the contact angle was large (wettability decreased), the area of the water droplet and its distribution became small and the accuracy of discriminating the water droplet’s diameter by the sensor enhanced. Therefore, by rendering sensor’s surface hydrophilic and hydrophobic, the sensitivity and accuracy of the sensor could be enhanced.

Dynamics of a Water Droplet on the Heated Surface of Nano- and Micro-Structures

2012 ◽  
Author(s):  
Seol Ha Kim ◽  
Ho Seon Ahn ◽  
Joonwon Kim ◽  
Moo Hwan Kim
Keyword(s):  
Water Droplet ◽  
High Speed ◽  
Zirconium Alloy ◽  
Liquid Droplet ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Complete Wetting ◽  
Structured Surfaces ◽  
Bare Surface

In this study, we investigated the dynamic behavior of a water droplet near the Leidenfrost point (LFP) of bare and modified zirconium alloy surfaces with bundles of nanotubes (∼10–100 nm) or micro mountain-like structures using high-speed photography. A deionized water droplet (6 μL) was dropped onto the sample surfaces (20 × 25 × 0.7 mm) that were heated to temperatures ranging from 250°C to the LFP. The modified zirconium alloy surfaces showed complete wetting and well-spread features at room temperature due to strong liquid spreading by the structure. The meniscus of the liquid droplet on the structured surface experienced more vigorous dynamics with intensive nucleate boiling, compared with the clean, bare surface. The cutback phenomenon was observed on the bare surface; however, the structured surfaces showed a water droplet “burst”. We observed that the LFPs were 449°C, 522°C, and 570°C, corresponding to the bare, micro-, and nano-structures, respectively.

Liquid marble and water droplet interactions and stability

Soft Matter ◽  
2015 ◽  
Vol 11 (39) ◽  
pp. 7728-7738 ◽  
Author(s):  
Kazuyuki Ueno ◽  
Ghislain Bournival ◽  
Erica J. Wanless ◽  
Saori Nakayama ◽  
Emma C. Giakoumatos ◽  
...  
Keyword(s):  
Water Droplet ◽  
High Speed ◽  
Video Camera ◽  
Water Droplets ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Liquid Marble

The interactions between two individual water droplets were investigated in air using a combination of coalescence rig and high speed video camera.

The transitions of time-independent spreading diameter and splashing angle when a droplet train impinging onto a hot surface

RSC Advances ◽  
2016 ◽  
Vol 6 (17) ◽  
pp. 13644-13652 ◽  
Author(s):  
Lu Qiu ◽  
Swapnil Dubey ◽  
Fook Hoong Choo ◽  
Fei Duan
Keyword(s):  
High Temperature ◽  
Water Droplet ◽  
High Speed ◽  
High Speed Camera ◽  
Hot Surface

The hydrodynamic patterns of the impingement of a water droplet train on a high temperature substrate are captured with a high-speed camera, and then analyzed.

scholarly journals EXPERIMENTAL STUDY ON THE PHENOMENA ON THE SUCCESSIVE DROPLETS IMPACTING HOT COPPER SURFAC

2019 ◽  
Vol 24 (2) ◽  
pp. 129-142
Author(s):  
Arif Widyatama ◽  
Akmal Irfan Majid ◽  
Teguh Wibowo ◽  
Deendarlianto Deendarlianto ◽  
Samsul Kamal
Keyword(s):  
Image Processing ◽  
High Speed ◽  
Droplet Diameter ◽  
Video Camera ◽  
Processing Technique ◽  
Image Processing Technique ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Diameter Droplet ◽  
Apex Height

This study was aimed at investigating the phenomena and interactions between water droplets and hot metal surfaces using an experimental method. In this study, the droplet was dropped from 50 mm from the top of the metal surface with a frequency of 8.5 droplets per second. The observed droplet diameter was 3.12 mm. The metal used was copper with a surface temperature between 110-240 ° C. High speed video camera with a speed of 2000 fps was used to record visual data. Then the image processing technique was applied to calculate the change in droplet diameter. The results show that at low temperatures, droplets tend to maintain their initial position of contact with fluctuating deformations. While at high temperatures, a bounce phenomenon occurs which results in collisions between droplets being imperfect. Visualization results can reveal the complete change in the droplet geometry in the form of spreading ratio and complete apex height. The temperature of 140° C is the initial transition area for phenomena that result in droplets has no contact with hot surfaces so that the process of heat transfer between surfaces is inhibited.STUDI EKSPERIMEN PADA FENOMENA SUCCESSIVE DROPLETS MENUMBUK PERMUKAAN TEMBAGA PANASPenelitian ini bertujuan untuk mempelajari fenomena dan interaksi antara tetesan air (droplet) dan permukaan logam panas dengan metode eksperimental. Pada penelitian ini, droplet dijatuhkan dari posisi 50 mm dari atas permukaan logam dengan frekuensi 8,5 droplet per detik. Diameter droplet yang diamati sebesar 3,12 mm. Logam yang digunakan adalah tembaga dengan temperatur permukaan di antara 110-240° C. High speed video camera dengan kecepatan 2000 fps digunakan untuk merekam data visual. Teknik image processing diaplikasikan untuk menghitung perubahan diameter droplet. Hasil penelitian menunjukkan bahwa pertama, pada temperatur rendah, droplet cenderung mempertahankan posisi awal kontak dengan perubahan bentuk yang fluktuatif. Kedua, temperatur tinggi, terjadi fenomena bouncing yang mengakibatkan tumbukan antar droplet menjadi tidak sempurna. Hasil visualisasi dapat mengungkap perubahan geometri droplet berupa spreading ratio dan apex height secara lengkap. Dari penelitian ini juga diketahui bahwa temperatur 140°C menjadi daerah transisi awal terjadinya fenomena yang mengakibatkan droplet tidak bersinggungan dengan permukaan panas sehingga proses perpindahan kalor antar permukaan terhambat.

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