Effect of particle size and concentration on bubble size distribution and aspect ratio in a counter-current microstructured bubble column

Ritesh Prakash,Subrata Kumar Majumder 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.90 No.-

The experimental study of bubble size and its distribution and bubble aspect ratio in a dense bubblyflowconditions remains challenging. The present work enunciates the bubble size and its distribution, andbubble aspect ratio in two (air-water) and three-phase (air-water-coal particle) in a counter-currentmicrostructured bubble column with and without surfactant. The effects of dispersed and continuousphase velocity, solid loading, and solid size are investigated. The results show that an increase in thedispersed phase velocity, the particle concentration led to a rise in Sauter mean bubble diameter, while, itis decreased with an increase in the continuous phase velocity and particle size. The aspect ratio of thebubble decreases as the Eötovos number increases. Bubble size distributions follow the log-logisticcumulative distribution function. Bubbles in the present system are plotted in the grace diagram,indicating that the bubbles cover both the spherical and ellipsoidal shape regimes. A generic empiricalcorrelation is proposed for the Sauter mean bubble diameter and distribution function parameters interms of operating conditions and physical properties of the system. Experimental data and correlationsfrom the literature and this study were compared with the results of the proposed correlation.

Experimental studies of bubble cutting in a lab-scale micro-structured bubble column with different liquid viscosity

Guanghui Chen,Zhongcheng Zhang,Fei Gao,Jianlong Li,Jipeng Dong 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.8

Bubble cutting was realized by installing a wire mesh in a micro-structured bubble column (MSBC) andstudied experimentally with liquid viscosity range from 1 to 39.6mPa·s. A non-intrusive high-speed camera methodwas used to determine bubble size and size distribution. The changes of gas holdup, bubble size, size distribution andSauter mean diameter before and after cutting were systematically studied with mesh openings of 3.8mm and 5.5mm. Three novel bubble cutting behaviors with uniform cutting, detachment cutting and indirect cutting behavior wereobserved. In the presence of two wire meshes, the bubble size distribution roughly shows a Gaussian curve distributionand the peak tends to shift towards lower diameters. With increasing liquid viscosity and superficial gas velocity,the dominant peak tends to move towards higher diameters, resulting in poor mesh cutting effect. After cutting, in thecase of two wire meshes, the Sauter mean diameter decreased by 33.5% and 22.2% and the gas holdup increased by3.2-12.2% and 1.2-4.4%, respectively. For the case of 3.8 mm mesh opening, the interfacial area increased by 10-26%,which is much better than 5.5mm mesh. The mean bubble size above the mesh will grow again and its growth ratedepends on the liquid viscosity.

음향 역산법을 이용한 기포의 크기 분포 추정 연구

박철수,정소원,김건도,문일성,임근태 한국음향학회 2020 韓國音響學會誌 Vol.39 No.3

This paper presents an acoustic inversion method for estimating the bubble size distribution. The estimation error of the attenuation coefficient represented by a Fredholm integral equation of the first kind is defined as an objective function, and an optimal solution is found by applying the Levenberg-Marquardt (LM) method. In order to validate the effectiveness of the inversion method, numerical simulations using two types of bubble distribution are performed. In addition, a series of experiments are carried out in a water tank (1.0 m × 0.54 m × 0.6 m), using bubbles generated by three different generators. Images of the distributed bubbles are obtained by a high-speed camera, and the insertion losses of the bubble layer are measured using a source and a hydrophone. The image is post-processed to glance a distribution characteristics of each bubble generator. Finally, the size distribution of bubbles is estimated by applying the inversion method to the measured insertion loss. From the inversion results, it was observed that the number of bubbles increases exponentially as the bubble size decreases, and then increases again after the local peak at 70 μm - 120 μm. 본 논문에서는 음향 역산법을 이용한 기포의 크기 분포 추정 기법을 제시하였다. 제 1종 Fredholm 적분방정식 으로 표현된 감쇠계수의 추정오차를 목적함수로 정의하였고, 최적해를 구하기 위해 Levenberg-Marquardt(LM)기법 을 적용하였다. 두 가지의 기포 분포에 대한 수치 시뮬레이션을 통해 제안된 역산 기법의 유용성을 검증하였다. 세 종류 의 기포발생기를 이용하여 사각 수조(1.0 m × 0.54 m × 0.6 m)에서 기포 실험을 수행하였다. 고속카메라 촬영을 통해 기포의 분포 이미지를 획득하였고, 음원과 수중청음기를 이용하여 기포층의 주파수별 삽입손실(insertion loss)을 계 측하였다. 촬영된 이미지는 후처리를 통해 기포 발생기별 기포 분포 특성을 파악하는데 활용하였고, 계측된 삽입손실 에 역산 기법을 적용하여 기포의 크기 분포를 추정하였다. 음향 역산결과로부터 기포의 크기가 작아짐에 따라 기포 개 수는 지수적으로 증가하며, 70 μm ~ 120 μm의 국부 피크를 지난 후 다시 증가하는 경향성을 확인하였다.

공기유입구를 가진 벤츄리 형상의 기포발생기에서 토출되는 기포 유동 특성의 가시화 측정 분석

배현우(Hyunwoo Bae),이승민(Seungmin Lee),송문수(Moonsoo Song),성재용(Jaeyong Sung) 한국가시화정보학회 2019 한국가시화정보학회지 Vol.17 No.1

Flow visualizations have been carried out to analyze the characteristics of bubby flows exhausted from a venturi-type bubble generator with an air vent. For various design parameters and operating conditions of the bubble generator, the images of bubbly flows was recorded using a high-speed camera and a microscope. Then the amount and size distribution of bubble was evaluated by an image processing technique. The results show that for increasing the amount of bubble, it is more effective to reduce the venturi throat than to enlarge the air vent diameter. If the water flow rate increases, the bubble generation rate increases but reaches a status of saturation, whose condition depends on Reynolds number at a given air vent diameter. The bubble size increases as the diameter of venturi throat decreases and Reynolds number increases. However, the air vent diameter is not a significant factor on bubble size.

Bubble size characteristics in the wake of ventilated hydrofoils with two aeration configurations

John S Gulliver,Ashish Karn,Christopher R Ellis,Christopher Milliren,Jiarong Hong,David Scott,Roger E.A. Arndt 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.2

Aerating hydroturbines have recently been proposed as an effective way to mitigate the problem of low dissolved oxygen in the discharge of hydroelectric power plants. The design of such a hydroturbine requires a precise understanding of the dependence of the generated bubble size distribution upon the operating conditions (viz. liquid velocity, air ventilation rate, hydrofoil configuration, etc.) and the consequent rise in dissolved oxygen in the downstream water. The purpose of the current research is to investigate the effect of location of air injection on the resulting bubble size distribution, thus leading to a quantitative analysis of aeration statistics and capabilities for two turbine blade hydrofoil designs. The two blade designs differed in their location of air injection. Extensive sets of experiments were conducted by varying the liquid velocity, aeration rate and the hydrofoil angle of attack, to characterize the resulting bubble size distribution. Using a shadow imaging technique to capture the bubble images in the wake and an in-house developed image analysis algorithm, it was found that the hydrofoil with leading edge ventilation produced smaller size bubbles as compared to the hydrofoil being ventilated at the trailing edge.

Bubble size characteristics in the wake of ventilated hydrofoils with two aeration configurations

Karn, Ashish,Ellis, Christopher R,Milliren, Christopher,Hong, Jiarong,Scott, David,Arndt, Roger EA,Gulliver, John S Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.2

Aerating hydroturbines have recently been proposed as an effective way to mitigate the problem of low dissolved oxygen in the discharge of hydroelectric power plants. The design of such a hydroturbine requires a precise understanding of the dependence of the generated bubble size distribution upon the operating conditions (viz. liquid velocity, air ventilation rate, hydrofoil configuration, etc.) and the consequent rise in dissolved oxygen in the downstream water. The purpose of the current research is to investigate the effect of location of air injection on the resulting bubble size distribution, thus leading to a quantitative analysis of aeration statistics and capabilities for two turbine blade hydrofoil designs. The two blade designs differed in their location of air injection. Extensive sets of experiments were conducted by varying the liquid velocity, aeration rate and the hydrofoil angle of attack, to characterize the resulting bubble size distribution. Using a shadow imaging technique to capture the bubble images in the wake and an in-house developed image analysis algorithm, it was found that the hydrofoil with leading edge ventilation produced smaller size bubbles as compared to the hydrofoil being ventilated at the trailing edge.

역전사 음향 산란장을 이용한 마이크로 기포 크기 분포 측정

오영주(Yeong Ju Oh),조대근(Dae Kun Cho),이경황(Kyoung Hwang Lee),이재영(Jae Young Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

A method to determine the size distribution of discrete bubbles in the bubbly flow is developed. From the scattered acoustic waves in the bubbly flow generates the dispersion relation which is the function of the number of the bubbles in the specific bubble size range, the sensitivity matrix was obtained. Several inverse algorithms were developed for the determination of the bubble size distribution. For the actualization, the excitation and sensing electronics were designed. It was found out that the present method is very sensitive to determine the Gaussian distribution of the bubble size and even it can predicts the existence of the cap bubbles in the discrete media.

원형 실린더 주위를 흐르는 기포류 유동의 기포 크기 영향에 대한 실험 연구

이주범(Jubeom Lee),박형민(Hyungmin Park) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

Two-phase cross flow over a bluff body occurs in many thermal and power systems such as steam generators, heat exchangers and nuclear reactors. However, only a few studies have been studied on the fundamental effects of the bubbles around the bluff body. Since the rising bubbles generate intensive liquid agitation, the resultant flow structures and bubble accumulation around the solid body are important to understand the pure bubble effect on flow field. In the present study, the two-phase flow phenomena around a smooth circular cylinder induced by the bubble column in a static water is experimentally investigated while varying the mean bubble sizes from 2 to 4 ㎜ and the void fraction by controlling the spargers separately. For the measurements, we basically use the shadowgraph technique and several image processing algorithms. In the wake behind a circular cylinder, the void distribution shows a specific trend similar to the formation of recirculation region for the single-phase flow, which changes with the mean void fraction and the bubble size. We will analyze this in terms of bubble dynamics and bubble-induced flows on a solid body.

Assessment of Acoustic Iterative Inverse Method for Bubble Sizing to Experimental Data

Choi, Bok-Kyoung,Kim, Bong-Chae,Kim, Byoung-Nam,Yoon, Suk-Wang The Korean Society of Oceanography 2006 Ocean science journal Vol.41 No.4

Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water. Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125-130 (2001)] reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation. It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing in the ocean.

Preliminary analyses on decontamination factors during pool scrubbing with bubble size distributions obtained from EPRI experiments

Lee, Yoonhee,Cho, Yong Jin,Ryu, Inchul Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.2

In this paper, from a review of the size distribution of the bubbles during pool scrubbing obtained from experiments by EPRI, we apply the bubble size distributions to analyses on the decontamination factors of pool scrubbing via I-COSTA (In-Containment Source Term Analysis). We perform sensitivity studies of the bubble size on the various mechanisms of deposition of aerosol particles in pool scrubbing. We also perform sensitivity studies on the size distributions of the bubbles depending on the diameters at the nozzle exit, the molecular weights of non-condensable gases in the carrier gases, and the steam fractions of the carrier gases. We then perform analyses of LACE-ESPANA experiments and compare the numerical ~ results to those from SPARC-90 and experimental results in order to show the effect of the bubble size distributions.