Visualized measurement of extremely high-speed droplets in Venturi scrubber

Venturi scrubbers for filtered venting have been installed in nuclear power plants worldwide. Venturi scrubbers can eliminate fission products from a polluted gas by interaction through gas–liquid interfaces. Therefore, droplet diameter is important from the viewpoint of decontamination. When Venturi scrubbers are used in severe accidents, the gas flow velocity might be extremely high. In these studies, the authors did not measure droplet diameter under extremely high gas velocity conditions. In the scenarios, experimental data pertaining to droplet diameter, under the extremely high gas flow velocity, are required. Therefore, this objective is to evaluate the diameter of extremely high-speed droplets. A visualization experiment was conducted using a Venturi scrubber. The droplet diameter distribution and the Sauter mean diameter (SMD) were determined. By comparing between the experimental value of SMDs and the one evaluated using Nukiyama–Tanasawa equation, it was confirmed that the Nukiyama–Tanasawa equation can be used to evaluate SMD with good accuracy in the gas velocity range of 82–250 m/s, except the highest gas velocity conditions. Furthermore, the droplet generation mechanism in the Venturi scrubber was considered to clarify the main reason why the Nukiyama–Tanasawa equation can be used to evaluate SMD droplet diameter.     

Droplets Manipulated on Photothermal Organogel Surfaces

A photoresponsive organogel surface (POS), which integrates characteristics of the photothermal property of Fe₃O₄ nanoparticles and the low hysteresis feature of lubricant‐infused organogels, is shown. A photothermally induced dynamic temperature gradient can be formed rapidly at the location of near‐infrared‐light irradiation (NIR) on POS with suitable Fe₃O₄ nanoparticles content. Thus, various droplets (e.g., water, glycerol, ethylene glycol, propylene glycol, and ethanol) can be transported effectively and nimbly (e.g., along desired trajectories with controllable velocity and direction, even run uphill and deliver solid particles). This work reveals a synergistic effect between the asymmetrical droplet deformation and the inside Marangoni flows, which forms a unique driving force for droplet transport with high efficiency. This finding offers insight into the design of novel responsive interface materials for droplet transportation, which would be significant for laboratory‐on‐a‐chip contexts, mass transportation, and microengines.     

A microfluidic toolbox for cell fusion

Cellular fusion is a key process in many fields ranging from historical gene mapping studies and monoclonal antibody production, through to cell reprogramming. Traditional methodologies for cell fusion rely on the random pairing of different cell types and generally result in low and variable fusion efficiencies. These approaches become particularly limiting where substantial numbers of bespoke one‐to‐one fusions are required, for example, for in‐depth studies of nuclear reprogramming mechanisms. In recent years, microfluidic technologies have proven valuable in creating platforms where the manipulation of single cells is highly efficient, rapid and controllable. These technologies also allow the integration of different experimental steps and characterisation processes into a single platform. Although the application of microfluidic methodologies to cell fusion studies is promising, current technologies that rely on static trapping are limited both in terms of the overall number of fused cells produced and their experimental accessibility. Here we review some of the most exciting breakthroughs in core microfluidic technologies that will allow the creation of integrated platforms for controlled cell fusion at high throughput. © 2015 Society of Chemical Industry     

AP1000次级汽水分离器分离性能及结构优化的数值研究

建立AP1000次级波纹板汽水分离器内两相流动的数学模型,随后数值模拟波纹板内的两相流动,并分析其分离性能。进而对波纹板结构进行优化,得到具有较高分离效率和较低流动阻力的新型波纹板。首先分别建立波纹板内部蒸汽相和液滴相运动的数学模型。然后通过自编程序与Fluent软件耦合对该两相流动模型数值求解。随后得到波纹板进出口总压降,并通过模拟液滴在波纹板内的运动轨迹,得到波纹板的分离效率和内部液滴湿度分布。进而以分离效率和流动压降为目标优化波纹板结构,设计得到具有较高分离效率和较低流动阻力的新型波纹板。本文提出的数值模拟方法对汽水分离器结构的设计和优化具有较强的指导意义。     

Electro-coalescence of an aqueous droplet at an oil-water interface

The coalescence of an aqueous droplet at an oil-water interface under an electric field has been investigated, with a view to quantify conditions that give rise to secondary droplet formation. Two patterns of drop-interface coalescence may occur: complete coalescence and partial coalescence. The former is obviously the desirable pattern for industrial coalescers. However in practice, the process of coalescence could actually produce smaller droplets, which become more difficult to remove, and hence undesirable. This is caused by either necking, due to extensive elongation of the droplet, or reaction to a fast and energetic coalescence and is referred to as partial coalescence. The volume of the droplets formed in this way has been analyzed as a function of the initial droplet size, electric field strength and the distance between the droplet and the interface. The expansion speed of the neck connecting the droplet and interface at the beginning of the pumping process has also been quantified. These results are useful in optimizing the electro-coalescence process.     

NIR驱动MWCNT修饰的超滑PI光热响应膜表面液滴定向输运

目的 制备多壁碳纳米管(MWCNT)修饰的超滑聚酰亚胺(PI)光热响应膜表面,实现近红外光(NIR)驱动液滴定向输运.方法 基于静电纺丝结合喷涂法制备MWCNT修饰的超滑PI光热响应膜表面,分别通过扫描电子显微镜、接触角测量仪、红外热成像仪表征样品的微观形貌、润湿特性及光热特性,分析液滴大小与润滑油黏度对液滴定向输运的影响规律,研究NIR驱动液滴在MWCNT修饰的超滑PI光热响应膜表面定向输运的作用机理.结果 MWCNT修饰PI膜表面的疏水性提高,液滴静态接触角从115°增大至160°.NIR连续照射MWCNT修饰的超滑PI光热响应膜表面90 s,表面温度的最大上升速率为42.6℃/s,表面最大温度达到123.6℃.通过NIR照射超滑PI纳米纤维膜表面,表面局部温度上升,产生润湿梯度力,驱动液滴在表面定向输运.液滴定向输运与润湿梯度力及粘滞阻力有关.超滑PI光热响应膜表面的润滑油黏度相同时,液滴体积越小,粘滞阻力越小,液滴定向输运的速度越快.5μL液滴在润滑油黏度为0.65 mm2/s的超滑PI光热响应膜表面的运动速度最大,运动速度为1.64 mm/s.液滴体积相同时,超滑PI光热响应膜表面的润滑油黏度越大,液滴受到的润湿梯度力越小.5μL液滴在润滑油黏度为100 mm2/s的超滑PI光热响应膜表面的润湿梯度力Fwet-grad最小,润湿梯度力为6.39×10?6 N.结论 MWCNT修饰的超滑PI光热响应膜表面具有良好的光热效应,NIR可精准驱动单液滴及多液滴在表面的定向输运.     

复合绝缘子弱憎水性状态描述方法Ⅲ——液滴面积法的适用性

寻求合适的方法及参数来描述染污复合绝缘子的弱憎水性状态,对弱憎水性状态给出明确的定义,并对当前已有的7个憎水等级进一步细化。通过10μL靛蓝溶液在染污高温硫化硅橡胶试片表面的垂直投影面积,来反映污层的憎水性状况,并尝试将液滴面积与染污绝缘芯棒的污闪电压建立联系,以揭示弱憎水性阶段憎水性能改变对绝缘子污闪特性的影响。结合液滴在污层表面的形态以及试品的污闪特性,在人工污秽试验的基础上将当前憎水等级HC7进一步细化为四个阶段,分别是HC7A、HC7B、HC7C及HC7D。比较液滴面积、液滴接触角以及喷水分级试验结果,将新憎水等级HC7B定义为弱憎水性状态。试验研究认为:液滴面积法弥补了液滴接触角法在染污试品呈弱憎水性状态下的不足,可以用于弱憎水性阶段的憎水特性研究;而憎水性较强时,面积法对憎水性的辨识能力有限,选用接触角法更适合此阶段的研究。