Nanofluidics

纳米流体
  • 文章类型: Journal Article
    本研究的主要目标是提出在新兴技术中增强传热的概念。为了实现这一点,将尺寸为1至100nm的微小金属和非金属颗粒引入基液中。这些纳米级颗粒用于改善液体的热性能,导致所谓的纳米流体。这些流体的利用和薄膜流动的检查在各个领域,如工程,技术,和工业。这项研究的重点是分析纳米流体的对流流动行为,具体来说,移动表面上的氧化石墨烯-乙二醇(GO-EG)和氧化石墨烯-水(GO-W)。该研究调查了磁场和变化粘度的影响。通过利用基础流体和纳米流体的热物理特性,以及在控制能量和动量的基本方程中实现相似性变换,我们制定了一个五阶非线性常微分方程(NODE)来描述速度分布。这与描述温度分布的二阶节点相结合。要解决此派生节点,我们采用一种称为同伦分析方法(HAM)的方法进行分析求解。相关因素的影响,普朗特号,包括磁场参数,液体的厚度,耦合应力参数,温度分布,动态粘度,和Eckert号码,在皮肤上摩擦,速度剖面,和Nusselt的号码通过图形表示进行询问。速度场表现出作为偶应力参数的下降,磁场参数,液体厚度,和动态粘度的经验增加。相反,随着Eckert数和动态粘度的增加,温度场显示出上升。为确保问题的衔接,采用了问题的双重解决方案,这通过利用率图和表进行了验证。由于在冷却汽车等行业的各种设备和设备的传热应用中遇到了相当大的挑战,微电子,防御,和制造业,人们强烈期望这种理论方法可以对提高传热效率做出有利的贡献。寻求这种改进以满足制造和工程部门的要求。
    The main goal of this research is to present the concept of enhancing heat transfer within emerging technology. To achieve this, tiny metal and nonmetal particles ranging from 1 to 100 nm in size are introduced into base liquids. These nanoscale particles are utilized to improve the thermal performance of the liquids, leading to what are termed nanofluids. The utilization of these fluids and the examination of the flow of thin films have valuable implications across various sectors such as engineering, technology, and industries. This research focuses on analyzing the convective flow behavior of nanofluids, specifically, graphene oxide-ethylene glycol (GO-EG) and graphene oxide-water (GO-W) on a moving surface. The study investigates the impacts of magnetic fields and varying viscosity. By making use of the thermophysical characteristics of the base fluid and the nanofluid, as well as implementing a similarity transformation within the fundamental equations that govern energy and momentum, we formulate a 5th order nonlinear ordinary differential equation (NODE) to describe the velocity profile. This is combined with a second-order NODE that describes the distribution of temperature. To solve this derived NODE, we employ a method known as the Homotopy Analysis Method (HAM) for analytical solution. The impact of the relevant factors, Prandtl number, including magnetic field parameter, thickness of the liquid, couple stress parameter, temperature distribution, dynamic viscosity, and Eckert number, on the skin friction, velocity profile, and Nusselt\'s number are interrogated through graphical representation. The velocity field exhibits a decline as the couple stress parameter, magnetic field parameter, liquid thickness, and dynamic viscosity experience an increase. Conversely, the temperature field displays a rise as the Eckert number and dynamic viscosity experience an increase. To ensure the convergence of the issue, dual solutions of the problem are employed, and this is verified through the utilization graphs and tables. Due to the considerable challenge encountered in heat transfer applications for cooling diverse equipment and devices across industries like automotive, microelectronics, defense, and manufacturing, there is a strong expectation that this theoretical methodology could make a favorable contribution towards enhancing heat transfer efficiency. This improvement is sought to meet the requirements of the manufacturing and engineering sectors.
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  • 文章类型: Journal Article
    使用阴离子交换膜(AEM)和阳离子交换膜(CEM)的电渗析已广泛用于水脱盐和各种离子物质的管理。在商业电渗析期间,离子交换膜的可用面积通过与AEM/CEM接触的非导电间隔件而减小。尽管有多个报告描述了垫片的优点或缺点,较少研究探索隔片对减少膜面积不包括流体流量变化的传质效应的影响。在本文中,我们介绍了有关具有部分掩蔽的离子交换膜的微流体电渗析系统中质量传输的实验研究。通过在部分膜上沉积非导电膜来制备六种不同类型的掩蔽膜。实验结果表明,重叠类型(其中掩模在AEM/CEM中垂直对齐)表现出更大的电导率和更好的电流/能量效率,与非重叠类型(其中掩蔽在AEM/CEM中垂直错位)相比。我们还观察到,未掩盖的离子交换膜的单位长度减少会增强整体质量传输。我们的结果证明了图案化膜对电阻和脱盐性能的影响;它们还确定了用于电隔膜系统的适当布置。
    Electrodialysis using anion-exchange membranes (AEMs) and cation-exchange membranes (CEMs) has been widely used for water desalination and the management of various ionic species. During commercial electrodialysis, the available area of an ion-exchange membrane is reduced by a non-conductive spacer that is in contact with the AEM/CEM. Although multiple reports have described the advantages or disadvantages of spacers, fewer studies have explored the effects of spacers on the mass transport effect of the reduced membrane area excluding the fluid flow change. In this paper, we present our experimental studies concerning mass transport in microfluidic electrodialysis systems with partially masked ion-exchange membranes. Six different types of masking membranes were prepared by the deposition of non-conductive films on parts of the membranes. The experimental results showed that the overlapped types (in which masking was vertically aligned in the AEM/CEM) exhibited a larger electrical conductance and better current/energy efficiency, compared with the non-overlapped types (in which masking was vertically dislocated in the AEM/CEM). We also observed that a reduction in the unit length of the unmasked ion-exchange membrane enhanced overall mass transport. Our results demonstrate the effects of patterned membranes on electrical resistance and desalination performance; they also identify appropriate arrangements for electromembrane systems.
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  • 文章类型: Journal Article
    本工作的主要目的是探索MWCNT在水-太阳能乙二醇(70:30)混合物中的分散对其电导率和热物理性质如密度的影响,流变性和导热性。通过常见的两阶段合成技术以0.15、0.3和0.45的各种重量百分比接种MWCNT。通过高分辨率扫描电子显微镜和紫外-可见光谱证实了MWCNTs基纳米流体的均匀稳定性。基于太阳能乙二醇和H2O混合物的MWCNT纳米流体的密度是通过称重平衡机制用标准硼硅容量瓶测量的,实验结果显示与Pak和Cho的众所周知的相关性具有良好的一致性,这是由于H2O在有限的量内的天然填料。0.45wt。%MWCNT在环境温度下接种增加了19.12%,而电导率在50°C下增加了93.54%。因此,水/太阳能乙二醇混合物的热导率增加了0.45wt。%MWCNT引晶是由于纳米材料积累和流体分层的动力学。此外,建议使用数学相关性来估计不同重量分数下纳米流体的热导率和粘度之比。
    The main aim of this present work is to explore the influence of dispersion of MWCNTs in a mixture of water-solar glycol (70:30) on its electrical conductivity and thermophysical properties such as density, rheology and thermal conductivity. The MWCNTs were seeded with a various weight percentage of 0.15, 0.3 and 0.45 via a common two-stage synthesis technique. The homogeneous stability of MWCNTs based nanofluids was confirmed by high-resolution scanning electron microscopy and ultraviolet-visible spectroscopy. The density of solar glycol and H2O mixture based MWCNTs nanofluids were measured with standard borosil volumetric flask via weighing balance mechanism and the experimental findings displayed a good agreement with the well-known correlation of Pak and Cho owing to the natural packing of H2O inside the nanomaterial in a limited quantity. The thermal conductivity of 0.45 wt. % MWCNTs seeding got augmented by 19.12% at ambient temperature while the electrical conductivity got augmented by 93.54% at 50 °C. Therefore, the augmentation in the thermal conductivity of water/solar glycol mixture with 0.45 wt. % MWCNTs seeding is because of the kinetics of nanomaterial accumulation and fluid layering. In addition, mathematical correlations were recommended for estimating the ratio of the thermal conductivity and viscosity of the nanofluid at different weight fractions.
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