Mathematical Analysis of Unsteady MHD Blood Flow through Parallel Plate Channel with Heat Source

In the present study, a mathematical model of unsteady blood flow through parallel plate channel under the action of an applied constant transverse magnetic field is proposed. The model is subjected to heat source. Analytical expressions are obtained by choosing the axial velocity;temperature distribution and the normal velocity of the blood depend on y and t only to convert the system of partial differential equations into system of ordinary differential equations under the conditions defined in our model. The model has been analyzed to find the effects of various parameters such as, Hartmann number, heat source parameter and Prandtl number on the axial velocity, temperature distribution and the normal velocity. The numerical solutions of axial velocity, temperature distributions and normal velocity are shown graphically for better understanding of the problem. Hence, the present mathematical model gives a simple form of axial velocity, temperature distribution and normal velocity of the blood flow so that it will help not only people working in the field of Physiological fluid dynamics but also to the medical practitioners.

Run-Up Flow of a Maxwell Fluid through a Parallel Plate Channel

We consider the flow of an incompressible viscous Maxwell fluid between two parallel plates, initially induced by a constant pressure gradient. The pressure gradient is withdrawn and the upper plate moves with a uniform velocity while the lower plate continues to be at rest. The arising flow is referred to as run-up flow. The unsteady governing equations are solved as initial value problem using Laplace transform technique. The expression for velocity, shear stresses on both plates and discharge are obtained. The behavior of the velocity, shear stresses and mass flux has been discussed in detail with respect to variations in different governing flow parameters and is presented through graphs.

Hall Current Effects on Unsteady MHD Flow in a Rotating Parallel Plate Channel Bound-ed by Porous Bed on the Lower Half—Darcy Lapwood Model

We discussed the unsteady flow of an incompressible viscous fluid in a rotating parallel plate channel bounded on one side by a porous bed under the influence of a uniform transverse magnetic field taking hall current into account. The perturbations are created by a constant pressure gradient along the plates in addition to the non-torsional oscillations of the upper plate. The flow in the clean fluid region is governed by Navier-Stoke’s equations while in the porous bed the equations are based on Darcy-Lapwood model. The exact solutions of velocity in the clean fluid and the porous medium consist of steady state and transient state. The time required for the transient state to decay is evaluated in detail and ultimate quasi-steady state solution has been derived analytically and also its behaviour is computationally discussed with reference to different flow parameters. The shear stresses on the boundaries and the mass flux are also obtained analytically and their behaviour is computationally discussed.

Hall Effects on Unsteady MHD Three Dimensional Flow through a Porous Medium in a Rotating Parallel Plate Channel with Effect of Inclined Magnetic Field

In this paper, we make an initial value investigation of the unsteady flow of incompressible viscous fluid between two rigid non-conducting rotating parallel plates bounded by a porous medium under the influence of a uniform magnetic field of strength H0 inclined at an angle of inclination α with normal to the boundaries taking hall current into account. The perturbations are created by a constant pressure gradient along the plates in addition to the non-torsional oscillations of the upper plate while the lower plate is at rest. The flow in the porous medium is governed by the Brinkman’s equations. The exact solution of the velocity in the porous medium consists of steady state and transient state. The time required for the transient state to decay is evaluated in detail and the ultimate quasi-steady state solution has been derived analytically. Its behaviour is computationally discussed with reference to the various governing parameters. The shear stresses on the boundaries are also obtained analytically and their behaviour is computationally discussed.

Forced Convective Heat Transfer in a Porous Plate Channel

Forced convective heat transfer in a plate channel filled with metallic spherical particles was investigated experimentally and numerically. The test section, 58 mm×80mm×5mm in size, was heated by a 0.4 mm thick plate electrical heater. The coolant water now rate ranged from 0.015 to 0.833 kg/s.The local wall temperature distribution was measured along with the inlet and outlet fluid temperatures and pressures. The results illustrate the heat transfer augmentation and increased pressure drop caused by the porous medium. The heat transfer coefficient was increased 5-12 times by the porous media although the hydraulic resistance was increased even more. The Nusselt number and the heat transfer coefficient increased with decreasing particIe diameter, while the pressure drop decreased as the particle diameter increased. It was found that, for the conditions studied (metallic packed bed),the effect of thermal dispersion did not need to be considered in the physical model, as opposed to a non-metallic packed bed, where thermal dispersion is important.

Experiment investigation on visualization and operating characteristics of closed loop plate oscillating heat pipe with parallel channels

Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying liquid filled ratios(50%, 70%, 85%), section scales(1 mm×1 mm and 1 mm×1.5 mm), inclination angles, working fluids and heating inputs. It was found that during operating there was mixed flow consisting of plug flow and annular flow in channels of oscillating heat pipe at steady-state. There was an equilibrium position for working fluid of condenser during oscillating, and periodic oscillations occurred up and down in the vicinity of equilibrium position. With heat input increasing, equilibrium position rose slowly as a result of vapor pressure of evaporation.Evaporation temperature oscillating amplitude possessed a trend of small-large-small and frequency trend was of small-large during steady-state. It may be generally concluded that temperature, whether evaporator or condenser, fluctuated sharply or rose continuously when oscillating heat pipe coming to dry burning state. Simultaneously, it was found that temperature difference of cooling water possibly dropped with heat input rising during dry burning state. Thermal resistance of No. 2 with acetone was lower than that of No. 1 during experiments, but No. 2 achieving heat transfer limit was earlier than No. 1. However, with ethanol, thermal resistance of No. 1 and No. 2 were similar with the heating input less than 110-120 W and filling ratios of 50% and 70%. And with filling ratio of 85%, heating transfer performance of No. 2 was better compared to No. 1 during all the experiments.

Fabrication of micro-flow channels on graphite composite bipolar plates using microplaning

A new method of manufacturing micro-flow channels on graphite composite bipolar plate(GCBPP) microplaning using specially designed multi-tooth tool is proposed. In this method, several or even dozens of parallel micro-flow channels ranging from 100 μm to 500 μm in width can be produced simultaneously. But, edge chippings easily occur on the rib surface of GCBPP during microplaning due to brittleness of graphite composites. Experimental results show that edge chippings result in the increase of contact resistance between bipolar plate and carbon paper at low compaction force. While the edge chippings scarcely exert influence on the contact resistance at high compaction force. Contrary to conventional view, the edge chippings can significantly improve performance of microfuel cell and big edge chippings outperform small edge chippings. In addition, the influence of technical parameters on edge chippings was investigated in order to obtain big, but not oversized edge chippings.

航空锂电池焊缝的多通道多频涡流检测

为了实现航空锂电池极耳极板激光焊缝的高效准确检测,设计制作了带有层析成像功能的多通道多频涡流检测系统.采用该系统及5通道防干扰差分结构涡流传感器对极耳极板焊缝中的局部断焊、整体漏焊、焊缝变形内凹、微小缺陷等典型缺陷进行检测,并基于趋肤效应原理,采用层析成像技术对焊瘤缺陷进行扫查成像.结果表明,研发的带有层析成像功能的多通道多频涡流检测系统可有效检测出锂电池极耳极板焊缝中的多种典型缺陷,最小可检测1 mm的缺陷,层析成像技术可实现不同深度下缺陷的形貌观测.通过对大量检测结果的对比分析,总结了缺陷种类、位置及长度的判别方法,提出了一套缺陷判别流程与评定准则,为实现锂电池极耳极板焊缝检测的工程化奠定了良好的基础.

全钒液流电池双极板材料研究进展

全钒液流电池是目前技术成熟度最高的一种液流电池,作为大规模长时储能的首选技术之一,可以实现可再生能源平滑输出,为高比例可再生能源并网应用提供保障。其中,双极板是全钒液流电池的关键部件之一。本文从三种全钒液流电池双极板材料耐腐蚀性、导电性、力学性能及电池特性等角度,首先综述了金属、石墨以及碳塑复合双极板材料的优缺点及其最新研究进展,并根据加工工艺和制造成本两方面,展望了三种双极板材料在全钒液流电池领域的应用前景。然后,结合新型液流电池双极板的结构优化研究,从双极板平板结构扩展到双极板流道和电极-双极板一体化结构,分析介绍了不同新型双极板流道结构设计在不同试验条件下的适用性,并从制备工艺和电池性能等方面分析了电极-双极板一体化结构在全钒液流电池领域中的应用前景。最后,针对全钒液流电池双极板的研究现状,总结展望了相应双极板材料及新型双极板结构设计的技术突破要点,为全钒液流电池双极板的未来发展提供了参考和依据。

混合动力机车电池组液冷板流道结构选型研究

为了选出混合动力机车电池组液冷板的最优流道结构,文章结合电池组液冷原理提出了4种流道结构模型,并在环境温度35℃、冷却液进口速度2 L/min和进口温度25℃的条件下,进行热仿真分析。通过对比分析发现,随着并行流道数量的增加,电池组的平均温度、最高温度、最大温差均呈上升趋势,冷却液的进出口压差均呈下降趋势。综合评价指标及冷却液流速情况,两并行流道被确定为该电池组最适配的液冷板流道结构。

基于多目标粒子群优化算法的动力电池仿生冷板结构优化设计

为了提高锂离子电池的冷却效果,提出一种高度对称的仿生网状流道冷板。首先,利用单因子分析法分析了冷板结构参数对其性能的影响,然后,以冷板的平均温度、温度标准差和冷却液压力损失为性能指标,采用多目标粒子群优化(MOPSO)算法对冷板的结构参数进行了优化,得到性能最优时的流道宽度、流道深度和冷板壁厚分别为9.0 mm、1.5 mm和1.4 mm,对应的平均温度、温度标准差和压力损失分别为33.20℃、1.33℃和65.63 Pa,相比于初始结构参数,优化后的平均温度和温度标准差分别下降1.92℃和0.02℃,但压力损失增大27.10 Pa。最后,在电池模组层面验证了优化结果。

质子交换膜燃料电池金属双极板流道结构及制造工艺

金属双极板因具有强度高、导电性和传热能力好、能量损失小、密封性好等优势,且加工方便、加工成本低、可制造超薄厚度及高体积比功率等特性,逐渐成为双极板材料的首选,而流道结构设计和制造工艺是影响金属双极板成形质量和工作性能的关键。对比了金属双极板常用传统流道结构与新型流道结构,分析了结构变化对燃料电池性能的影响;梳理了金属双极板的冲压成形、液压成形、软膜成形、辊轧成形、电磁成形、特种成形等塑性成形工艺技术及成形装备;最后对金属双极板的流道结构设计与制造工艺进行了展望。

多结构形式小通道液冷板散热性能对比研究

小通道冷板作为一种有效的热控装置,已被广泛应用于高热流密度电子器件的热管理领域。文中以通道特征尺寸为2 mm的串行、并行以及射流冲击/小通道混合液冷板为研究对象,旨在获取这3种结构形式冷板的极限散热能力和流动阻力损失的差异。研究结果表明:在相同冷却工质流量条件下,3种冷板的散热功率由大到小依次为串行通道、射流冲击/小通道混合液冷板、并行通道;串行通道冷板的板内阻力损失明显大于其余两者;在综合考虑压力损失和散热性能的基础上,根据不同热源热流密度条件选择合适的冷板结构,有望满足特定应用的需求。该研究可供小通道液冷板的设计和优化参考。

基于图像处理的微通道流道板表面缺陷检测方法研究

针对工业自动化生产中微通道流道板复杂结构表面缺陷自动检测的需求,提出了一种基于图像处理的流道板表面缺陷检测方法。该方法针对流道板CV孔和膨胀阀孔中常见的凹坑缺陷和破损缺陷,首先通过霍夫圆检测提取ROI区域剔除背景区域干扰,利用高斯滤波对ROI图像进行滤波处理,并使用二值化和形态学腐蚀运算对干扰噪点进行过滤从而凸显缺陷特征,之后使用Two-Pass算法和种子填充法计算连通域实现凹坑缺陷的检测;使用圆查找找到孔端面内外圆进行圆环展开并采用Canny边缘检测算子查找缺陷轮廓,筛选轮廓面积实现破损缺陷的检测。通过对比实验,验证了本文方法相较于传统表面缺陷检测方法,在流道板缺陷样本的检测中有更高的检出率。本文方法经验证,对流道板表面缺陷检出率稳定在92%以上,且算法处理速度快、鲁棒性强,实现了快速、非接触式的高精度检测,满足了工业自动化需求。

微小通道冷板流动传热仿真校核方法研究

针对现有冷板流动传热仿真往往基于经验开展、缺乏对仿真模型严谨校核的问题,面向冷板流动传热仿真模型的两个重要方面,即离散网格与流动模型开展校核方法研究,一方面应用Richardson外推法对离散网格进行校核,另一方面通过将层流模型、SST k-ω、Transition k-ω以及RNG k-ε湍流模型与理论或经验关联式对比进行流动模型校核。结果表明,Richardson外推法的可获得量化的离散误差评估,有助于冷板流动传热仿真的网格优化;应用关联式能较简单地评估不同流动模型在不同条件下的适用性,同时发现Transition SST或SST k-ω在总体适用性较好。

吸油烟机油烟过滤通道的滤油特性和气动性能研究

弯折分离板通道用于吸油烟机油烟过滤具有一定优势,但其滤油特性和气动性能仍未探明。基于空气动力学基本原理,对弯折分离板通道进行了重新设计,并采用计算流体力学方法和多相流模型研究了不同宽度通道的滤油特性和气动性能。结果表明,弯折通道对于较大颗粒的油脂过滤效果较好,但对于直径低于5μm的油脂颗粒捕获率不高;随着通道宽度的减小,油烟过滤效果进一步提升,但压降(流动阻力)先降低后增加。通过对通道添加压力平衡孔进行改进,有效提升了油烟过滤效果,但也导致了压降的增大。

基于改进薄板样条运动模型的人脸动画算法

面部动画在电影、游戏、虚拟现实等领域起着关键作用,对于实现逼真、生动的人脸动画和情感传达至关重要。当面临面部形状、姿态、表情等多个变化因素时,虽然通过薄板样条非线性变换可以获得较好的运动估计结果,但在处理面部复杂纹理和嘴部运动时存在运动估计不精细的问题,需要更强大的图像修复能力。因此,提出一种基于改进薄板样条运动模型(TPSMM)的人脸动画算法。首先,在TPSMM的基础上引入一种Farneback光流金字塔算法,通过与薄板样条变换和背景仿射变换相结合,使得人脸局部运动估计更精准;其次,为了更真实地恢复缺失区域的细节纹理信息,提出一种多尺度细节感知网络,该网络在编码器中通过嵌入通道注意力(ECA)模块减少源图像因多层下采样而导致的人脸细节信息丢失,在解码器中利用坐标注意力(CA)模块来有效捕获运动估计特征图中不同位置的重要特征,提高人脸图像的生成质量。实验结果表明,相比一阶段运动模型(FOMM)、关节动画的运动表示法(MRAA)、TPSMM等,该算法在MUG、UvA-Nemo和Oulu-CASIA数据集上的L1、平均关键点距离(AKD)、平均欧氏距离(AED)数值均达到最优,平均分别为0.0129、0.923、0.00099。

某控制器液冷板仿真优化设计与评估

某发动机控制器中驱动板采用液冷散热技术,为此开展了液冷板的散热性能仿真优化设计与力学性能评估。首先基于液冷板外形结构提出一种S形流道结构设计方案,接着仿真验证了液冷板的散热性能,并基于仿真结果优化了流道结构。优化结果表明,液冷板上最大温差由10.41℃降为4.82℃,满足温差不大于5℃的设计要求,散热性能改善117%。进一步评估流体入口压力10 MPa工况下的液冷板力学性能,流-固耦合仿真得到的最大等效应力为71.59 MPa,远低于液冷板铝合金材料屈服强度255 MPa,力学结构可靠。

钢厂冲渣水余热回收供南方城市集中供暖方案论证

文章以汉中市勉县作为南方非集中供暖区域典型县市,利用陕钢高炉冲渣水的余热作为集中供暖热源,通过对比分析两种不同的余热回收方式,论证了冲渣水余热作为南方城市集中供暖基础热源的技术可行性与经济性。结果表明,直热机余热回收方式虽然能保证供热的稳定性与持续性,但显著增加了换热首站的建设成本和供暖期间的运营成本;宽流道板换便于安装,设备占地面积小,通过进行定期清理与设备保养,能够做到供暖期间稳定运行。因此,针对技改项目、建设用地受限等情况,建议采用宽流道板换方案。

一种基于通道注意力机制的交通监控视频超分辨率算法

为提升交通监控视频的显示质量,进而提高监控视频车牌识别成功率,提出一种基于通道注意力机制(Channel-wise Attention,CA)和BasicVSR模型的监控视频超分辨率模型。在BasicVSR模型中引入CA,使模型能学习不同通道之间的非线性依赖关系,从而有效提升监控视频超分辨率图像的质量。在某交通监控场景下开展车牌识别试验,对该CA-BasicVSR模型的有效性进行验证,结果表明:在交通监控画面还原任务中,该模型对画面还原的峰值信噪比相比EDVR-L模型和BasicVSR模型能分别提高约1.3 dB和0.3 dB;在车牌识别任务中,使用该模型处理的交通监控视频画面作为输入,相比原始低分辨率的视频画面,能提高车牌识别的成功率。