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Chemical vapor deposition of TiN on a spherical particle surface subjected to nanosecond laser heating is simulated numerically here. A thermal model is developed to describe the heat transfer within the particle, chemical reaction on the particle surface, and mass transfer in the gases. The heat conduction and mass diffusion equations are discretized using the finite volume method with fully implicit schemes, and solved with tridiagonal matrix method. Temporal distributions of particle surface temperature and deposited film thickness resulting from multiple-pulse irradiation are analyzed for a wide range of parameters including laser fluence, pulse repetition frequency, pulse width, initial particle temperature, particle radius, and total pressure in the reaction chamber. 相似文献
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S. Ya Misyura 《Nanoscale and Microscale Thermophysical Engineering》2018,22(3):213-229
Heat transfer of a droplet and layer during evaporation of aqueous solutions of salts has been studied. The behavior of salt solutions on a smooth and microstructured surface is compared here. Evaporation rate of aqueous salt solutions is greater for a microstructured surface than for a smooth wall. The behavior of heat transfer coefficient α can be described by two time regimes: quasi-constant values of α and significant increase in heat transfer at a multiple decrease in the liquid layer height. Measurements made with application of the particle image velocimetry showed that the structured surface increases liquid speed inside the sessile drop. The largest value of the heat transfer coefficient α on the structured surface corresponds to water for the final stage of evaporation. For salt solutions, the heat transfer coefficient is lower than that for water in the entire period of evaporation on the structured surface. The maximal excess (20–30%) of α of the structured wall above the smooth surface corresponds to the maximal height of the liquid layer at the beginning of evaporation. With increasing time, the excess is reduced. A drop of heat transfer intensification with a decrease in the layer height relates to suppression of free convection (a multiple decrease in the average velocity in the drop). 相似文献
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应用数值模拟方法研究单液滴撞击薄液膜的动力学行为.在二维轴对称坐标系内,采用VOF方法与网格局部瞬时加密技术相结合,跟踪液滴和液膜与空气间的气液两相界面.结果表明,液滴撞击薄液膜的演化行为主要受液滴初始动能、表面张力以及液体黏性的影响.初始动能越大,则形成的空间液膜最大高度越大,达到稳定状态越晚,飞溅开始时刻越早,飞溅生成的二次液滴数量也越多;在扩展后期及回缩阶段,空间液膜的形成主要受液体黏度影响,增加液体黏度会阻碍空间液膜飞溅;表面张力增大,形成的空间液膜高度减小、厚度增加,同时阻碍二次液滴的生成. 相似文献
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基于格子玻尔兹曼方法(Lattice Boltzmann Method, LBM)对固着在加热基板上的液滴铺展及蒸发过程进行模拟,主要研究重力场、基板润湿性以及初始环境温度对液滴铺展及蒸发过程的影响。通过预测蒸发过程中液滴与基板的接触直径变化和液滴剩余质量变化,分析液滴形状及体积变化。研究结果发现,液滴形貌及蒸发过程受重力影响较大,重力作用下液滴铺展现象明显且蒸发加快。基板的接触角越小,液滴铺展现象越明显,其接触直径越大,蒸发越快。当环境温度与基板温度相差较大时,液滴内部出现涡流,强化换热使蒸发过程加快。 相似文献
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摘要: 太阳能电池板表面灰尘颗粒的沉积严重制约着光伏发电效率,降低了电池板的使用寿命。提出建立灰尘与电池板间耦合关系以及计算清除灰尘作用力的方法;提出3条接触模型等价性假设,并基于离散元与弹塑性理论建立灰尘颗粒与电池板及灰尘颗粒间的力学模型;利用EDEM软件的Hertz-Mindlin with JKR Cohesion模型,仿真模拟电池板表面灰尘分布情况,预测清洗电池板的清洗力大小及清洗区域;分析电池板倾角、风向与电池板和颗粒间作用合力即清洗力的对应关系;为所研制电池板表面积灰清除机器人的清洗力和清洗周期确定提供理论依据。 相似文献
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Hoa D. Nguyen Seungho Paik Jacob N. Chung 《Numerical Heat Transfer, Part A: Applications》2013,63(2):161-180
Thermal behavior of a liquid drop moving in an incompressible fluid of infinite extent is investigated numerically. Dynamical equations describing the temporal evolution of the flow and temperature fields of dispersed and continuous phases are solved by a hybrid spectral scheme in conjunction with the influence matrix technique to resolve the lack of vorticity boundary conditions. Both Chebyshev and Legendre polynomials are employed to expand the flow variables and temperature in the radial and angular directions, respectively. With the aid of the Galerkin and collocation methods, together with the first-order backward Euler time differencing, the governing partial differential equations reduce to a nonlinear system of algebraic equations. Numerical results reveal a discrepancy between quasi-steady and fully transient analyses at high Peclet numbers. 相似文献
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水平热壁上泄漏燃料蒸发与着火的数值模拟 总被引:2,自引:0,他引:2
建立了成流泄漏燃料在热壁上的蒸发与着火模型,分析了泄漏燃料在热壁上的沸腾模式,得到了蒸气离开液面时初始条件的计算方法.采用大涡模拟计算了不同热壁温度时,热壁上方空气的温度分布,并以正十六烷为例计算分析了蒸气在热壁上方发生着火的条件,得到了泄漏燃油在热壁上发生着火的时间与着火点高度. 相似文献
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Masayuki Kaneda Yusuke Matsushima Kazuhiko Suga 《Numerical Heat Transfer, Part A: Applications》2013,63(2):98-113
Convection inside a polymer solution sessile droplet under a strong magnetic field is numerically studied. The droplet presumed is a diamagnetism solution, which has different magnetic susceptibility between solute and solvent. The magnetic field is presumed by a single electric coil. The coil placed in a lower position induces the upward force near the surface, which enhances the Marangoni convection. If the coil is located above the droplet, the flow is suppressed by the downward force. These effects are found to be remarkable for a large droplet. 相似文献
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状态方程对高温高压条件下燃料液滴蒸发计算的影响 总被引:1,自引:0,他引:1
以实际气体状态方程为基础,建立了单个液滴的高压蒸发模型和数值计算方法,并对庚烷液滴在氮气中的蒸发过程进行了模拟计算.重点研究了RK、SRK、PR三种状态方程对高温高压条件下燃料液滴蒸发计算的影响.结果表明,PR方程在气液相平衡、热物性参数以及液滴直径变化历程的计算上都与试验数据有很好的一致性;SRK方程在气液相平衡、二元混合物临界点以及庚烷相变焓的计算上与PR方程的计算结果十分接近,但在热物性参数和液滴蒸发寿命的计算上相比于PR方程的计算结果偏小;RK方程的计算结果与SRK方程和PR方程相比均存在较大偏差.因此,对于建立单个液滴高压蒸发模型而言,PR方程的精度最高,SRK方程次之,RK方程的精度最差. 相似文献
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Complete three-dimensional numerical simulations of single bubble dynamics during flow boiling conditions are carried out using the computational fluid dynamics code FLOW3D based on the volume-of-fluid method. The analyses include a numerically robust kinetic phase-change model and transient wall heat conduction. The simulation approach is calibrated by comparison with available experimental and theoretical data. It is found that the observed hydrodynamics (i.e., bubble shape, departure, and deformation) are simulated very well. The comparison with high-resolution transient temperature measurements during a heating foil experiment indicates that the modeling of the spatiotemporal heat sink distribution during bubble growth requires major attention. The simulation tool is employed for single bubble dynamics during flow boiling on a horizontal heating wall, and the agreement is excellent with published experimental data. The numerical results indicate how bulk flow velocity and wall heat transfer influence the bubble dynamics and heat transfer characteristics. 相似文献
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为了研究自由表面涡流动规律,采用Fluent软件对这一层流流动现象进行了数值模拟。计算中运用流体体积(VOF)模型处理汽水交界面,得到了自由表面涡的流动结构和演化过程,旋涡发展状态与涡量之间的关系。在自由表面涡形成过程中,流体中心区域的涡量随时间不断增大。当涡量达到一定程度时,自由液面处开始出现旋涡,并不断向下延伸直至达到稳定。同时得到了涡核半径、涡核半径处最大切向速度、涡核处环量、涡核内切面速度梯度以及流场中各个速度分量随高度和时间的变化规律。计算结果为了解自由表面涡流动现象提供了一定的参考。 相似文献
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Hochan Hwang 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(6):479-494
A sharp-interface level-set (LS) method is presented for direct numerical simulation (DNS) of particle motion in droplet evaporation. The LS formulation for liquid–gas flows is extended to liquid–gas–solid flows by treating the moving solid region as a high-viscosity fluid phase. The evaporation effect is accurately implemented by imposing the coupled temperature and vapor fraction conditions at the interface. The LS method is tested through computations of particle sedimentation in single-phase and two-phase fluids. The DNS of particle motion in droplet evaporation demonstrates the pinning phenomena of the liquid–gas–solid contact line. 相似文献
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Zeyi JIANG Cuicui LIU Xinxin ZHANG Qiang MA Yusheng SUN .School of Mechanical Engineering University of Science Technology Beijing Beijing China .China Aviation Planning Construction Development Co LTD China 《热科学学报(英文版)》2011,(5)
Flow and heat transfer characteristics of slot jets impingement to a cylindrical convex surface are numerically investigated.Suitable turbulence models have been determined through comparison with the experimental data.Flow structures are described and impingement heat transfer characteristics are discussed.The effects of Re,H/B and D/B on single-slot jets impingement heat transfer are analyzed and heat transfer characteristics of multiple-slot jets are investigated.The results show that:Gas flows along the... 相似文献