共查询到19条相似文献，搜索用时 265 毫秒
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针对煤矿用多级耐磨离心泵中固液两相流动,假定固相颗粒浓度不变,结合SST湍流模型、Euler-Euler非均匀多相流模型进行非稳态计算,主要分析颗粒粒径变化引起的流动演变规律.结果表明随着粒径的增大,叶轮内固体颗粒逐渐向压力面转移,正导叶叶片凸面方向的固体颗粒数量逐渐减少,从而减弱了对壁面的磨损,反导叶内固体颗粒逐渐向叶片凹面聚集.正导叶和过渡区域的湍流动能整体随着粒径的增大而逐渐增大,而反导叶叶片内的湍流动能总体随着粒径的增大而减小.固体颗粒粒径的增大对内流场压力波动的影响,随着级数的增加而逐渐减弱.此分析结果为多级离心泵内的固液两相流动研究提供了参考依据. 相似文献
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应用分子动力学模拟的方法,研究了纳米金刚石颗粒的导热系数对温度和颗粒尺寸的依存关系。为了得到较为准确的模拟结果,采用了平衡态分子动力学模拟的方法。计算了较长时间的热流自相关函数,并得到了导热系数的收敛结果。结果表明,纳米金刚石颗粒由于尺寸的影响,导热系数低于体材料金刚石的导热系数;随温度的升高,导热系数出现一个峰值,该峰值点的温度小于体材料金刚石出现峰值点的温度;随颗粒尺寸的增大,导热系数增加,我们预测导热系数将在一定的颗粒尺寸时收敛于体材料金刚石的导热系数。 相似文献
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纳米流体脉动热管的性能实验研究 总被引：2，自引：0，他引：2
建立了脉动热管的可视化实验台,对以体积分数为1%的TiO2/H2O和CuO/H2O纳米流体及基流体为工质,55％充液率的脉动热管性能进行了实验研究。结果表明,工质静止时,纳米颗粒在脉动热管中会发生沉淀,但工质的运动能够使沉淀纳米颗粒再次悬浮,随着温度的升高,纳米颗粒悬浮性稳定减弱;与基流体工质相比,纳米流体脉动热管的最小启动功率低,启动时间较短,工作温度低,传热热阻小,温度波动振幅小、频率高;纳米流体能大幅提高脉动热管的传热性能,工作温度为110℃时,蒸馏水、TiO2/H2O及CuO/H2O脉动热管的传热热阻分别为0.23℃/W,0.11℃/W和0.13℃/W;两种纳米流体脉动热管的传热性能接近。 相似文献
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文章以有机蒙脱土和醋酸乙烯酯单体为原料,通过悬浮聚合制备聚醋酸乙烯酯/蒙脱土(PVAc/OMMT)复合材料,研究了OMMT对复合粒子表面形态、热学性能和粒度分布的影响,并通过FTIR和XRD对产物进一步研究。结果表明,纯PVAc呈光滑表面的球状形态,而PVAc/OMMT为具有粗糙表面的立方体形状颗粒。另外,复合粒子的粒度显著增大,分散性更好。然而,当粘土含量超过2.5wt%后,复合粒子的平均粒径开始下降,且粒度分布更广。TGA分析表明复合材料的热学性能显著提高。 相似文献
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铜/铝复合材料及其界面研究 总被引：1，自引：0，他引：1
采用固-液复合法制备了钢／铝复合材料,并对钢/铝复合界面进行了研究。结果表明,在适当的预处理工艺下,当铜板预热温度沟400℃,铝液浇注温度为680℃时,可以获得铜／铅界面结合良好的复备材料。 相似文献
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本文采用搅拌法,向熔融状态下的铝锰合金中添加Al2O3颗粒,制备成颗粒增强复合材料。将铝锰合金和复合材料的硬度及两种试样的断口冲击韧性进行对比试验;将铝锰合金和复合材料在加有磨粒的高矿化度水条件下进行磨损试验,比较两种材料的质量磨损量在不同载荷条件下变化。试验表明：颗粒增强复合材料的硬度相对合金基体来说有了显著的提高;从冲击断口来进行分析,颗粒增强体的加入有细化晶粒的作用;锰合金及其复合材料的质量磨损量都是随着载荷的增大而增大,在较大载荷的条件下（〉110N）,复合材料的在较大载荷的条件下远远大于铝锰合金的耐磨性。 相似文献
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《科技通报》2017,(3)
通过非均匀磁场诱导磁流体中非磁性颗粒定向移动实现分离的磁泳技术,在微流控芯片中用于细胞分选、DNA提纯和生物分析等方面具有潜在的应用价值。考虑稀磁流体的体积分数为1%,其粘性随磁场强度的变化为线性,在此基础上分析了非磁性颗粒在磁流体中的粘性阻力和磁浮力,同时根据流体力学方程组、Maxwell磁学方程组和非磁性颗粒的运动方程,建立了梯度磁场和流场共同作用下的非磁性颗粒运动的二维数值模型。对两种磁场分布下非磁性微粒的运动特性以及不同入口速度和磁场强度对颗粒偏转的影响进行了数值研究。结果表明,磁场驱动非磁性微粒朝着远离磁源的方向移动;入口流速从1.0 mm/s增大到2.0 mm/s时,粒径分别为3、4、5μm的三种颗粒的偏转距离逐渐靠近;微通道内颗粒越靠近磁源位置磁力越大,磁力最大值发生在永磁体相邻两直角附近,所以越靠近磁源的颗粒偏转也越大。另外,在相同入口速度下,磁场强度越大,非磁性颗粒的偏距就越大,越有利于颗粒的负磁泳操作。研究结果对分离装置的设计具有指导意义。 相似文献
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目前对电子烟的关键部件-雾化室的工作性能研究较少。为了找出消费者所反映的问题关键,采用FLUENT流体计算软件模拟了电子烟雾化室的温度、相比例等参数与时间的关系:当时间t=30s时,雾化气体出口面面积加权温度达到了333.74K。减小电阻丝单位面积功率或者硅胶热传导系数,均可使得气体通道区域液相体积比减少。电阻丝功率为5.6×106W.m-2时,雾化气体出口面面积加权温度为329.54K,当硅胶热传导系数由0.35J.K-1.m-1减小到0.20J.K-1.m-1时,雾化气体出口面面积加权温度为333.70K。 相似文献
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The thermal conductivity of two-dimensional materials, such as graphene, typically decreases when tensile strain is applied, which softens their phonon modes. Here, we report an anomalous strain effect on the thermal conductivity of monolayer silicene, a representative low-buckled two-dimensional (LB-2D) material. ReaxFF-based molecular dynamics simulations are performed to show that biaxially stretched monolayer silicene exhibits a remarkable increase in thermal conductivity, by as much as 10 times the freestanding value, with increasing applied strain in the range of [0, 0.1], which is attributed to increased contributions from long-wavelength phonons. A further increase in strain in the range of [0.11, 0.18] results in a plateau of the thermal conductivity in an oscillatory manner, governed by a unique dynamic bonding behavior under extreme loading. This anomalous effect reveals new physical insights into the thermal properties of LB-2D materials and may provide some guidelines for designing heat management and energy conversion devices based on such materials. 相似文献
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Moncef Aouadi 《Journal of The Franklin Institute》2012,349(1):128-139
In this paper we investigate some qualitative aspects of the solutions of a new theory of thermoelasticity with voids based on the concept of volume fraction derived by Cicco and Diaco [A theory of thermoelasticity with voids without energy dissipation, J. Thermal Stresses 25 (2002) 493–503]. This theory has been established in the frame work of linear thermoelasticity without energy dissipation. The theory permits the propagation of heat as thermal waves at finite speed. By means of the logarithmic convexity method a uniqueness theorem is proved. With the help of the semigroup theory of linear operators an existence result is obtained. 相似文献
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Hasan Ebrahimi Shahmabadi Seyed Kazem Bagherpour Doun Seyed Ebrahim Alavi Mehri Mortazavi Zahra Saffari Maryam Farahnak Azim Akbarzadeh 《Indian journal of clinical biochemistry : IJCB》2014,29(3):357-361
Emulsion polymerization was used to synthesize poly butyl cyanoacrylate nanoparticles in presence of steric stabilizer dextran 70. Nanoparticles were characterized by particle size analysis, scanning electron microscopy and light microscopy. Polymerization factors affecting particle size and distribution such as dextran 70, polysorbate 80 (PS 80) and H+ concentration, polymerization time and temperature, and sonication were studied. Distinct concentrations of stabilizer were needed to produce proper nanoparticles. In this case, the appropriate value was 2 % of total volume. At pH 4 significant decrease in production efficiency demonstrated the substantial effect of H+ concentration on nanoparticles. Furthermore significant increases in particle size and distribution was observed at 50 °C compared to room temperature. 0.001 % (v/v) PS 80 represented notable influence on size and distribution. In addition, shaped nanoparticles were obtained by altering polymerization time from 5.5 h to 18 h. Finally, nanoparticle features were influenced by different factors. Appropriate manipulating of such factors can lead to obtaining desirable nanoparticles. 相似文献
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An elaborate experimental set up is described that was used to measure the thermal expiration curves of heat recuperators, that had been constructed with guard heaters and vacuum insulation to minimize heat losses. A much more general model is used along with a precision numerical analysis technique to show that a film coefficient correlation of the Dittus-Boelter type did an excellent job of representing the results from 162 runs in which three feed gas temperatures, two flow rates, two particle size ranges, one bed diameter and five desciccants were used. For comparison sake the reported film coefficient correlation is finally assembled in a table along with others found in the literature. 相似文献
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石家庄市秋季可吸入颗粒物垂直分布特征的研究 总被引：3，自引：0，他引：3
本文研究了石家庄市秋季可吸入颗粒物质量浓度垂直分布和粒度分布特征。结果表明，环境空气中可吸入颗粒物的众径为0.2μm～1.0μm，比表面积为3536.2～4396.06 m2/kg，PM2.5/PM10高达71.28％～81.14％； 细小颗粒物累积百分含量随高度增加而增加，PM2.5和PM10累积分布随高度增加呈现出对数增加的规律；采样高度1.5m时中位径（D50）>1μm，大于1.5m时 D50均<1μm。不同高度降尘的比表面积为336.55～790.06m2/kg，PM2.5/PM10为19.46～22.47％，D50为9.66～13.78μm，D98在34.93～53.48μm之间。 相似文献
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一种改进的遥感热惯量模型初探 总被引：6，自引：0，他引：6
本文改进了遥感热惯量模型 ,考虑到植被因素的影响 ,在植被覆盖区 ,使用双层模型中的土壤热能量平衡方程 ,同时在热传导方程的边界条件中引进显热通量和潜热通量 ,使热惯量模型的应用范围从裸土扩展到植被覆盖区 .通过顺义地区的MODIS影像数据和同步野外测量数据对此模型进行验证 ,所获得的热惯量值与实测热惯量值进行比较 ,结果表明改进模型的实用性和可行性 . 相似文献
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C. K. Liu 《Journal of The Franklin Institute》1985,320(6)
Squire's study of thermal stability of a solid infinite cylinder with temperature-sensitive internal heat generation is extended to a hollow infinite cylinder, subject to combinations of four commonly encountered boundary conditions. The results of these analyses indicate that the critical parameter for thermal viability is critically dependent on the cylinder size, the convective heat transfer coefficient and other constants accrued from the cylinder environment. In certain situations, such as a frigid climate, a hollow Squire cylinder is thermally viable only if it is thicker than a critical thickness. 相似文献
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Optical chromatography relies on the balance between the opposing optical and fluid drag forces acting on a particle. A typical configuration involves a loosely focused laser directly counter to the flow of particle-laden fluid passing through a microfluidic device. This equilibrium depends on the intrinsic properties of the particle, including size, shape, and refractive index. As such, uniquely fine separations are possible using this technique. Here, we demonstrate how matching the diameter of a microfluidic flow channel to that of the focusing laser in concert with a unique microfluidic platform can be used as a method to fractionate closely related particles in a mixed sample. This microfluidic network allows for a monodisperse sample of both polystyrene and poly(methyl methacrylate) spheres to be injected, hydrodynamically focused, and completely separated. To test the limit of separation, a mixed polystyrene sample containing two particles varying in diameter by less than 0.5 μm was run in the system. The analysis of the resulting separation sets the framework for continued work to perform ultra-fine separations. 相似文献