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介绍了EAST中超导磁体的CICC结构型式及其性能参数;并对低温试验装置流程作了简述,并在低温试验中测量了超临界氦通过的摩擦系数与压力损失,最后将实验值与经验拟合公式进行了比较。 相似文献
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气体在微细多孔介质中的流动阻力研究 总被引:2,自引:0,他引:2
本文对空气、氢气和氦气流过微细多孔介质内部的流动阻力特性进行了实验研究,分析不同气体在不同颗粒直径条件下摩擦因子与等效雷诺数的关系.结果表明:对于空气、氢气和氦气,当颗粒直径为225μm和125μm时,由于可压缩性的影响,摩擦因子略大于经验公式结果.对于空气,当颗粒直径为90μm和40μm时,实验得到的摩擦因子小于经验公式结果.对于氢气和氦气,当颗粒直径为125μm时,经过可压缩性修正的摩擦因子实验值略小于经验公式结果;颗粒直径为90μm和40μm时,摩擦因子小于经验公式结果.因此,对于空气、氢气和氦气,当颗粒平均直径小于90μm时,微细多孔介质中的流动特性存在稀薄气体效应. 相似文献
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微型管内流动特性的实验研究 总被引:5,自引:0,他引:5
以四氯化碳作为工质,流经内径分别为0.168 mm、0.399 mm、0.799 mm不锈钢管及内径分别为0.242 mm、0.315 mm、0.520 mm石英玻璃管,测量压降与流量的关系,从而获得摩擦因子f与雷诺数Re的关系。实验结果表明, 当雷诺数Re小于1600-1800时,除内径为0.168 mm的不锈钢管外,别的内径的微管内的摩擦因子与经典层流理论值几乎一致,而内径为0.168 mm的不锈钢管由于更大的相对粗糙度(8%-10%左右),其f值比经典理论值高约5%-10% 左右。当雷诺数Re越过1800时,f的值明显偏离经典层流理论值。 相似文献
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流体在微细多孔介质中的流动阻力研究 总被引:2,自引:0,他引:2
本文对空气和水流过烧结微细多孔介质内部的流动阻力进行了实验研究和数值模拟,分析不同颗粒直径条件下摩擦因子与等效雷诺数的关系.结果表明:对于水,实验及数值模拟得到的摩擦因子与经验公式符合很好.对于空气,当颗粒直径为200μm和125 μm时,由于可压缩性的影响,摩擦因子略大于经验公式结果.当颗粒直径为90μm和40 μm时,实验及考虑速度滑移得到的摩擦因子小于经验公式结果.因此,当颗粒平均直径小于90 μm时,空气在微细多孔介质中的流动需要考虑稀薄气体效应. 相似文献
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本文采用局部非热平衡模型对发汗冷却过程中多孔壁面内的换热和流动进行了数值模拟,分析了影响多孔介质内固体骨架与流体的温度及温差分布的因素,研究了这些因素对发汗冷却过程的影响规律.计算结果表明:增大固体骨架的导热系数、增大冷却剂流速或者加强冷端换热有利于提高发汗冷却效率. 相似文献
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Microfluidic devices are used today in many engineering applications. However, despite much progress in this field, the fundamental understanding of fluid flow and heat transfer on the microscale is still not satisfactory. In this study, the rarefaction effects on the pressure drop for an incompressible flow through silicon microchannels having a rectangular, trapezoidal or double-trapezoidal cross-section are investigated. The roles of the Knudsen number and the cross-section aspect ratio in the friction factor reduction due to the rarefaction are pointed out. 相似文献
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In this present study, an experimental investigation has been carried out for a roughened double-pass solar air heater. The respective variation in other parameters, such as relative roughness pitch (p/e), relative roughness height (e/Dh), and angle of attack (α), were 5–20, 0.022–0.044, and 30°–75°, respectively. The effect of roughness and operating parameters on Nusselt number (Nu) and friction factor (f) has been determined, and the results are compared with those of a smooth absorber plate; considerable enhancement in both heat transfer and friction factor is noticed. Utilizing these experimental data, correlations for Nusselt number and friction factor correlations were also developed. 相似文献
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基于欧拉法建立了冰浆流动的混合模型,对冰浆在90°弯管内的流动特性进行了数值模拟研究,获得了弯管内冰浆的流场和冰晶颗粒的运动轨迹,探讨了弯管管径、曲率半径及冰浆的流速、浓度参数对弯管内冰浆压降的影响,并对弯管压降的模拟结果与实验结果进行对比,两者吻合较好。结果表明:在计算参数范围内,弯管压降随冰浆流速、浓度及弯管曲率半径的增大而增大,随弯管管径的增大而减小;冰浆在弯管内流动形成二次流现象,两个漩涡区域出现在弯管截面两侧;漩涡导致部分冰晶颗粒的运动轨迹发生改变,并使其向弯管下方的负压区聚集,增大了冰晶颗粒的碰撞几率。 相似文献
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This study has compared the convection heat transfer of Water-based fluid flow with that of Water-Copper oxide (CuO) nanofluid in a sinusoidal channel with a porous medium. The heat flux in the lower and upper walls has been assumed constant, and the flow has been assumed to be two-dimensional, steady, laminar, and incompressible. The governing equations include equations of continuity, momentum, and energy. The assumption of thermal equilibrium has been considered between the porous medium and the fluid. The effects of the parameters, Reynolds number and Darcy number on the thermal performance of the channel, have been investigated. The results of this study show that the presence of a porous medium in a channel, as well as adding nanoparticles to the base fluid, increases the Nusselt number and the convection heat transfer coefficient. Also the results show that As the Reynolds number increases, the temperature gradient increases. In addition, changes in this parameter are greater in the throat of the flow than in convex regions due to changes in the channel geometry. In addition, porous regions reduce the temperature difference, which in turn increases the convective heat transfer coefficient. 相似文献
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Sílvia C. Hirata 《Physics letters. A》2010,374(26):2661-4613
By using the mathematical formalism of absolute and convective instabilities we study the nature of unstable three-dimensional disturbances of viscoelastic flow convection in a porous medium with horizontal through-flow and vertical temperature gradient. Temporal stability analysis reveals that among three-dimensional (3D) modes the pure down-stream transverse rolls are favored for the onset of convection. In addition, by considering a spatiotemporal stability approach we found that all unstable 3D modes are convectively unstable except the transverse rolls which may experience a transition to absolute instability. The combined influence of through-flow and elastic parameters on the absolute instability threshold, wave number and frequency is then determined, and results are compared to those of a Newtonian fluid. 相似文献
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B. B. Vilenchits A. A. Zhdanovskii N. I. Lemesh L. A. Senchuk 《Journal of Applied Spectroscopy》1997,64(3):399-402
An experimental study is carried out to investigate a bilateral direct-flow vortex tube of small (0.3–3.0)·10−2 m) size and to compare its optical properties with those characteristics of vortex tubes of a larger ((3–16)\10−2 m) scale. A model is suggested for forming transverse profiles of the intensity of laser beams with an intensity hole in
the center and of annular beams.
Translated from Zhural Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 386–389, May–June, 1997 相似文献