共查询到17条相似文献,搜索用时 93 毫秒
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运用重整化(RNG)的κ-ε模型对半封闭板内带旋流的射流冲击凸台的传热及流动进行仿真,研究了旋转射流冲击凸台时的流场特性以及凸台表面、侧壁和平板上的传热特性.分析了旋流强度(旋转数)、流动Re数、冲击高度H/D对传热与流动的影响.结果表明,不同Re数下旋流会削弱驻点处的冲击作用,从而使得驻点处的传热Nu数减小.在雷诺数Re=25 000时,在旋转数0相似文献
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采用大涡模拟模型对突扩膨胀射流冲击平板的传热特性及喷嘴内部流场进行数值模拟,得到不同进口Re数,不同膨胀比情况下喷嘴内部流场和射流冲击平板时的换热效果,分析了不同进口Re数、膨胀比E、冲击高度H/d对换热和流动的影响.研究表明,与直喷嘴进行对比,由于膨胀喷嘴射流与周围介质的掺混、渗透作用使射流的流速大大降低,最大速度偏离几何中心,使得换热效果减弱,对加热平板的冷却具有不对称性,但使得整个换热板的平均冷却效果更加均匀. 相似文献
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为了深入理解脉动冲击射流的传热传质特性,研究脉动流的温度相关热物理性质对于靶面局部努塞尔数分布的影响,分别对正弦和方波非稳态脉动冲击射流进行了数值模拟.结果显示单个正弦脉冲的强化传热并不明显,而方波脉冲的强化传热效果却十分明显.对于脉动冲击射流中的流场分析表明,靶面上的瞬态换热效率与非线性热力学和水力学边界层随时间的发展密切相关. 相似文献
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建立微型车室内三维空气流动与传热计算的物理模型和数学模型,应用κ-ε紊流模型、非结构化网格及有限体积法对微型车室内两种回风方式的三维空气流场与温度场进行数值模拟仿真计算与对比分析,为微型车的空调环境优化研究提供有益的参考. 相似文献
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《中国计量学院学报》2015,(1)
设计一种新型旋风-布袋复合除尘器,采用两级复合除尘技术,弥补旋风除尘对于细颗粒去除效率低的不足.通过FLUENT软件提供的RNG K-ε湍流模型对其内部流场进行了数值模拟,并和未加布袋的普通旋风除尘器内部流场进行对比,探明复合除尘器内压力场和速度场基本特征.数值模拟结果表明,新型除尘器内局部湍流数目减少但切向入口处存在较强局部湍流现象;压力场变化较大,压差主要集中在布袋内外两侧.通过对复合除尘器内流场分析,为以后结构进一步优化设计提供依据.此外,复合除尘器采用嵌入式结构,占用空间小,造价低,具有广泛的应用前景. 相似文献
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空调室内三维紊流流动与传热的数值模拟 总被引:3,自引:0,他引:3
采用三维紊流模型,应用有限容积法计算了室内空调的气固耦合传热问题,并对室内空调的气流组织形式,主要是对流速场,温度场进行了数值模拟计算,为空调室内的气流组织形式的优化设计及舒适性提供了研究依据。 相似文献
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与水射流相比,超临界二氧化碳射流破岩具有所需能量少、效率高,以及不产生储层渗透性伤害等优点。将其应用于非常规油气资源的径向井钻井与喷射压裂作业中已引起广泛关注。井底压力环境对水力能量具有严重影响,而超临界二氧化碳流体性质易随环境压力改变而显著变化,是否具有良好射流作业效率仍亟待研究。通过数值模拟与室内测试实验方法,研究了模拟围压对流场速度分布、射流冲击力以及冲蚀破岩效率的影响。结果表明:喷射压力恒定时,射流冲击力和射孔深度均随围压增大而显著减小,二氧化碳临界压力处变化明显;喷射压差恒定时,随着围压的增大,射流冲击力几乎不发生变化,而射孔深度先较稳定或轻微增长然后明显减小,在临界压力时达到最大。分析认为,围压升高引起喷嘴外流场二氧化碳由气态相变为超临界态,射流形式由非淹没射流转变为淹没射流,是超临界二氧化碳射流与水射流冲蚀射孔规律显著不同的主要原因。 相似文献
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P. P. Volosevich I. I. Galiguzova E. I. Levanov E. V. Severina 《Journal of Engineering Physics and Thermophysics》2009,82(2):346-354
The gas-dynamics equations in Lagrangian mass coordinates for a heat flow with a relaxation and a hyperbolic heat transfer
have been considered in the plane-symmetry approximation. The characteristics of the system of these equations were determined.
Relations for the front of a strong discontinuity of its solution were obtained. With the theory of generalized solutions
of quasi-linear equations, the stability of the discontinuities of gas-dynamic and heat quantities characteristic of the indicated
flow was demonstrated.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 350–357, March–April, 2009. 相似文献
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为了研究声波对单圆柱绕流流动和传热特性的影响,建立了流场、声场、对流传热多物理场耦合的二维数学模型,并利用有限元软件COMSOL进行数值模拟。结果表明:(1)当频率f=50 Hz、声压级LSP=123~149 d B时,斯特劳哈尔数Sr随声压级增大而减小,圆柱表面压力系数CP随声压级增大而增大;(2) LSP=143 d B、f=20~80 Hz时,斯特劳哈尔数Sr、压力系数CP均随频率f增大而增大;(3)对比f=50 Hz、LSP=143 d B声波作用与无声波作用的情况,阻力系数CDF和升力系数CDL都呈周期性变化,但有声波作用时振幅增大;(4)声波作用会促进圆柱表面热量传递,但当LSP>143 d B,圆柱表面局部努塞尔数Nuθ开始减小。该研究结果为强化圆柱绕流传热提供了理论研究基础。 相似文献
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Fluid flow and heat transfer characteristics of nanofluids flowing through helically coiled tubes under uniform heat flux condition are studied experimentally. The turbulent flow of two different kinds of nanofluids, i.e. Ag-water and SiO2-water, are examined. Three different helically coiled tubes along with straight ones are constructed to investigate the effects of geometrical parameters such as pitch circle diameter and helical pitch as well as nanoparticle volume concentration. The viscosity and thermal conductivity of nanofluids are determined experimentally in different volume fractions and temperatures. The range of Reynolds number is from 8900 to 11970. The experimental outcomes show that using nanoparticles in coiled tubes can be more effective in improving the heat transfer rate than the straight tube. Empirical correlations are extracted based on experimental data to predict the Nusselt number and friction factor of turbulent nanofluids flow through helically coiled tubes. 相似文献
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通过综述近年冰浆流动特性方面的研究,介绍不同的冰浆模型,并讨论冰浆在管内流动的压降及流型。然后从冰浆导热系数开始,综述冰浆的传热特性,讨论不同表面换热系数和相应的Nusselt数,为研究冰浆的流动和传热特性提供借鉴。 相似文献
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In this study, a new numerical investigation was carried out to study the heat transfer characteristics of nanofluid flow inside a copper helical tube under constant heat flux. A nanofluid with different particle weight concentrations of 0.5%, 1.0%, and 2.0% was used. The effects of different parameters such as Reynolds number, nanofluid particle concentration, and constant heat fluxes (1500 and 3800?W/m2) on heat transfer coefficient were studied. For validation, Nusselt number and convection heat transfer coefficient obtained from the numerical model was compared with the experimental results. Also, to verify the accuracy of the method, grid independency was studied for each heat flux. The observations showed that the heat transfer coefficient increased by using nanofluid instead of base fluid. In addition, the convection heat transfer coefficient performance improved by increasing the nanoparticles’ concentration. The results from the numerical simulation compared with the experimental data showed that this new numerical method has high accuracy and could correctly predict the heat transfer behavior of nanofluids with different weight particle concentrations under constant heat flux. 相似文献