共查询到20条相似文献,搜索用时 78 毫秒
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使用热侵蚀沉积粒子程序(HEDPIC)模拟了由小块沿环向表面倾斜的瓦片组成类 ITER 偏滤器的极向
缝隙附近瓦片表面的热流密度分布,研究了不同倾斜高度对热流密度分布的影响。研究结果表明,当瓦片设置成
合适的倾斜角度时,瓦片上表面靠近缝隙附近的电子热通量为零;离子热流密度小于上表面远离缝隙的热流密度,
棱边处热流密度过高的问题得到解决。 相似文献
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Ting Guo XiongWei Yang Qian Geng Zhen Li YueMing Li Xian Wang Hu Zhang 《中国科学:物理学 力学 天文学(英文版)》2020,(2):93-103
This study presents a two-dimensional phononic crystal with heat flux manipulation and wide bandgaps of out-of-plane modes within the low-frequency range. The anisotropic matrix made of spiral-multilayered materials with different thermal conductivities, and the coating layer inserted with metal are designed for heat flux manipulation. Rubber-coated metal cylinders are periodically embedded in the anisotropic matrix to obtain the low-frequency bandgaps of out-of-plane modes. Numerical simulation is carried out to validate the heat and elastic characteristics of the spiral-multilayered anisotropic structure and reveal the effects of the laying angle and temperature on the bandgaps. Subsequently, a spiral-multilayered plate with periodic structures is studied, which shows an obvious vibration attenuation in the frequency ranges of the bandgaps and a deflected heat flux from the initial propagation direction. In the experimental investigation, the multi-phase spiral-multilayered anisotropic plate is simplified to a single-phase anisotropic plate made of aluminum. The characteristics of this type of anisotropic phononic crystal structure may pave the way for the design of a new kind of thermo-acoustic metamaterial serving in combined thermal and acoustic environments. 相似文献
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Yanagita T 《Chaos (Woodbury, N.Y.)》1992,2(3):343-350
A minimal model for boiling is proposed. With increasing temperature of a bottom plate, the model shows three successive phases; conduction, nucleate, and film boiling. In the nucleate regime the heat flux increases with the temperature of the bottom plate, while it decreases in the film boiling regime. In the boiling phase, the maximum Lyapunov exponent is positive, implying that the boiling phenomena are spatiotemporally chaotic. 相似文献
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针对高超声速飞行器前缘疏导式防热结构的特点,设计前缘内嵌高导热率材料结构和一体化层板热管结构两类对比实验,用于验证前缘疏导式防热结构的可行性.利用球形短弧氙灯作为辐射热源模拟气动加热,分别对钢质前缘、内嵌铜材料的钢质前缘和一体化层板式热管前缘进行加热,测量前缘驻点区域和尾部翼面区域的温度变化.实验结果表明:内嵌高导热率材料的前缘疏导结构能够降低头部驻点区的温度,提高尾部低温区的温度,实现对前缘结构的热防护;以蒸馏水作为工质一体化层板式热管前缘结构,在较低热流条件下也能够实现对前缘驻点区的疏导式热防护,但在较高热流条件下,由于水蒸气压力过大使得层板式前缘结构发生破坏,体现出热管内部工作介质对结构防热效果和应用范围都起到的关键作用. 相似文献
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Flame impingement heat transfer has widespread industrial and domestic applications and attaining high heat flux as well as low emission of pollutants is the important prerequisite for all such applications. In this article, the heat transfer and emission characteristics of a laminar flame jet impinging on a flat target plate have been investigated experimentally. The effect of reactant jet Reynolds number, equivalence ratio and burner to plate separation distance on the average heat flux, and emissions of CO and NOx are studied using methane and ethylene fuels. Results indicate that the heat flux is maximized under certain operating conditions of jet Re, equivalence ratio, and separation distance between the burner and the target. Fuel type is found to have an effect on the heat transfer rate because of the varying luminosity of the flame with different fuels. Operating regimes that produce lower emission of pollutants are also identified. Findings of this article have direct industrial relevance to flame impingement heat transfer applications that have small target plate-to-burner port diameter ratios. 相似文献
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A. A. Abramov A. V. Butkovskii 《Journal of Experimental and Theoretical Physics》2013,116(6):1036-1042
Based on numerical solution of the Boltzmann equation by direct statistic simulation, the Couette flow with heat transfer is studied in a broad range of ratios of plate temperatures and Mach numbers of a moving plate. Flow regime classification by the form of the dependences of the energy flux and friction stress on the Knudsen number Kn is proposed. These dependences can be simultaneously monotonic and nonmonotonic and have maxima. Situations are possible in which the dependence of the energy flux transferred to a plate on Kn has a minimum, while the dependence of the friction stress is monotonic or even has a maximum. Also, regimes exist in which the dependence of the energy flux on Kn has a maximum, while the dependence of the friction stress is monotonic, and vice versa. 相似文献
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The influence of the plate inclination angle relative to the horizon on a distance between formed rivulets and breakdown of
a falling water film was studied experimentally on a heater of 150×150 mm. Dependences of the distance between rivulets on
the heat flux density and plate inclination angle were examined. In experiments two zones of influence of the heat flux on
a distance between rivulets were revealed: at θ ≥ 20° distances between the rivulets do not depend on the heat flux, and at θ ≤ 15° they decrease with a rise of the heat flux. Data on film breakdown were generalized with consideration of evaporation
effect. It is shown that there is almost no effect of inclination angle on film breakdown in the whole range of studied Reynolds
numbers.
The work was financially supported by the President of RF (No. NSh-6749.2006.8), Russian Foundation for Basic Research (Grants
Nos. 05-08-33325-a, 06-01-00360-a) and SB RAS (Interdisciplinary integration project No. 111). 相似文献
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本文采用组合扩散系数方法处理不同气体组分之间的扩散,对氩等离子体的流射入空气环境并撞击平板时的层流流动和传热进行了数值模拟.这种新的处理混合气体中质量扩散的方法有助于更准确地描述等离子体条件下的组分扩散与能量输运。文中给出了射流中速度、温度及氩质量分数的分布情况,以及基板处热流密度分布的若干典型的数值模拟结果. 相似文献
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针对展向凹槽和泄流孔对高超声速钝平板边界层转捩的影响,在中国空气动力研究与发展中心F2 m激波风洞(FD-14A)开展了试验及初步的计算与理论研究.试验的来流马赫数为6、单位雷诺数为3.3×107/m,平板的前缘半径为1 mm,攻角为–4°.在距平板前缘110 mm处布置三组不同的二维展向凹槽,凹槽的宽度与深度分别为凹槽1(2.5 mm,1 mm)、凹槽2(3.75 mm,1.5 mm)、凹槽3(5 mm,2 mm),同时凹槽1的两端可以打开泄流孔,记为凹槽4,不含凹槽时的光滑平板情况记为凹槽5或平板.采用热流传感器测量了不同情况下平板中心线的热流分布,测量结果显示,光滑平板情况在x≈340 mm处开始转捩,在x≈425 mm处转捩接近完成.凹槽导致平板边界层的转捩位置提前,且随着凹槽宽度及深度的增加,对转捩的促进作用增强,转捩位置向上游移动.凹槽1增加泄流孔后(凹槽4)其热流分布及转捩位置与光滑平板情况基本一致.边界层流动完全转捩为湍流后,各情况下的热流差别较小,表明不同规格的凹槽只影响转捩过程中的热流分布,对转捩完成后的湍流壁面热流影响较小.数值计算(CFD)结果显示,泄流孔导致了被动抽吸,试验结果显示凹槽两端的泄流孔抽吸效应抵消了凹槽对平板中心线边界层转捩的促进作用.采用线性稳定性理论(LST)及最优扰动方法分析了光滑钝平板情况的流动失稳机制.LST结果显示,本文平板流动不存在Mack第一模态、第二模态失稳,因此传统的模态失稳机制无法解释试验中观测到的转捩现象.最优扰动计算显示,平板流动存在较强的非模态失稳,可以定性解释观测到的转捩现象. 相似文献
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《中国物理快报》2017,(9)
Based on the surface temperature measured by the infrared camera on the experimental advanced superconducting tokamak(EAST), the heat fluxes on the lower outer divertor target plate during H-mode with the lower-hybrid wave current drive(LHCD) only and with the LHCD combined with the neutral beam injection(NBI) are calculated by the DFLUX code and compared. The analyzed discharges are lower single null divertor configuration discharges. In the case with the LHCD only(I_p~400 kA, P_(LHCD)~2 MW), ELM-free appears after L-H transition with the peak heat flux on the lower outer target plate less than 1 MW/m2. However, there is no ELMfree appearing after the L-H transition in the case with the LHCD+NBI(I_P~300 kA, P_(LHCD)+P_(NBI)~2 MW).The results show that the peak heat fluxes on the lower outer target plate in the LHCD+NBI H-mode cases are larger than those in the LHCD H-mode under the similar auxiliary heating power. This is because the heat flux profiles of the lower outer target plate as a function of plate location in ELMing with the LHCD+NBI are narrower than those with the LHCD only. The results are consistent with the results in terms of the scrape-off layer width observed in the EAST. 相似文献
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高超声速飞行器面临剧烈的气动加热环境, 电弧风洞是飞行器防热材料地面考核筛选的主力设备。热流密度是电弧风洞重要的模拟参数之一, 需要进行准确有效的测量。针对电弧风洞气流环境特点, 开展传统塞式量热计和新型同轴热电偶的对比测热试验, 并采用数值模拟对两种热流传感器的传热特性进行了分析。在电弧风洞平板自由射流试验热流密度分布在0~1 100 kW/m2范围内, 同轴热电偶的热流密度测试试验结果相对塞式量热计偏低10%~15%。数值模拟结果表明, 塞式量热计本身结构热物性参数不匹配会导致热流密度测量数值偏高至少10%, 而同轴热电偶测量数值偏高最大仅为2.19%, 相对塞式量热计具备更高的测量精度。同时, 电弧风洞中不同材质热流密度测试模型使用同轴热电偶进行测热试验时, 需要在同轴热电偶同模型之间增加适当厚度的不锈钢套以满足传感器周围环境的热匹配。 相似文献
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The current study centralizes on unsteady free convection slip flow of Casson fluid past a vertical permeable plate with Hall current, radiative heat flux, and variable suction. The nonlinear convection is subjected to quartic order. Perturbation method is used to convert the non-linear coupled partial differential equation of the momentum and energy to a system of ordinary differential equations. The dimensionless governing equations are solved analytically for velocity and temperature profiles. The graphs are plotted for sundry parameters for variations in the distinct flow fields w.r.t distance from the plate. Variation in the skin friction for the axial and transverse cases are presented in the form of graphs for various parameters. It is observed that with the increase in the order of non-linear convection and value of radiation parameter, the velocity field increases in Casson fluid. The increase in heat absorption parameter and Prandtl number decreases the temperature profile and increase in radiative heat flux parameter increases the temperature profile. 相似文献
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Spray cooling is an effective tool to dissipate high heat fluxes from hot surfaces. This article thoroughly investigates the effect of thickness of a hot stainless steel plate on the cooling time, cooling rate, heat flux, and heat transfer coefficient under constant mass flow rate maintained at 1 MPa using water as the coolant. Cylindrical samples of stainless steel with constant diameter (D = 25 mm) and thickness (δ = 7.5, 12, 16.5, and 21 mm) were used in the present study. Critical droplet diameter to achieve an ultra-fast cooling rate of 300°C/s was estimated by using an analytical model for samples of varying thicknesses. The analytical model (one side spray cooling) showed good agreement with experimental results with a relative error of 3.2% in the plate thickness range of 1–12 mm. An increasing trend in maximum heat flux was found with increasing thickness of the plate. Maximum heat flux as high as 1,800 kW/m2 was achieved for a 21-mm-thick sample. Heat transfer coefficients in the range 0.092–96.24 kW/m2K, 0.111–98.9 kW/m2K, 0.074–63.4 kW/m2K, and 0.127–55.63 kW/m2K were reported for sample of varying thicknesses in the present study. Limited published work is available with reference to water spray cooling dynamics and thickness of stainless steel plate. Therefore, the present study focuses on the correlation between the thickness of the plate and spray dynamics of water spray cooling. 相似文献