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81.
Plate fin-and-tube heat exchangers operate in a cross-flow arrangement with the complex path of gas flow, hence in order to determine the velocity field and heat transfer characteristics, the numerical methods must be used. The CFD codes allow obtaining local values of the heat transfer coefficient, however it is impossible to incorporate these values into the analytical formulas for the overall heat transfer coefficient, that is fundamental for the designing procedure of the cross-flow heat exchangers. Therefore this paper presents a method for determination of the average heat transfer coefficient for gas flow in a plate fin-and-tube heat exchanger using the CFD simulations. The values of the heat transfer coefficient obtained using the heat transfer formulas for the Nusselt number, determined with the CFD simulations, can be directly implemented in the thermal designing procedure of the cross-flow heat exchangers. The results of the numerical computations are validated experimentally. 相似文献
82.
Zhi-Hua Yin Yun-Ze Long Chang-Zhi Gu Mei-Xiang Wan Jean-Luc Duvail 《Nanoscale research letters》2009,4(1):63-69
In this paper, we focus on current–voltage (I–V) characteristics in several kinds of quasi-one-dimensional (quasi-1D) nanofibers to investigate their electronic transport
properties covering a wide temperature range from 300 down to 2 K. Since the complex structures composed of ordered conductive
regions in series with disordered barriers in conducting polymer nanotubes/wires and CdS nanowires, all measured nonlinear
I–V characteristics show temperature and field-dependent features and are well fitted to the extended fluctuation-induced tunneling
and thermal excitation model (Kaiser expression). However, we find that there are surprisingly similar deviations emerged
between the I–V data and fitting curves at the low bias voltages and low temperatures, which can be possibly ascribed to the electron–electron
interaction in such quasi-1D systems with inhomogeneous nanostructures. 相似文献
83.
《The IES Journal Part A: Civil & Structural Engineering》2013,6(2):165-172
Based on the general theory of concrete filled steel tube (CFT), nonlinear analysis of large size CFT is performed using ANSYS, a commercially available finite element (FE) programme. A nonlinear 3-D finite element analysis (FEA) model is developed to predict the behaviour of axially loaded CFT columns. Comparisons between the predicted results and the curves of axially loaded CFT column published in the open literature show that the trend of the curves fit well. This also shows that the constitutive relation model and the basic assumptions can accurately predict the behaviour of the large size CFT. The FEA model is then used to investigate the influence of steel tube wall thickness, the width to thickness of built-in stiffener for ultimate bearing capacity of large size square CFT and so on. In addition, the whole construction process of large size rectangular CFT with holes in the middle vertical plate is analysed. The study presents the main influential factors for CFT ultimate bearing capacity and the concrete crack distribution. 相似文献
84.
Chiranjeeva Rao Seela B. Ravisankar 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(21):2564-2571
This work investigates the suspension duration of the nanosized multiwalled carbon nanotubes (MWCNT) and aluminum oxide (Al2O3) in B20, B50 and B70 blends of Jatropha Methyl ester. The MWCNT and aluminum oxide (Al2O3) are added to the fuel blends in the proportions of 50 and 100 pmm separately by ultra sonication. The prepared fuel samples are characterized, and turbidity analysis was done to find the stability rate of nano-additives. The outcomes reveal the maximum stability rate for MWCNT and Al2O3 as 83.3% and 87.03%, respectively, with 50ppm in B20 over a period of eighteen days. A considerable drop in suspension was observed with the 100 ppm MWCNT and Al2O3 biodiesel blends. 相似文献
85.
86.
阐述了双钢管混凝土的研究现状,比较单钢管混凝土分析了双钢管混凝土柱的受力机理,探讨双钢管混凝土在极限状态下混凝土和钢管各自的应力状态。由于双钢管混凝土柱中有两个不同的钢管嵌套,其承载力必然与它们的组合效果有关。引入体积变形系数得出截面形式的最佳组合状态,可供工程设计应用参考。 相似文献
87.
本文论述新型多孔插式管式喷丝板的设计、制造工艺及其应用特点。多孔喷丝板的研制成功为中空纤维膜技术向工业化、实用化方向发展开阔了良好的前景。 相似文献
88.
陈民 《四川大学学报(工程科学版)》1989,(5)
本文引用圆环壳弯曲方程一般解.计算了有实用价值的S型波纹管纯弯曲应力和位移。着重研究了与波纹管设计及应用有关的最主要参数,即最大应力和刚度随S型波纹管初相角变化情况。 相似文献
89.
许多工程结构应用了双螺旋弹簧质量系统(如炮闩的复进簧),这种系统的非线性动态响应分析的解法国内外尚属罕见;本文分析计算了在纵向冲击载荷作用下,双螺旋弹簧质量系统中的动态应力变化规律及其最大值;理论计算结果与实验符合良好.这种方法可用来进行双螺旋弹簧质量系统的动态强度设计计算. 相似文献
90.
马善定 《武汉大学学报(工学版)》1986,(5)
坝内钢管在水电站中应用广泛,但现行的设计理论和方法一般偏于保守,更难于适应大容量、高水头电站的发展,本文根据理论分析和试验研究,提出了改进坝内钢管强度设计的具体措施和方向,对工程设计和进一步开展科学研究,具有实际意义。 相似文献