Brownian Motion Effects on Natural Convection of Alumina–Water Nanofluid in 2‐D Enclosure

This article reports a numerical study of natural convection heat transfer in a differentially heated enclosure filled with a Al₂O₃–water nanofluid. Fluent v6.3 is used to simulate nanofluid flow. Simulations have been carried out for the pertinent parameters in the following ranges: the Rayleigh number, Ra = 10⁶, 10⁷, and the volumetric fraction of alumina nanoparticles, ? = 0 ? 4%. The effect of Brownian motion on the heat transfer is considered and examined. The numerical results show a decrease in heat transfer with an increase in particle volume fraction. Similar to experimental results, the Nusselt number increases with the Rayleigh number in the numerical results. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21121     

Experimental analysis and evaluation of a vacuum enclosed concentrated solar thermoelectric generator coupled with a spectrally selective absorber coating

Significant research in the past decade has been focused on quantitatively and qualitatively validating potential of solar thermoelectric modules to harness electricity. In the present study, we have experimentally analysed steady-state temperature variation of a spectrally selective solar absorber coating (α?=?0.954, ε?=?0.13) with variation in solar irradiation flux (concentration ratios?=?39, 50 and 65) using Fresnel lens and vacuum enclosure pressure (200?mbar to 900?mbar in steps of 100?mbar). It is observed that the experimental results so obtained go hand in hand with a COMSOL simulation model of the set-up. Further, we have carried out performance analysis of a solar thermoelectric generator (STEG) set-up enclosed in vacuum conditions equipped with Fresnel lens and absorber set-up coupled to Bi₂Te₃ thermoelectric module array electrically connected in series. The results depict a maximum power output of 0.91?W and a peak efficiency of 2.21% at a hot-side temperature of 642?K.     

Experimental study on transient natural convection in a cube enclosure with an isolated vertical cyclically heated plate

INTRODUCTIONNaturalconvectioninsideenclosuresisatopicofconsiderablecurrentinterestandimportance.Ofparticularinterestarethetransientcoolingproblemsinenclosureswithinternalisolatedheatedbodies,inwhichnaturalconvectionisoftenthedominantheattransfermecha...     

Maximum density effects on buoyancy-driven convection in a porous trapezoidal cavity

A numerical study of the steady buoyancy-induced flow and heat transfer in a trapezoidal cavity filled with a porous medium saturated with cold water at a temperature around 4 °C has been performed. The analysis has been done for a cavity with different aspect ratios ranging from 0.25 to 0.75 and Rayleigh numbers ranging from 100 to 1000 using a finite-difference method. It is found that four cells are formed inside the cavity independent of the Rayleigh number and aspect ratio. The existence of buoyancy force reversal resulting from the maximum density effect, leads to a reduction in the strength of the convective flow and also the average Nusselt number.     

Finite element simulation of magnetoconvection inside a sinusoidal corrugated enclosure with discrete isoflux heating from below

A numerical investigation of the steady magnetoconvection in a sinusoidal corrugated enclosure has been performed. In this analysis, two vertical sinusoidal corrugated walls are maintained at a constant low temperature whereas a constant heat flux source whose length is varied from 20 to 80% of the reference length of the enclosure is discretely embedded at the bottom wall. The Penalty finite element method has been used to solve the governing Navier–Stokes and energy conservation equation of the fluid medium in the enclosure in order to investigate the effect of discrete heat source sizes on heat transfer for different values of Grashof number and Hartmann number. The values of the governing parameters are the Grashof number Gr (10³ to 10⁶), Hartmann number Ha (0 to 100) and Prandtl number Pr (0.71). The present numerical approach is found to be consistent and the solution is obtained in terms of stream functions and isotherm contours.     

Mixed convection in a lid-driven triangular enclosure filled with nanofluids

This paper presents the results of a numerical study on the mixed convection in a lid-driven triangular enclosure filled with a water–Al₂O₃ nanofluid. A comparison study between two different scenarios of upward and downward left sliding walls is presented. The effects of parameters such as Richardson number, solid volume fraction and the direction of the sliding wall motion on the flow and temperature fields as well as the heat transfer rate are examined. The results show that the addition of Al₂O₃ nanoparticles enhances the heat transfer rate for all values of Richardson number and for each direction of the sliding wall motion. However, the downward sliding wall motion results in a stronger flow circulation within the enclosure and hence, a higher heat transfer rate.     

有机包裹体分析方法进展及其问题和思考

随着分析技术的提高,有机包裹体研究作为地球化学的一种手段和方法,已经得到很大的发展。现在的包裹体分析技术在包括用显微镜观测包裹体物理特征、测定包裹体的均一化温度、用色质谱进行FIS研究方法、测定GOI值和分析有机包裹体的分子组成。这些方法主要用于恢复沉积盆地古地温及生油热历史、探讨油气热演化程度和形成阶段、研究古油藏内油气物理化学条件、确定油气运移的相对时间、查明油气运移通道体系和运移方向以及评价油气资源和预测油气勘探远景区等。该文讨论了有机包裹体分析方法的基本原理和分析程序,指出了这些方法存在的问题和解决措施,说明包裹体技术需要在地质的基础上与其它地化分析方法结合才能够更准确地进行研究。     

深基坑无支撑拱圈围护结构的设计与施工——上海银都商城基础施工实践

采用钻孔灌注桩加深层搅拌桩作复合墙体,再加上三道环形混凝土围檩,组成无支撑支护体系。它与矩形对撑体系结合,解决了“L”形状特殊深基坑的围护问题。     

轻型围护门式刚架普通钢结构厂房的优化设计分析

随着轻型围护材料的广泛应用和一些钢结构厂房工程的实践,在普通钢结构厂房中,用实腹式门式刚架代替传统采用的格构式刚架结构成为可能,但现有设计方法只是单纯采用普钢规范和凭借工程经验。为优化这种设计方法,控制用钢量并保证设计的可靠性,通过对我国现行钢结构相关规范、规程的对比分析,结合工程经验,提出了轻型围护门式刚架普通钢结构厂房的优化设计方法。最后用实际工程案例验证了该方法的可行性和优势,为今后同类型的厂房设计提供了一定的设计依据。     

BHP来实轻钢围护系统施工工艺

厦门某工业厂房采用BHP来实轻钢围护系统,屋面无搭接、无螺钉穿透、无压条,防漏可靠,排水能力极佳;并且防热胀冷缩性、隔热、防火、保温、吸声、通风效果好。BHP屋面及墙面的铺装有其特定的工艺和施工要点。在施工中对原设计还进行了部分改进,该厂房至今未出现变形与渗漏现象。