On combination of first order Strang's splitting and additive splitting for the solution of multi-dimensional convection diffusion problem

In this article we present a new splitting approach for the numerical solution of the multi-dimensional convection diffusion equations. The method combines additive and multiplicative splitting. In particular the method combines first order Strang's splitting, multiplicative splitting defined for splitting the convection and diffusion equation, and additive splitting defined in accordance with the spatial variables. The method not only reduces the linear (or nonlinear) original problem into a series of one-dimensional and one physical operator linear problems, but also enables us to compute these one-dimensional problems using parallel processors. The accuracy and stability of the new algorithm are investigated through the solution of different multi-dimensional convection diffusion model problems with scalar coefficients.     

Identification of diffusion parameters in a non-linear convection–diffusion equation using adaptive homotopy perturbation method

This paper is concerned with the numerical identification of diffusion parameters in a non-linear convection–diffusion equation, which arises as the saturation equation in the fractional flow formulation of the two-phase porous media flow equations. In order to overcome the defect of the local convergence of traditional methods, an adaptive homotopy perturbation method is applied to solve this parameter identification inverse problem. The adaptive homotopy perturbation method provides a simple way to adapt computational refinement to the choice of the homotopy parameter. Numerical simulations illustrate that the proposed algorithm is globally convergent and computationallyefficient.     

Phase-change heat transfer of single/hybrid nanoparticles-enhanced phase-change materials over a heated horizontal cylinder confined in a square cavity

The melting process of a nano-enhanced phase-change material is investigated in a square cavity with a hot cylinder located in the middle of the cavity in the presence of both single and hybrid nanoparticles. The dimensionless partial differential equations are solved numerically using the Galerkin finite element method using a grid with 6000 quadrilateral elements. The effects of the volume fraction of nanoparticles, the Fourier number, the thermal conductivity parameter, and the viscosity parameters are studied. The results show that the solid-liquid interface and the liquid fraction are significantly affected by the volume fraction of nanoparticles and the thermal conductivity parameter. Additionally, it is found that the melting rate is much larger when the Fourier number changes between 0 and 0.5 and a further increase in the Fourier number causes a reduction in the rate of the melting.     

Transport phenomena in the electrodeionization of cesium from AMP-PAN

Electrodeionization (EDI) of cesium from cesium-sorbed ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) was investigated by passing eluant through the packed bed of ion-exchange resin in an electrodialysis cell. The deionized cesium from the packed bed was recovered in catholyte by migration and in the eluant by convection. Recovery percentage of Cs by migration increased while the recovery by convection decreased with increase in current density from 20 to 40 mA/cm². Increased eluant concentration resulted in low migration percentage of cesium. Increased catholyte concentration had a negligible effect on total recovery. Apparent diffusion coefficients evaluated using the Nernst–Plank relation increased with increase in current density and catholyte concentration while a decreasing trend was observed with increase in eluant concentration.     

寒冷和严寒地区建筑门窗节能设计和解决方案（一）

本文以寒冷和严寒地区建筑门窗的节能保温为主线,对现行国家标准进行了介绍,指出了影响门窗节能保温的五大因素,对门窗的节能设计和解决方案进行了阐述,可供在实际工作中应用。     

Thermal management of lithium‐ion batteries for electric vehicles

Thermal issues associated with electric vehicle battery packs can significantly affect performance and life cycle. Fundamental heat transfer principles and performance characteristics of commercial lithium‐ion battery are used to predict the temperature distributions in a typical battery pack under a range of discharge conditions. Various cooling strategies are implemented to examine the relationship between battery thermal behavior and design parameters. By studying the effect of cooling conditions and pack configuration on battery temperature, information is obtained as to how to maintain operating temperature by designing proper battery configuration and choosing proper cooling systems. It was found that a cooling strategy based on distributed forced convection is an efficient, cost‐effective method which can provide uniform temperature and voltage distributions within the battery pack at various discharge rates. Copyright © 2012 John Wiley & Sons, Ltd.     

Fully developed thermal behaviors for parallel flow microchannel heat exchanger

The hydrodynamics and thermal behaviors of the flow in micro-heat exchanger parallel-plate are investigated numerically. The model that combines both the continuum approach and the possibility of slip at the boundary is adopted in the study. Effects of different parameters, such as, Knudsen number (Kn), heat capacity ratio (Cr), the effectiveness (e) and number of transfer units (NTU) are investigated. It is found that both the velocity slip and the temperature jump at the walls increase with increasing Kn. On the other hand, at low values of Kn, the NTU increases with increasing Cr, but at high values of Kn the NTU decreases with increasing Cr. With regard to the effect of Cr on e, it is found that increasing Cr leads to a reduction in e and for all Kn.     

基于深对流云的夜间微光传感器定标技术

NPP(National Polar-orbiting Parternership)卫星于2011年10月28日发射升空,其上搭载的VIIRS(Visible Infrared Imaging Radiometer Suite)传感器包含DNB(Day Night Band)波段,该波段采用三增益设置,可在白天、晨昏甚至夜间实现地球观测.其中,在夜间月光条件下,主要采用高增益,定标实现较为困难.以此为目的,首次提出了基于深对流云的夜间微光传感器替代定标方法.将月亮辐射模型引入到SCIATRAN中,实现了全天候的辐射传输计算,并利用该改进的辐射传输模式,通过确定深对流云光学属性、地表特性及大气廓线等的参考值,对接收大气层顶反射辐射进行敏感性试验,分析得到主要影响因子为云光学厚度COT(Cloud Optical Thickness)与有效粒子半径Re(Effective Radius),且利用固定参考值得到最大模拟误差小于5%.为了检验该替代方法的可行性,通过改进的辐射传输模式,对2012年08月~2013年01月共6个月夜间DNB数据所确定的深对流云替代目标像素进行辐射传输模拟,结果表明基于深对流云的替代定标方法效果较好,基于日变化的辐射不确定度在±10%之内,可实现对DNB夜间高增益阶段的直接辐射定标.     

敏感工作气体对射流陀螺灵敏度的影响

研究了干燥空气、N2和He等3种常用敏感工作气体对射流陀螺灵敏度的影响。采用有限元法计算了输入角速度ωi=20(°)/s时敏感元件内的流场。计算结果和实验表明,改变敏感元件内敏感工作气体的种类,流场分布也随之变化。ωi=20(°)/s时,两热电阻丝r1、r2处的气流速度差ΔvN2>ΔvAIR>ΔvHe。灵敏度系数KN2>KAIR>KHe,其中KN2=1.05 KAIR,KHe=0.21%KAIR。N2对应的灵敏度最高,热电阻丝抗氧化,稳定性较好,但成本高;干燥空气的灵敏度次之,热电阻丝易氧化,稳定性差;He对应的灵敏度最小,热电阻丝不易氧化,稳定性最好。该文解释了敏感工作气体对射流陀螺灵敏度的影响机理,为提高射流陀螺的实用性,满足不同工程需要开辟了一个新的途径。     

Convective heat transfer in domed skylight cavities

Domed skylights are important architectural design elements that deliver daylight and solar heat into buildings, and connect the building's occupants to the outdoor environment. Despite the widespread use of domed skylights, there is limited information on the convective heat transfer within cavities of multi-glazed domes. This information is required to evaluate the thermal performance of domed skylights for product rating purposes, or to evaluate the heat loss or gain of installed skylights in buildings. This article presents a numerical study on the laminar natural convection in horizontal concentric domed cavities heated from the inside surface. A commercial CFD package is used to solve for the flow and temperature fields. The results show that for large cavity gap spacing-to-radius ratios, the cavity flow is mono-cellular and steady state. For small gap spacing ratios, however, the cavity flow may be multi-cellular and transient periodic. Practical correlations for the heat transfer coefficient as a function of the cavity shape and gap spacing ratio are developed for both flow regimes. The critical gap spacing ratio that yields the maximum Nusselt number is quantified for each cavity shape.