Heat and Mass Transfer in Anisotropic Bodies

This review is aimed, on the one hand, at attracting the researchers' attention to the problems associated with heat transfer in anisotropic bodies and, on the other hand, at analyzing the scanty experience in investigating the heat transfer in anisotropic bodies that has been accumulated over the last 30 years. We treat conjugate heat transfer between boundary layers and anisotropic bodies, and heat transfer under conditions of simultaneous reciprocal influence of anisotropic thermal conductivity and anisotropic filtration upon film cooling of bodies with anisotropic properties. New effects are revealed during simulation of conjugate heat transfer; the law of nonlinear filtration in anisotropic bodies is identified; and the effect of individual components and of the orientation of the principal axes of thermal conductivity and penetrability tensors on stationary temperature fields and on the distribution of components of the filtration rate is investigated. The results of analytical investigation of heat transfer in anisotropic bodies enables one, under conditions of lack of adequate information, to exactly simulate nonstationary temperature in simplest anisotropic bodies, which may be used as test results. A number of recommendations are formulated for implementation of heat shielding of anisotropic bodies under conditions of their aerogasdynamic heating.     

Parabolized Viscous Shock Layer in View of Conjugate Heat Transfer

The model of a parabolized viscous shock layer is used to solve the problem of descent of a smooth blunt body possessing a lift-to-drag ratio and a heat-conducting surface in a sliding path in Earth's atmosphere.     

Analytical and Experimental Investigations on the Heat Transfer Properties of Light Concrete

It is well known that the thermal performance of some insulating and building materials is related to the actual operating conditions because the thermal conductivity of such materials is highly dependent on the moisture content. Since the thermal conductivity of liquid water is about 25 times greater than that of air, it is quite easy to understand how even small variations of the moisture content can have a significant impact on thermal performance. For this reason it is important to find a correlation between the moisture content in a specimen and its thermal conductivity. The purpose of this paper is to investigate both experimentally and theoretically the moisture contribution during the measurement of the heat transfer properties in light concrete slabs (autoclaved concrete and concrete lighted with polystyrene pearls) and to correlate its thermal transmissivity with the moisture content.     

各向异性介质二维稳态热传导问题的分析解

本文利用双变量函数及其偏导数在闭区间上完整的双重付里叶级数表达式求得矩形区域中各向异性介质稳态热传导问题的分析解。文中例子给出各向异性介质内的温度场和热流密度的数字结果,并讨论介质的各向异性效应。     

Method of Characteristics for Anisotropic Bodies with a Finite Velocity of Propagation of Heat

The equation of propagation of the characteristic surfaces in anisotropic continuous media with a finite time of relaxation of the heat flux is obtained.     

Analytical Solutions to Models of Local Nonequilibrium Heat Transfer

High Temperature - A series of boundary-value problems of local nonequilibrium heat transfer is considered in terms of the theory of transient heat conduction for hyperbolic-type equations (wave...     

Healing of Cracks in Anisotropic Bodies

Materials Science - We obtain the solution of a plane problem of the theory of elasticity on the phenomenon of “healing” of a crack in an anisotropic body. By using the model of...     

中温热管换热器内传热特性的研究

采用有效度-传热单元数(ε-NTU)法,建立了中温热管换热器的离散型数学模型。研究了中温热管换热器冷侧和热侧的传热特性。建立了单根热管的传热模型来修正计算热管热阻时所产生的温度误差,分析了单根热管的传热过程对整个换热器换热的影响。研究成果为安全衔接热管不同温度区域内的每排热管和强化中温热管换热器的传热性能以及中温热管换热器的进一步结构优化提供了理论依据。     

Healing of Shear Cracks in Anisotropic Bodies

Materials Science - We solve the plane problem of the theory of elasticity of anisotropic bodies with transverse shear cracks “healed” by the injection technologies, which is reduced to...     

Boundaries of Regimes with Improved Heat Transfer at a Supercritical Pressure of Organic Coolants

Based on experimental data on the heat transfer of organic coolants, the authors developed an empirical equation for determining the boundary of occurrence of the stable regime of improved heat exchange.     

藕状多孔铜微通道热沉的散热性能优化研究

藕状多孔铜是一种具有长直圆孔的新型微通道结构,可用于对大功率电子器件进行散热。通过实验和Flow Simulation数值计算系统地研究了以水为工质,具有均匀微槽道结构的多孔铜热沉的散热性能。实验结果表明,该热沉具有很高的换热系数,在110 m L/s流量下,换热系数可达10.1 W/(cm~2·K)。模拟结果表明存在最佳的微槽道数和微槽道方向使得多孔铜热沉的散热性能最优。以水为工质时,最佳槽道数和微槽道方向分别为7~11和45°。随着微槽道宽度减小,热沉散热性能提高,对比了数值模拟结果与实验结果,并分析了其存在差异的原因。     

相变窗传热特性实验研究

本文采用熔融共混法制备十四酸(MA)-十六醇(HD)二元有机复合相变材料,利用差示扫描量热仪(DSC)确定了复合相变材料的相变温度和相变潜热。相变温度为35.5℃,相变潜热为218.23 kJ/kg,经过300次热循环实验,结晶温度变化在0.2℃以内,热稳定性良好。利用高低温交变试验箱模拟夏季室外温度变化(变化范围18~58℃),测试了双层窗与相变窗内外表面温度随环境温度的变化特性。结果表明:相变窗外表面温度峰值较双层窗降低5.9℃,相变窗内表面温度峰值较普通双层窗降低0.6℃,温度持续稳定100 min,整个测试过程中相变窗控温效果明显。相变窗较双层窗具有良好的负荷转移能力。     

Crack Healing under Antiplane Deformation of Anisotropic Bodies

Strength of Materials - A mathematical model of longitudinal shear crack healing in an anisotropic body was constructed. The problem was reduced to the solution of the singular integro-differential...     

翅片管式换热器换热与压降特性的实验研究进展--实验研究

概述目前国内外空调制冷行业中普遍采用的几种不同翅片类型(平直翅片、波纹形、条缝形翅片、百叶窗形翅片)的换热特性和压降特性的实验研究进展,通过对这几种翅片类型换热及压降特性的介绍和分析,提出了趣片管式换热器研究中的一些不足。     

The Simplified Analytical Models for Evaluating the Heat Transfer Performance of High-Porosity Metal Foams

The accurate evaluation of the specific surface area and the effective thermal conductivity (ETC) of high-porosity metal foams is an important prerequisite to study the mechanism of heat transfer enhancement. In this paper, the tetrakaidecahedron, concave triangular prism and equivalent tetrahedron were used to develop the geometry shapes of cell, ligament and node, respectively. The calculation model of the specific surface area characterized by porosity and pore density (PPI) was deduced by considering the shape characteristics. Based on the angle between the two-dimensional plane skeleton layer and the heat flow direction, the ETC analytical calculation model characterized by only the porosity in the three-dimensional space was deduced. Without any other fitting or experimental empirical parameters, these two models are only related to porosity and PPI, which are the most readily available parameters for the metal foams. The results of these models are consistent with the experimental and empirical data in other literature, indicating that these models are both versatile and accurate.