力学学报第7卷1964年目录

第一期薄壳弹塑性理渝的近似舒算·························4·······,··············,··········,············一周承调(1)轴对称载荷作用下旋棘壳的近似屈服条件······················································……曲圣年(12)超高速钝体惴流传热简题····························································……呼和敖德、牛家…     

中国惯性技术学报2006年第14卷总目次

惯性系统研究与分析期页捷联惯导姿态算法的测试输入研究··················································································1 1惯性辅助电光测距技术研究与误差分析·············································································1 7激光陀螺速率偏频系统初始对准方法研究···························…     

中国惯性技术学报2005年第13卷总目次

惯性系统研究与分析期页一种新的惯性导航初始对准滤波方法···············································································1 1惯性平台热场分析及热设计的改进·················································································1 5传递对准中测量延迟的补偿方法·······························…     

力学与实践第9卷(1987年)总目录

中国力学学会第二届理事会工作总结·······························································……钱令希(1 .2)分析力学的近代发展········,··················································……,’’················……梅凤翔(卜10)略谈数学在力学理论研究中的作用····················································…     

固体力学学报1983年总目录

论几种本征值包含定理的内在联系·························································……胡海昌(I一1)两自由度非线性系统的参数共振····························································……余抱青(I一11)复合型断裂的非线性能量分析···················································……沈为李德怡(I一23)土层在其界面受周期孔隙压…     

计算结构力学及其应用第7卷(1990)总目录

第1期计算结构力学、最优控制及偏微分方程半解析法·····,········,··············、·············一~··t··、、一”钟万鳃钟翔翔(1)随机拟协调有限元·······································,························································……陈铁云周义先(lT)样条高斯配点法分析加劲板壳的振动与屈曲问题································…     

力学与实践 第8卷 (1986年) 总目录

海洋工程中的流体力学及数值计算问题····”······················································……顾憋祥(1.3)蒸汽轮机叶片颇振研究·····································································……周盛郑叔珠(1.1羚新型传感器的研制是物理规律和工艺技术相结合的产物·······································……范良藻(2.1)气波增压器研究…     

力学学报1980年分类目录

流体力学旋转大气中运动的适应过程········,················································……曾庆存叶笃正1关于二相渗流的多维问题····························································……陈钟祥袁曾光l轴对称二维定常可压缩流休湍流边界层的计算············“·······················...····……王应时1s:流面的运动方程及其解···········…     

力学与实践第12卷(1990年)总目录

谈谈计算力学的发展············,······,································································……武际可(l·l) 格子气流体动力学及其最新进展·····································································……钱跃软(1 .7) 冷却塔及其流体力学问题···············································…     

爆炸与冲击1987年(第7卷)作者索引

三~五画(马、王、付、白) 马法成“见王诚洪”·····~············“···························”·············~·······~······一l(41)巨区巫」JsG一l型激光速度干涉仪.···”····~·~··················~····“·”·“·”·”·······一(257)· 王士俊螺旋型电流发生器的电感计算·····“···················“····”·······一·······~··……3(2 66)王礼立见“徐天平”··~·…     

Estimation of moisture transport coefficients in porous materials using experimental drying kinetics

From experimental drying kinetics, an inverse technique is used to evaluate the moisture transport coefficients in building hygroscopic porous materials. Based on the macroscopic approach developed by Whitaker, a one-dimensional mathematical model is developed to predict heat and mass transfers in porous material. The parameters identification is made by the minimisation of the square deviation between numerical and experimental values of the surface temperature and the average moisture content. Two parameters of an exponential function describing the liquid phase transfer and one parameter relative to the diffusion of the vapour phase are identified. To ensure the feasibility of the estimation method, it is initially validated with cellular concrete and applied to lime paste.     

A Multiscale Network Model for Simulating Moisture Transfer Properties of Porous Media

A multiscale network model is presented to model unsaturated moisture transfer in hygroscopic capillary-porous materials showing a broad pore-size distribution. Both capillary effects and water sorption phenomena, water vapour and liquid water transfer are considered. The multiscale approach is based on the concept of examining the porous space at different levels of magnification. The conservation of the water vapour permeability of dry material is used as scaling criterion to link the different pore scales. A macroscopic permeability is deduced from the permeabilities calculated at the different levels of magnification. Each level of magnification is modelled using an isotropic nonplanar 2D cross-squared network. The multiscale network simulates the enhancement of water vapour permeability due to capillary condensation, the hysteresis phenomenon between wetting and drying, and the steep increase of moisture permeability at the critical moisture saturation level. The calculated network permeabilities are compared with experimental data for calcium silicate and ceramic brick and a good agreement is observed.     

Nonisothermal moisture transport in hygroscopic building materials: modeling for the determination of moisture transport coefficients

A mathematical model for calculating the nonisothermal moisture transfer in building materials is presented in the article. The coupled heat and moisture transfer problem was modeled. Vapor content and temperature were chosen as principal driving potentials. The coupled equations were solved by an analytical method, which consists of applying the Laplace transform technique and the Transfer Function Method. A new experimental methodology for determining the temperature gradient coefficient for building materials was also proposed. Both the moisture diffusion coefficient and the temperature gradient coefficient for building material were experimentally evaluated. Using the measured moisture transport coefficients, the temperature and vapor content distribution inside building materials were predicted by the new model. The results were compared with experimental data. A good agreement was obtained.     

Modeling of heat and mass transfer in lateritic building envelopes

The aim of the present work is to investigate the behavior of building envelopes made of local lateritic soil bricks subjected to different climatic conditions. The building envelopes studied in this work consist of lateritic soil bricks with incorporation of natural pozzolan or sawdust in order to obtain small thermal conductivity and low-density materials. In order to describe coupled heat and moisture transfer in wet porous materials, the coupled equations were solved by the introduction of diffusion coefficients. A numerical model HMtrans, developed for prediction of heat and moisture transfer in multi-layered building components, was used to simulate the temperature, water content and relative humidity profiles within the building envelopes. The results allow the prediction of the duration of the exposed building walls to the local weather conditions. They show that the durability of building envelopes made of lateritic soil bricks with incorporation of natural pozzolan or sawdust is not strongly affected by the climatic conditions in tropical and equatorial areas.     

Experimental and theoretical studies of convective heat transfer in a cylindrical porous medium

Convective heat transfer at constant heat flux through unconsolidated porous media has been studied both experimentally and theoretically. Heat transfer measurements have been performed for convective heat transfer over a wide range of operational parameters at constant heat fluxes. In addition to heat transfer coefficients, pressure drop and temperature profiles both in radial and axial direction have been recorded. The equations of motion and energy which account for the non-Darcian effect are used to describe the flow and convective heat transfer through the porous medium. Mathematical models for the prediction of heat transfer coefficients and temperature profiles are presented which predict the experimental data with good accuracy.     

Driving Potentials of Heat and Mass Transport in Porous Building Materials: A Comparison Between General Linear,Thermodynamic and Micromechanical Derivation Schemes

In systems of coupled transport processes the question of the appropriate driving potentials is a point of discussion. In this article, three different approaches to derive models for transport currents are systematically compared. According to a general linear approach, an arbitrary full set of independent state variables and material properties is sufficient to describe any transport current. This approach is derived here from a symmetry principle. Thermodynamic and micromechanical approaches are more complex and even less general, but they allow additional statements about the transport coefficients and they reduce the number of transport processes. In the thermodynamic approach the additional information stems from the calculation of the entropy production rate; the micromechanical approach involves a microphysical model of the considered porous system. As a practical example, the three derivation schemes are applied to the often-encountered case of non-hysteretic heat and moisture transport in homogeneous building materials. It is shown, how the general state variables of a porous system are reduced to only two. Then from the general linear approach it can be seen, that all equations for the moisture transport current using a main driving potential (e.g. moisture content, vapour pressure, chemical potential) and an independent secondary driving potential (e.g. temperature, liquid pressure) are equivalent, without recurrence to the thermodynamic or micromechanical approach. However, the transport coefficients are arbitrary phenomenological functions depending on the two state variables. Based on a literature survey it is shown, which additional statements can be made in the thermodynamic and in the micromechanical approach. The latter yields the pressure-driven model (vapour and liquid pressure as the two driving potentials). Finally it is shown, what is to be expected, if in more complex systems the number of state variables increases.     

多孔介质在压力梯度作用下的热质耦合数值模拟

多孔介质干燥导致热质耦合传输过程。本文基于连续介质力学的宏观尺度,对多孔介质的热、湿和气三者耦合迁移进行数值模拟,研究压力梯度对热质传输的影响。多孔介质传质机理主要为水汽和空气的对流和扩散传输、吸附水在含湿量梯度作用下的自由扩散和其在温度梯度即Soret效应驱动下的流动。采用Galerkin加权余量的有限元方法,提出了...     

Heat and mass transfer in unsaturated porous media with solid–liquid change

 A model on heat and mass transfer in unsaturated porous media with solid/liquid phase change was developed with extending the three-variable model previously proposed. The movement of air phase and its effect on the motion of water is considered. The model has been checked with comparison of the experimental results of the temperature distribution for two dimensional freezing process. The evolution of air pressure, water and ice saturation were predicted by solving the governing equations. The ice segregation and moisture movement toward the front of freezing were numerically simulated. Received on 8 December 1999     

An Air Permeability Study of Anisotropic Glass Wool Fibrous Products

This article reports an experimental study of the permeability of fibrous porous media based on air flow. Two glass wools have been analyzed in three different flow directions to evaluate their anisotropic structure. The usual flow theories such as Darcy’s law, valid for granular materials, have been shown to apply also to these fibrous media which is a more complex structure (fiber arrangement, high porous media,…). The intrinsic permeabilities and the anisotropic factors have been determined from an air permeability measurement based on a standard test for industrial fabrics. The experimental results have been compared to different models, showing the limits of some simplistic models when applied to our highly porous structures. One model, Kyan’s model based on the flow around submerged objects, was, however, found to agree with our experimental data. This study also demonstrates the interesting use of an experimental technique, which is air permeability measurement (water permeability is not adapted), in the investigation of flow phenomena in a fibrous medium.     

Multiphase transfer model for intermittent microwave-convective drying of food: Considering shrinkage and pore evolution

Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves both energy efficiency and food quality during drying. Although many experimental studies on IMCD have been conducted, there is no complete multiphase porous media model describing the physics of the process available in the literature. A multiphase porous media model considering liquid water, gases and the solid matrix of food during drying can provide in-depth understanding of IMCD process. Currently there is no IMCD model that have taken shrinkage and pore evolution during drying into consideration. In this study, first a multiphase porous media model with shrinkage (IMCD2) has been developed for IMCD. Then the model has been compared with IMCD model without shrinkage (IMCD1). Simulated temperature, moisture content, density, porosity from IMCD2 are then validated against experimental data. The profile of vapour pressures and evaporation during IMCD are also presented and discussed.