多孔纤维织物热湿传递数值模拟的研究进展

热湿传递数值模拟的研究可为多孔纤维织物的制备和热湿性能评估提供理论基础。在阐述了织物热湿传递机制的基础上,从织物热湿传递数值模型、数值模拟计算方法以及织物热湿传递性能测试方法 3个方面,综述了近年来关于织物热湿传递方面的新进展,分析了现有织物传热传湿数值模拟研究中存在的问题,提出在创建织物三维方向上的热湿耦合模型时,要综合考虑织物本身的交织结构特征和纱线的物理性能;在数值分析过程中要充分考虑实际应用条件下织物材料物理性能的变化,进一步优化织物传热传湿数值模型,提高模拟计算的准确度。     

考虑内部辐射下织物热湿传递现象的数值研究

人体在着装情况下的热湿传递现象对人体的热舒适性的研究有着很重要的地位。考虑了由于温度差而引起的织物内部的辐射热传递，对织物中的热湿传递现象进行了数值研究，建立了考虑辐射现象下织物内部热湿传递的简单模型，并讨论了计算结果。     

A mathematical model for simulating heat and moisture transfer within porous cotton fabric drying inside the domestic air-vented drum dryer

A mathematical model was developed to describe the processes of coupled heat and mass and momentum transfer occurring in convective drying of 100% porous cotton fabric. In this model, the variation in both air and fabric properties were expressed as a function of temperature and moisture content. The resulting systems of transient non-linear partial differential equations in the space-time domain together with the set of initial values and boundary conditions were numerically solved by utilizing the finite difference method. A series of laboratory drying experiments were performed using a computer-controlled dehydration system, which was developed to obtain data of drying kinetics under varying operating conditions for the validation of the predicted results from the proposed model. The experimental results has shown a very good agreement with the predictions of the model, which indicates that the proposed numerical model can be used with confidence as a tool in optimizing the design and operation of the fabric drying system. A parametric study was performed using the modeling tool has demonstrated the impact of key operational parameters on the drying kinetics, which has significant meaning on improving fabric’s appearance smoothness and decreasing the damage. It is expected that the model can be applied for other fiber products and processes involving similar phenomena.     

基于Luikov理论的烟丝贮丝过程热湿特性研究

通过对烟草热湿传递机理的分析,基于Luikov理论,建立了烟丝贮丝过程热湿传递方程,并利用量纲分析和Laplace转换对方程求解,得到烟丝堆积床温度场和湿含量分布的解析解,其结论为深入研究贮丝过程热湿迁移规律提供了理论依据.     

人体着装传热传质过程的数学模型(二)--模型的数值求解

对人体着装传热传质过程的数学模型进行了三维离散，并利用完全隐式差分格式和MATLAB软件进行了数值求解，得到了较为满意的结果。通过与实验结果的比较，验证了模型的正确性，为利用计算机技术对人体热湿舒适性的仿真分析奠定了基础。     

人体着装传热传质过程的数学模型(一)--模型方程

基于液汽两相流质量、动量、热量守恒方程组及表征性体积单元的概念,考虑到人体-服装-环境这一体系中的对流、扩散、蒸发、毛细运动、吸附等现象,建立了人体着装传热传质过程的数学模型,得到了较为满意的结果,为利用计算机技术对此进行数值分析和模拟奠定了基础。     

The application of computational fluid dynamics codes to simulate heat and moisture transfer in stored grains

An aim of stored-grains technologists has been to develop robust and flexible mathematical analyses of the heat and moisture transfer phenomena that occur in bulks of stored grains. A requirement has been that the models are able to simulate the wide range of storage geometries and operating conditions that occur in practice. Software packages developed from the discipline of computational fluid dynamics offer these possibilities. Such packages can be used to attack an extremely wide range of problems by solving the equations that govern the conservation of heat, mass and momentum. However, they need to be customised if they are to calculate velocity, temperature and moisture distributions in bulk stored grains. This paper demonstrates how these modifications can be made and how the results can be portrayed graphically in a way that permits insights into the processes that occur in grain stores.     

3D modelling of coupled mass and heat transfer of a convection-oven roasting process

A 3D mathematical model of coupled heat and mass transfer describing oven roasting of meat has been developed from first principles. The proposed mechanism for the mass transfer of water is modified and based on a critical literature review of the effect of heat on meat. The model equations are based on a conservation of mass and energy, coupled through Darcy's equations of porous media — the water flow is mainly pressure-driven. The developed model together with theoretical and experimental assessments were used to explain the heat and water transport and the effect of the change in microstructure (permeability, water binding capacity and elastic modulus) that occur during the meat roasting process. The developed coupled partial differential equations were solved by using COMSOL Multiphysics®3.5 and state variables are predicted as functions of both position and time. The proposed mechanism was partially validated by experiments in a convection oven where temperatures were measured online.     

Mathematical modeling of the heat and mass transfer in a stationary potato sphere impinged by a single round liquid jet in a hydrofluidization system

The hydrofluidization (HF) is a method of chilling and freezing of foods which consists in a circulating system that pumps a refrigerating liquid upwards through orifices or nozzles, creating agitating jets. The objectives of this work were to develop a mathematical model to represent the combined heat and mass transfer between a food and a refrigerant liquid medium in a HF system and to validate the model using a single stationary sphere of food impinged by a single round jet of liquid. The food domain consisted of a rigid solid matrix, a liquid phase and the ice phase. Transport equations were applied to each phase and solved by a control-volume approach. The transport phenomena in the fluid domain were studied by computational fluid dynamics. The surface heat transfer coefficients obtained from fluid flow simulations were used to model the heat and mass transfer inside the food. Experimental central temperature and average solute uptake profiles were obtained when potato spheres were placed in a HF system using a NaCl-water as refrigerant and considering different temperatures (−10 and −15 °C), flow rates (1 and 3 L min⁻¹), and orifice-sphere distances (1 and 5 cm). The predicted values agreed well with the experimental ones, the maximum root mean square errors being 3.3 g NaCl kg⁻¹ potato and 2.9 K for the average solute concentration and temperature profiles studied, respectively. The simulations improved the understanding of the HF process and it may help to study and control different operation scenarios.     

Immersion chilling and freezing of a porous medium

An experimental apparatus, putting one face of a water-saturated glass bead bed in contact with a high-concentration (23% NaCl) aqueous freezant (the other face being insulated against heat and mass transfer), was constructed to simultaneous study heat and mass transfer at the product/solution interface and within the product more closely than is possible in real foods. The selected flow allowed uniform heat treatment (a constant heat transfer coefficient) over a large part of the product. The apparatus was used to monitor three elements within the product: the temperature profiles, the NaCl concentration profiles for the liquid phase and the freezing and thawing fronts. The first results showed that a surface layer of a highly impregnated non-frozen product was present at the end of freezing. If the frozen product was left in contact with the refrigerating solution, progressive thawing occurred from the surface inwards; thawed layer thickness seemed to be a linear function of the square root of time.     

A method for the calculation of the heat transfer coefficient in potato drying

A method for the determination of the heat transfer coefficient was proposed for the first falling drying period of potato cubes. During this period, heat and mass transfer were considered as coupled phenomena. Temperature calculation inside the sample was performed using the macroscopic heat transfer balance. The heat transfer coefficient was computed by means of parametric identification, using the Gauss–Newton method. The figure obtained for the heat transfer coefficient shows good agreement with other sources.     

改性聚丙烯酸类纤维吸湿发热机织物的开发

为研究吸湿发热保暖机织物的热湿舒适性,开发了6种不同结构的改性聚丙烯酸类纤维吸湿发热机织物。通过热湿舒适相关性能测试与分析,得出不同机织物结构参数对透气性、热阻、芯吸高度、液态水分管理以及吸湿发热性能的影响规律,为设计出兼具吸湿发热和导湿排汗性能的热湿舒适机织物提供参考。经测试发现:蜂巢组织能明显改善织物的保暖性和透气性,且织物由内层向外层形成回潮率递增的梯度结构,对水分管理和提高单向导湿性能有积极作用,三层蜂巢组织在提升织物吸湿发热性能上具有一定潜力。     

改性聚丙烯酸类纤维吸湿发热机织物的开发

为研究吸湿发热保暖机织物的热湿舒适性,开发了6种不同结构的改性聚丙烯酸类纤维吸湿发热机织物。通过热湿舒适相关性能测试与分析,得出不同机织物结构参数对透气性、热阻、芯吸高度、液态水分管理以及吸湿发热性能的影响规律,为设计出兼具吸湿发热和导湿排汗性能的热湿舒适机织物提供参考。经测试发现:蜂巢组织能明显改善织物的保暖性和透气性,且织物由内层向外层形成回潮率递增的梯度结构,对水分管理和提高单向导湿性能有积极作用,三层蜂巢组织在提升织物吸湿发热性能上具有一定潜力。     

用统一建模语言实现中小型粮库管理系统建模设计

通过对中小型粮库管理系统的层次分析,采用统一建模语言(UML)实现对中小型粮库管理系统的建模设计,以期为中小型粮库实现数字化信息系统提供依据.     

Heat and Moisture Transfer in Composite Food—Theoretical Analysis of Influence of Surface Conductance and Component Arrangement

Heat and moisture transfer in composite bodies undergoing drying was simulated using a previously developed mathematical model which included the chemical potential of moisture as a mass transfer potential. Composite bodies included layered cylinders and concentric spheres consisting of a starch granule hydrate (H) and a hydrate of starch granules-sucrose 3:l mixture (S). The influence of the following factors on heat and moisture transfer was examined: convective surface mass transfer conductance, initial moisture, and component arrangement. The three factors significantly influenced moisture transfer white they had slight influence on heat transfer. Overall drying rate of each composite body was infhrenced interactively by moisture fluxes, which were caused by a surrounding drying medium and by a mass transfer potential difference across the interface of H and S.     

纺织纹样在楚凤文创产品包装设计中的应用

将纺织纹样应用到楚凤文创产品包装设计中,对设计水平的提高较为有利。就该类型纹样的应用方法进行了研究,介绍了文创产品包装的设计要点及分类;从元素、形式以及色彩3个方面出发,总结了纹样设计的构成要素;重点针对不同要素在楚凤文创产品包装设计中的应用方法进行研究,希望能够为有关人员提供参考。     

X型开缝翅片传热与流动性能的数值模拟

对X型开缝翅片的流动与传热性能进行数值模拟,并把计算结果与平片和开缝翅片的计算结果进行比较.结果表明:从3种开缝翅片的JF因子看,X型开缝翅片的最大,说明其性能最优.2种X型开缝翅片管的尾迹区较小,因此该种结构能有效减小尾迹区对换热的影响.     

喷水室热、质传递的理论分析

以水滴在喷水室中的受力情况为出发点，借助于相对运动理论，建立了数学模型。得出了水滴运动过程中的速度分布函数及水滴在喷水室中参与热质交换的时间，进而得出了顺喷情况下喷水室热交换效率系数。并分析了各因素对水-空气处理系统全热交通性能的影响，对实际问题有一定指导意义。     

CFD modeling of heat transfer and flow field in a bakery pilot oven

A bakery pilot oven is modeled using computational fluid dynamics software. This approach relies on integration of an instrument into modeled geometry. The instrument is a heat flux measuring device that can be used in the industrial baking process. All three heat transfer mechanisms are considered and coupled with turbulent flow. Turbulence is taken into account via the k–ε realizable model whereas the surface-to-surface model simulates the radiation. Additionally, buoyancy forces are introduced by means of a weakly compressible formulation. The model predictions show a good qualitative agreement with the experimental measurements. A quantitative agreement was obtained to some extent. Limitations came from the difficulty to measure the temperature of the radiant surfaces of the oven. Operating conditions used are typical of bakery products and, as expected, radiation was the dominant mode of heat transfer. The integration of the instrument was useful for assessing the model. Since it is designed for industrial use, it may be a valuable tool for future challenges in the field, such as simulation of an industrial scale oven.     

Mathematical modeling of the heat transfer process and protein denaturation during the thermal treatment of Patagonian marine crabs

Southern Ocean swimming crab Ovalipes trimaculatus and the Patagonian stone crab Platyxanthus patagonicus are fishing resources with commercial value. Thermal treatment of crabs is necessary to denature muscle proteins, facilitating meat detachment from the crab shell (picking procedure). The proximal composition, protein patterns of crab muscle, thermophysical properties and heat transfer coefficients were determined. Heat transfer during thermal processing of body (i.e., cephalothorax) and claws of both crab species was simulated using a finite element computational code; the simulations were experimentally validated. Color changes in crab muscle during the heating process were measured. Thermal denaturation kinetics of myofibrillar proteins was determined using Differential Scanning Calorimetry (DSC) in small samples previously heated in water under controlled conditions. DSC thermograms of raw crab muscle showed two peaks at 49.0 ± 0.4 and 77.5 ± 0.6 °C corresponding to myosin and actin respectively. Activation energies for the denaturation of myosin (145.70 kJ/mol) and actin (156.42 kJ/mol) were calculated from Arrhenius equation. The degree of denaturation achieved by the myofibrillar proteins at the coldest point of the muscle in body and claws during the heating process was established by considering the protein denaturation kinetics determined by DSC, the activation energies and the heat penetration curves. Adequate conditions for the detachment of meat from the crab exoskeleton were established. The obtained results may help in determining the optimal heating times during the industrialization of these crustaceans.