Finite Element Analysis of Moisture Diffusion in Stored Foods

A Finite Element model was used to predict the average moisture content of foods represented by axisymmetric shapes. The model was found to adequately predict the moisture content for the majority of the foods represented by cereal, dairy, fruit, vegetable, meat and semi-moist bakery food groups. For two foods, flour desorbing to 0.11 a_w and turnips adsorbing to 0.75 a_w, the predictions lmproved when variable diffusivity was used as contrasted with constant diffusivity. The Finite Element model was tested for different foods with different size, shape and diffusion potential.     

Modelling Thermal Conductivity in Heterogeneous Media with the Finite Element Method

Three-dimensional finite element simulations were developed to predict the effective thermal conductivity of theoretical composite materials having complex structures. The models simulated a steady-state thermal conductivity measurement device performing measurements on theoretical materials with varying structures. The structure of a composite was considered to be composed of some simplified basic models. When the geometry, orientation type and number of dispersion are specified, the computer randomly generated the position and orientation for each dispersion and created the geometrical model and finite element mesh. The effective thermal conductivity of the theoretical composite was calculated using this method and compared to the values obtained by simple effective thermal conductivity models methods. The influence of some factors such as the volume fraction and the ratio of the thermal conductivities of the heterogeneities and the surrounding material on the effective thermal conductivity is discussed.     

基于有限元的热裂法切割液晶玻璃的仿真分析

介绍了激光热裂法,即利用移动热源控制裂纹切割玻璃.运用有限元软件Ansys的参数化设计语言建立二维模型,对激光扫描玻璃模型进行仿真.通过该仿真研究了切割过程中裂纹尖端附近的应力和裂纹尖端的应力强度因子,讨论了激光功率和激光扫描速度两关键加工参数对切割的影响,并给出了裂纹可连续扩展的加工参数范围.仿真结果表明,以裂纹尖端...     

第六讲空间问题的有限元方法

前面几讲我们介绍了平面问题的有限元分析方法及其原理,关于空间问题的有限元分析这里只介绍工程上常见的空间梁单元和轴对称问题.     

A Manual Method for Predicting Nutrient Retention During Thermal Processing of Conduction-Heating Foods in Rectangular Containers

The objective of this research work was to develop and evaluate simple manual procedure for the prediction of the retention of nutrients with first order kinetics of thermal degradation, during thermal processing of conduction-heating foods packed in rectangular containers. An equation was developed that permits the estimation of the integrated nutrient retention over the volume by means of Stumbo's formula method. The procedure was compared with literature data for thiamin retention in various thermal processes. Results obtained from the application of the method were within the 90% confidence interval of the experimental values.     

基于多物理场有限元法的热铆结构设计与优化

基于多物理场有限元分析方法对热铆结构进行了电-热-结构的耦合分析。首先研究了热铆结构的材料选型,发现金属压头采用黄铜比采用不锈钢,其表面温度高10℃左右;塑料护套采用PTFE比采用PA6,其表面温度低15℃左右。为此,考虑黄铜金属压头和PTFE塑料护套的组合,进一步进行了热铆结构的尺寸优化,优化后热铆结构成本大大下降,热效率大幅提高,并能满足强度要求。     

第七讲动力学问题的有限元方法

动力学问题是一个带普遍性的问题,工程机构或结构系统的设计和开发离不开系统的动力学特性的分析,这是控制系统设计的基础和前提.由于动力学模型的高阶和非线性以及耦合问题的存在,解决动力学问题一般情况下都是采用数值解法,有限元分析不失为一种有效的具有较高精度的数值方法.这一节主要介绍采用有限元方法求解动力学问题的基本原理和步骤,讨论如何建立弹性结构的离散化运动微分方程、包括质量矩阵和阻尼矩阵的形成,讨论运动微分方程求解的直接积分法和振型叠加法.动力学分析中除了有限元本身的特点外,更多地存在数学问题,因此,更加深入的研究请读者参考有关文献资料.     

Thermal Conductivity of Liquid Foods by the Thermal Comparator Method

The thermal comparator is shown to be a rapid, accurate method for determining the thermal conductivity of liquid foods. Increasing solids content decreased thermal conductivity for apple juice concentrate, orange juice concentrate, and milk samples. Equations for predicting the thermal conductivity of apple juice, orange juice, and milk are shown to be specific for each commodity. A comparison of apple juice and orange juice suggests that qualitative attributes of the solids fraction as well as the quantity present are important in determining thermal conductivity.     

Thermal Analysis of the Freezing of Ice Cream Brickettes by the Finite Element Method

An unsteady-state theoretical analysis of the cooling of a large cross-section ice cream brickette is presented, to model the hardening process required for handling and storage purposes. The material physical properties, i.e. heat conductivity and thermal capacity, are considered temperature dependent, according to available experimental data on a vanilla ice cream. The material is assumed to be macroscopically homogeneous, in the sense that the phase change is simulated by adoption of effective physical properties. The bidimensional differential equations governing the process have been solved numerically using the finite element method, which is extremely powerful for defining optimal design criteria and process control strategies. Results are presented and discussed for different external heat transfer conditions.     

关于细长扩展梁问题的有限元法

分析了奇异摄动两点边值细长扩展梁问题的一种有限元方法 ,并获得了收敛定理 .     

Finite Element Modeling of Moisture Transfer During Storage of Mixed Multicomponent Dried Foods

A finite element model is described that can be used for predicting moisture transfer in mixed food products during storage. Two of three components (raisins, roasted peanuts, banana chips, and roasted almonds) were packed in a well sealed cup. The rate of moisture transfer between the components was assumed to be limited by the component with the Lowest effective diffusion coefficient divided by the square of half of smallest dimension (i.e., D_effLo²) value. The surface moisture content of the rate determining component was assumed to be in equilibrium with the other component(s) at all times. The mean error between the experimental and predicted moisture values with time ranged from 0.28% to 0.84% as a percentage of moisture content.     

Acrylamide Formation in Foods during Thermal Processing with a Focus on Frying

This paper summarizes the current state of knowledge on acrylamide formation in foods during thermal processing. The main pathway of acrylamide formation in foods is linked to the Maillard reaction, and in particular, the amino acid asparagine. Effects of several factors related to food composition and processing conditions on the formation levels of acrylamide, and also, other quality characteristics in thermally processed foods are discussed in detail. From a process control point of view, it is also addressed that there is a need to develop viable models for the estimation of acrylamide contents in heated foods during the stages of process design and optimization. Fried potato products, as one of the most encountered category of thermally processed foods, are specifically emphasized for acrylamide formation, potential ways of mitigation, and modeling its formation during frying.     

用鲜木瓜加工方便食品的工艺研究

应用真空糖渍和真空低温干燥技术对新鲜木瓜进行加工,研制具有天然水果色、香、味的木瓜方便食品.该产品色泽鲜亮透明,果片饱满,酸甜适中,味道鲜美,具有浓郁的典型的木瓜风味,且含有大量的Vc等营养物质和独特的保健功能.     

织物悬垂特性的有限元计算分析

通过对织物基本力学行为的描述 ,运用几何非线性有限元方法对织物在悬垂时发生的大位移、大旋转、小应变的特殊力学现象进行了分析计算。试验表明 ,计算结果与实际情况吻合较好。     

基于Marc的金属塑性加工有限元模拟

介绍了金属塑性加工有限元模拟分析的目标和方法。结合实例,论述了利用有限元分析软件M SC.M arc实现塑性加工过程数值模拟分析的方法和步骤,并以模拟分析的结果指导生产实际,提高塑性加工行业的科学化水平。     

Sodium Chloride Diffusion in Low‐Acid Foods during Thermal Processing and Storage

This study aimed at modeling sodium chloride (NaCl) diffusion in foods during thermal processing using analytical and numerical solutions and at investigating the changes in NaCl concentrations during storage after processing. Potato, radish, and salmon samples in 1% or 3% NaCl solutions were heated at 90, 105, or 121 °C for 5 to 240 min to simulate pasteurization and sterilization. Selected samples were stored at 4 or 22 °C for up to 28 d. Radish had the largest equilibrium NaCl concentrations and equilibrium distribution coefficients, but smallest effective diffusion coefficients, indicating that a greater amount of NaCl diffused into the radish at a slower rate. Effective diffusion coefficients determined using the analytical solution ranged from 0.2 × 10^–8 to 2.6 × 10^?8 m²/s. Numerical and analytical solutions showed good agreement with experimental data, with average coefficients of determination for samples in 1% NaCl at 121 °C of 0.98 and 0.95, respectively. During storage, food samples equilibrated to a similar NaCl concentration regardless of the thermal processing severity. The results suggest that sensory evaluation of multiphase (solid and liquid) products should occur at least 14 d after processing to allow enough time for the salt to equilibrate within the product.     

Predicting Cantaloupe Bruising Using Non-Linear Finite Element Method

In this study, the mechanical properties of the skin and flesh of cantaloupe were determined by individual experiments and then finite element simulation was developed for cantaloupe fruit under compression loading. The applied deformations were equal to 10, 20 and 30% of rupture deformation or 4.5, 9 and 13.5 mm, respectively. The results showed that the internal tissue of fruit reached to yield point in 20% of whole deformation or in force 90 N and the internal failure occurred with no visibility. The statistical comparison of finite element method results with experimental data was performed. The results showed finite element method was able to determine the force threshold of internal bruising for cantaloupe.     

食品工业中的新型杀菌技术

本文对食品工业中的新型杀菌技术,如高压脉冲电场、超声波、通电杀菌、高压杀菌、远红外线杀菌、脉冲强光杀菌等的机理、优点及应用进行了综合分析介绍,指出这些新型杀菌技术开发利用前景广阔,应进行深层次的研究,以促进食品工业的发展。