干燥机的最新发展(二)

本文论述了以过热水蒸汽作为干燥介质代替热风的干燥新技术的原理、优越性、存在的问题以及发展前景，并对微波对流干燥器的原理、特点等作了描述。     

Low-Temperature Drying Using a Versatile Heat Pump Dehumidifier

A drying system incorporating a commercial 2.3 kW heat pump dehumidifier was designed and constructed. The HPD was equipped with an external water-cooled condenser that rejected excess heat out of the system. The design of the system allowed for conducting drying with recirculation of air as well as use of electrical heaters. In an open mode, the drying could be carried out simultaneously with room dehumidification and water heating in the secondary condenser. Drying experiments were conducted with apple and comparisons were made between HPD assisted drying (partial and complete) and hot air drying (at 45 and 65°C). The HPD dried fruit exhibited better rehydration properties than the hot air dried samples. Water activity of the HPD dried samples was noticeably lower than that of the hot air dried samples at the same water content, indicating that the residual moisture was probably held under higher tension in the former. In terms of energy consumption, the process of HPD assisted drying is more expensive as much of the energy input is rejected at the secondary condenser as excess heat.     

现场总线在烘丝控制系统中的应用

系统采用现场总线完成过程控制,即可保证现场就地实时控制,又可以完成整线连锁控制,节约现场布线,降低成本,保证系统工艺控制精度和整线控制可靠性。     

基于LSSVM的木材干燥建模研究

针对木材干燥过程的强非线性特点,提出以最小二乘支持向量机LSSVM建立木材干燥基准模型.通过实验用小型木材干燥窑实际干燥过程中采集的数据作为训练样本进行仿真实验,结果表明基于LSSVM的木材干燥模型预测输出能够准确反映干燥过程木材含水率的变化,模型结构简单、预测精度高、泛化能力强,验证了LSSVM对木材干燥过程建模是一种可行而有效的方法.     

基于卡尔曼滤波的木材含水率在线估计

为解决木材干燥过程木材含水率检测精度低的问题,提高木材干燥的自动控制水平,针对以含水率为基准的干燥过程,提出了应用卡尔曼滤波进行木材含水率在线估计方法。为验证该方法的有效性：首先建立了基于含水率基准加入高斯噪声数据集的卡尔曼估计模型,并在此模型基础上对实验测得的数值进行了在线估计和比较,结果表明卡尔曼滤波方法具有较好的估计精度。     

组态软件在干燥实验装置上的应用

本文介绍了MCGS组态软件在干燥实验装置中的开发与应用,阐述了实验台的原理、结构与功能。实验台主要由工控组态软件、计算机、数据采集卡、相应传感器件构成的数据采集与监控系统及干燥装置组成,设计结构紧凑,使用灵活,操作界面友好,经投入使用效果良好。     

Suitable properties of ink to create inkjet-printed surface-directed microchannels that utilize the pinning effect of a triple line on a rough surface

If microfluidic devices can be directly produced using printing techniques, the combination of microfluidics and printing techniques for other applications, such as printed electronics, will make all-printed highly-functionalized microfluidic devices possible. Therefore, we have made efforts to develop a technique for producing microfluidic devices using an inkjet printer. The microchannels that could be created using this technique were a kind of surface-directed channels that utilize the pinning effect of a triple line on a rough surface. In this study, we focused on what were the required properties of the printer ink during the wetting and drying processes of the ink. As a result, one of the properties required during the wetting process was that the advancing contact angle of the ink should be smaller than a certain value, which depended on the average volume of the ink drops ejected from the printhead and the number of drops per unit area. The receding contact angle should be smaller than about one third of each advancing angle. In addition, during the drying process, a small amount of surfactant added to the ink played a critical role in order to leave a continuous stain of the ink. As an application of this inkjet-printed channel, we also created a device for mixing aqueous solutions.     

电子管烘干设备结构设计

就某型电子管烘干设备的主要技术特点、结构组成作了阐述,并针对研制过程中所遇到的若干问题进行了探讨。     

DRYING KINETICS DERIVED FROM DIFFUSION EQUATION WITH FLUX-TYPE BOUNDARY CONDITIONS

A novel approach to drying of both hygroscopic and non-hygroscopic capillary - porous materials is presented. The equations for drying kinetics are obtained, based on the analytical solution of the differential equation of diffusion with a boundary condition in the form of the flux. Theoretical drying curves generated form the model solution compare well with experimental literature data for drying of materials with different sorption properties exemplified by wool bobbins, brick slabs and corn kernels.     

Structure of Crack in Thermally Dried Sludge Cake

We examined in this work the drying characteristics of wastewater sludge, considering the weight loss using an electronic balance and the morphology change of drying cake by an X-ray micro-computerized tomography scanner (micro-CT). The drying rates for sludge cake was 50-60% of the pure water test. The corresponding micro-CT images were scanned to explore the change in cake volume and development of internal crack over drying. The Otsu's method was applied to bilevel the scanned images, based on which the three-dimensional model for crack's internal structure was reconstructed. The cake porosity and the geometric factors of cracks, such as the compactness, the boundary fractal dimension, and the Sierpinski carpet fractal dimension, were evaluated. The shrinkage of cake volume and the development of internal crack occurred simultaneously. The skin layer formed by the former mechanism retards further drying. On the other hand, the internal cracks were shown to exhibit zigzagging with a noncircular cross section and fractal-like boundary, which should be able to enhance local drying. A possible role of change in crack structure on the rate of drying was discussed.