粘胶短纤维的热风干燥特性研究

利用自行研制的热风干燥实验装置研究了热风温度、纤维层厚度、热风速度、纤维层含水率等对粘胶短纤维干燥特性的影响规律。结果表明:粘胶短纤维的热风干燥过程可依次分为4个阶段,即蒸发预热段、表面自由水分干燥段、纤维内部自由水分干燥段和纤维内部结合水分干燥段;热风温度对纤维第2阶段干燥速率的影响很大,100~140℃的含水率相差37.3%,对后面阶段的干燥速率影响较小,最佳热风温度为120℃;纤维层厚度对粘胶短纤维的第3阶段干燥速率略有影响,纤维层厚度以12 cm为宜;热风速度对短纤维干燥速率的影响很大,热风速度以2.0 m/s为宜,纤维层含水率对第2和第3阶段的干燥速率影响较大,应尽量减少纤维层的表面含水率。     

含水粒子层的热风对流干燥特性

用数值和实验两种方法研究了含水玻璃球粒子层的热风对流干燥特性,建立了基于一维假设下的热量和质量传递的动态数学模型,并用有限差分法进行数值求解,得到含水率,温度与时间的关系曲线和干燥行性曲线,计算结果与实验结果吻合较好,结果表明,干燥速度与粒子直径没有明显的关系,干燥曲线的形状与粒子层厚度无关。     

含水粒子层的红外线干燥

用数值和实验两种方法研究了玻璃球粒子层的红外线干燥特性．首先建立了基于一维假设下的热量和质量传递的动态数学模型,并用有限差分法进行数值求解.得到含水率、温度与时间的关系曲线和干燥特性曲还建立了一套实验装置,测量了干燥过程中含水率和层内温度随时间的变化曲线．计算结果与实验结果吻合很好．结果表明,层内温度分布和干燥速度受辐射线波长、入射热量、粒子直径、粒子层厚度的影响．远红外线比近红外线具有更高的能量效率和干燥速度．     

杉木木束热风循环干燥参数对干燥效率与能耗的影响

利用热风循环干燥的方法，对铺装方式、转筒速度、装载量、初含水率、气流温度、气流速度等影响木束干燥效率和能耗的因素进行实验研究，探讨木束热风循环干燥参数对干燥时间和能量消耗的影响。实验结果表明，各参数对干燥结果的影响程度不一，按显著程度排序为：气流速度、初含水率、气流温度、装载量、铺装方式、转筒转速。     

竹条干燥特性的实验研究

对竹条的热风对流干燥特性进行了系统的实验研究。讨论了干燥方式， 热风速度和温度等因素对干燥过程的影响； 从干燥过程的基本原理出发， 导出了干燥过程的数学模型； 利用此模型对实验结果进行回归整理， 得到了反映竹条干燥特性的实验关系式。     

盐泥颗粒热风干燥特性及动力学模型

为优化盐泥颗粒干燥设备及结构参数，搭建热风干燥实验装置对盐泥颗粒进行热风干燥实验，研究不同风温、风速和堆积厚度对盐泥颗粒热风干燥特性的影响。对不同条件下的干燥特性曲线，通过比较决定系数R²、卡方x²和标准误差ESME等指标，评价5种常用干燥动力学模型对干燥曲线的拟合结果。结果表明：Midilli模型可以预测盐泥颗粒热风干燥过程水分的变化规律，模型预测的干燥曲线与实验干燥曲线有较高的拟合度。盐泥颗粒热风干燥过程中干燥速率逐渐下降，热风干燥特性与风温和堆积厚度密切相关。当温度从50℃增加到80℃时，有效水分扩散系数由2.038 39×10^-9 m²·s^-1增加到8.137 643×10^-9 m²·s^-1。     

基于Fick扩散模型的陶瓷坯体干燥数值模拟

本文使用Fick扩散模型对陶瓷坯体的干燥过程进行了模拟，在实际干燥工艺参数数值范围内，分析了热风速度、温度和相对湿度三个因素对陶瓷坯体内部温度、含水率和干燥速率的影响。结果表明，增加热风速度能够加大坯体表面区域的水分散失速率，但对坯体内部含水率变化影响较小；提高温度能够显著增加坯体内部的干燥速率，当温度从35℃增加至75℃时，最大干燥速率的变化幅度为46.34%;相对湿度对坯体平衡含水率影响较大，当相对湿度从5%增大至85%时，平衡含水率从0.8%增大至5.1%(均为质量分数),提高相对湿度能够改善坯体干燥均匀性，保证坯体干燥质量。模拟和试验数据基本吻合，计算结果将为进一步深入研究陶瓷坯体干燥的传热传质过程，以及后续干燥曲线的优化提供理论依据。     

明胶热风干燥特性的实验研究

采用静态法研究了明胶的平衡含湿质量分数,得到了20℃下吸湿和解吸等温线,结果表明,当空气相对湿度在16%—39%,存在吸湿滞后现象。在对流干燥实验台上进行了明胶干燥特性的实验,以不同厚度的明胶块为实验对象研究了热风温度、风速、湿度对干燥过程的影响。实验结果表明:明胶的干燥过程只有降速阶段,提高热风温度、加大风速均可以在前期提高干燥速率,但在干燥后期干燥速率反而降低;明胶块中心温度受胶块厚度、热风温度影响较大,而在实验范围内空气相对湿度的变化对明胶中心温度影响甚微;明胶的相对含湿质量分数随时间呈指数规律下降,提高风温、加大风速后明胶含湿质量分数在开始阶段下降较快,但最终含湿质量分数反而偏高。     

钛白粉浆液干燥特性实验研究

使用远红外干燥的方法研究钛白粉浆液干燥的特性及温度、料层厚度对干燥速度的影响。实验表明,选择适宜的温度和厚度对于钛白粉干燥意义重大。     

茭白片热风对流干燥模型与传质性能

为了探讨茭白干燥的传递特性,在对流热风干燥实验装置中进行了茭白片薄层干燥实验,研究了干燥温度、片的厚度对干燥过程的影响,将试验的水分比与数学模型进行了拟合,计算了不同温度下的水分扩散系数,并关联了其与干燥温度的关系.结果表明:干燥温度对干燥过程影响显著,薄片有利于水分扩散:用Page模型来描述茭白片热风干燥动力学令人满意;茭白片厚度为0.003m时,随风温升高,水分扩散系数从3.440×10-9 m2·s-1增大到6.357×10-9m2·s-1,并符合阿累尼乌斯方程,活化能为27.86 kj·mol-1.相同温度下,物料中水分的扩散系数基本不受厚度影响.     

干燥技术的进展和应用

文章侧重与化学工业关系较密切的方面，以各种干燥机的开发、改进和应用为主要线索，简要评述干燥技术２０多年来的进展与应用、技术发展趋势和存在的问题、以及我国的基本情况。     

COMPARISON OF TIMBER DRYING USING SOLAR ENERGY,ELECTRICAL HEATING AND DEHUMIDIFIER.

ABSTRACT

The performance of three different types of dryers for the hot air drying of sawn-limber planks are compared. These were the electric resistance dryer, solar dryer, and the dehumidifier dryer. Whilst the electric and solar dryers depended only upon hot air for drying, the dehumidifier dryer relied on hot dehumidified air. The results of investigations carried out on timber drying employing these three types of dryers in the Engineering Faculty are compiled and compared here in this paper. The results showed that the electric dryer produced the fastest drying lime and lowest moisture content, followed by dehumidifier drying. The solar dryer achieved a lower moisture content and a faster drying rate compared to natural drying, although the difference in drying times was marginal.     

应用涂装设备改善水性木器涂料的干燥瓶颈

从不同条件及各种涂装现场的角度来探讨水性木器涂料与不同涂装干燥设备的搭配的效果,寻找出适合水性木器涂装的设备,改善水性木器干燥瓶颈,促使水性木器涂料能广被采用。     

薄层干燥技术的研究进展

简要介绍了各种类型的薄层干燥方程,并对薄层干燥技术在农产品、水产品、中药材及其他产品干燥特性研究中的应用进行综合评述。     

干燥动力学研究综述

对现有的几种干燥速率定义及其数学表达式进行了分析和比较。简述了多孔介质的干燥动力学特性及其湿分迁移机理。对薄层干燥的半理论模型、半经验模型和经验模型作了评述。     

Through Drying of Paper

Through drying of paper of basis weight 25 to 50 g/m² was studied through 89 experiments with 22 to 90°C air at mass flow rates from 0.125 to 1.45 kg/m²s. The complete drying rate curves are represented with five quantitative parameters:moisture contents at the end of the increasing and constant rate periods, the constant drying rate, and exponents for the increasing and falling rate period relations. The constant drying rate period disappears at higher drying intensities leaving the increasing rate period accounting for as much as 37% of the drying. The constant drying rate may be controlled by thermodynamics or by transport phenomena. The critical moisture content depends on effects from the intrinsic local nonuniformity of through drying as well as on sheet average conditions. A universal set of relations was obtained for representation of the complete drying rate curve and was verified for prediction of drying rate and drying time. Through drying rates cannot be increased significantly by providing the drying air as an impingement flow.     

DRYING RATES AND DRYER CAPACITIES OF DIFFERENT SEED GRAINS

ABSTRACT

The three most commonly occurring grains --maize, rice and wheat --are compared for single kernel and deep bed drying rates. The grains are dried in a concurrent-flow (CCF) dryer; high grain temperatures are avoided to prevent deterioration of seed viability.

Wheat dries the fastest of the three grains as an individual kernel as well as in the CCF grain dryer, maize the slowest; the throughput with wheat is 23% larger than with maize, and 15% larger than with rice.     

Global R&D Needs in Drying

This paper summarizes some recent advances and general trends in drying technologies of industrial interest. The process of innovation is applied to drying R&D. The conventional drying techniques are compared with the innovative technologies. Numerous emerging technologies are listed and some examples are discussed in detail. Potential application areas for the new technologies are identified.     

Global R&D Needs in Drying

This paper summarizes some recent advances and general trends in drying technologies of industrial interest. The process of innovation is applied to drying R&D. The conventional drying techniques are compared with the innovative technologies. Numerous emerging technologies are listed and some examples are discussed in detail. Potential application areas for the new technologies are identified.