水性油墨热风干燥机理及数学模型研究

当前,随着环保及食品、药品安全问题越来越多的被人们重视,绿色印刷与包装技术的研究和应用也越来越广泛,其中水性油墨逐渐被市场接受,但是,目前国内与水性油墨配套的印刷设备却存在烘干效率低,印刷速度难以提升的问题。为解决此问题,本论文以Logarithmic模型为基础,分析水性油墨的热风挥发干燥机理和过程。在热风温度为50℃,热风流速为6m/s的条件下,并假设实验条件遵循费克第二定律:干燥初始阶段,固体基质的流体均匀分布;干燥过程中,扩散系数保持不变;表面传热传质阻力忽略不计以及一维扩散等。在该试验条件下,对水基油墨在干燥过程中残留流体比例进行测量并记录,然后对实验数据进行非线性回归(SPSS统计软件),以相关系数的平方作为评价模型的依据,并对Logarithmic模型进行修正,得出与水性油墨于燥过程吻合的改良模型。最终模型能够准确预测水性墨干燥的效率,该模型能够为水性墨印刷设备设计提供基础数据,同时,对相关印刷设备印刷速度的提高具有积极意义。     

纸浆模塑薄层干燥实验及动力学模型分析

利用隧道式干燥器在不同热风温度、流速及物料厚度条件下,研究了干燥环境对纸浆模塑干燥过程的影响;并采用Page等六种薄层干燥模型对降速干燥过程进行拟合,分析了其有效扩散系数。结果表明:较高的热风温度、热风流速及较薄的物料厚度能够显著缩短干燥时间;Logarithmic模型可以准确预测纸浆模塑干燥曲线;热风温度、热风流速和物料厚度对有效扩散系数影响明显。     

三华李果糕热风干燥特性及数学模型的建立

利用洞道式热风干燥装置,探讨不同的热风温度对三华李果糕干燥水分比MR和干燥速率v的影响.采用非线性回归法将7种常见薄层干燥数学模型与实验数据进行拟合,并追加验证实验.结果表明:三华李果糕热风干燥是内部水分扩散控制的降速干燥过程,且干燥温度不宜高于70℃.比较各模型的决定系数R2,卡方X2和标准误差eRMSE,Logarithmic模型能较好地描述和预测三华李果糕的干燥过程,其干燥动力学方程为:MR=1.0915exp[-(0.51093-0.01497T+ 0.00016T2)·t]-0.13348.     

蔗渣热风干燥和微波干燥特性比较及评价

为了探讨蔗渣干燥特性,利用功率分别为中火档、中高火档的微波对蔗渣进行微波干燥,同时分别在90℃、100℃的条件下进行热风干燥实验对比,研究了不同干燥方法蔗渣的干燥特性,计算了不同实验条件下的有效水分扩散系数。结果表明：整个干燥过程,微波干燥相对于热风干燥时间缩短了80％以上;热风干燥、微波干燥蔗渣的平均绝干含水量分剐为7．56％、0．98％;在实验条件范围内,微波干燥过程内部水分扩散速度较热风干燥速度要大。     

冻融预处理对山楂热风干燥特性的影响

研究了不同冻融次数和温度条件下大果山楂的热风干燥特性和水分有效扩散系数。结果表明:冻融预处理对大果山楂的干燥特性有显著影响,随着冻融次数的增加,干燥时间缩短,干燥速率有所提高;冻融大果山楂在不同干燥温度下的干燥过程可采用Logarithmic模型进行描述;冻融大果山楂在不同干燥条件下的有效水分扩散系数(Deff)随着冻融次数的增加而变大。     

花椒热风干燥特性的实验分析与数学模型

分析了花椒在不同热风干燥实验条件下的实验数据及相应的干燥曲线,建立了花椒热风干燥过程中水分比与温度、风速、干燥时间之间的模型MR=1.0033exp[-(-0.4348+0.0123T+0.0076V)t],描述了在给定条件下花椒热风干燥过程中的动力学变化规律,可精确预测花椒干燥过程中水分比的变化。     

无核葡萄干燥特性的研究

为了为葡萄热风干燥及设备参数的调整提供理论依据,对无核葡萄进行热风干燥实验,研究其在不同热风温度、不同处理条件下的热风干燥特性.分析实验得出了不同务件下的干燥特性曲线,结果表明:温度对葡萄干燥的影响很大;葡萄的干燥过程是降速干燥过程.     

胡萝卜片热泵—热风联合干燥特征与模型化研究

利用热泵-热风联合干燥装置,以胡萝卜片为原料,进行了干燥实验.为了提高干燥产品品质以及缩短干燥时间,对干燥温度和空气速度等参数进行了探索,研究了干燥过程的特征,确定了前期低温热泵干燥、后期短时热风干燥的联合干燥方式,建立了干燥过程数学模型且与实验结果进行了比较.     

鲍鱼热风干燥动力学及干燥过程数学模拟

研究了鲍鱼在不同热风干燥温度下的干燥动力学特点,并构建了干燥过程的数学模型。热风干燥温度选取60、65、70、75、80℃;风速恒定为1m/s。干燥方法采取间歇干燥,分两个阶段进行。利用理论模型—扩散模型,和常见经验模型—Newton模型、Henderson and Pabis模型、Logaritmic模型、Two-terms模型、Page模型及Modified Page模型,对鲍鱼干燥过程的两个阶段分别进行描述。实验结果表明:鲍鱼热风干燥只经历降速阶段,水分扩散在鲍鱼干燥的过程中起主导作用。通过对实验数据进行统计分析,得到适合鲍鱼热风干燥的模型为Page模型(第一阶段干燥)和Two-terms模型(第二阶段干燥),模型的预测值与实际值比较吻合(Page模型r2>0.999,s<1%;Two-terms模型r2>0.997,s<2%),可以用来描述鲍鱼的热风干燥过程。     

罗非鱼片的热风干燥模型及能耗研究

对罗非鱼片进行了热风薄层干燥实验,通过实验数据建立了罗非鱼片的热风干燥的水分比与干燥时间关系的数学模型,根据建立的模型进行了拟合检验,结果显示模型的预测值与实测值拟合良好。此外,还研究了罗非鱼片热风薄层干燥过程中的能耗特点,结果表明,热风薄层干燥罗非鱼片的单位能耗降湿量最低为423.4g/kW·h,最高为1147.7g/kW·h。鱼片越小,每批干燥量越少,则单位能耗降湿量越大。     

Drying characteristics of textured soy protein

Textured soy proteins (TSPs) are commonly used as a functional ingredient in several food applications; its process involves a drying step which is one of the most relevant and challenging processes in the food industry. The drying curves of two commercial types of TSPs were determined in a pilot air‐dryer operated at three different drying air temperatures and velocities, with two different heights of product layer. The results showed that drying air temperature significantly influenced all the experimental curves. The height of the product layer influenced only the drying curves of TSP Type I. The effect of drying air velocity was found to be lower. A two‐constant exponential model and a ten‐constant mathematical model were used in the development of a unified model capable of predicting the drying curves of these types of TSP. The experimental curves were successfully predicted in the range of humidity of industrial interest.     

Drying rate control in the middle stage of microwave drying

Microwave drying of apples at constant temperatures follows typical drying curves. The middle stage of the drying process shows a faster drying rate and accelerated moisture evaporation. Meanwhile, more flavors are lost, surface color is degraded, and charring often occurs in this stage. To improve the drying effects, drying curves were controlled and changed in this study. The drying curve was linearized by automatically varying drying temperatures in the middle stages. The controlled drying process therefore led to an optimized temperature profile. To simplify the drying methods, apples were further dried with the obtained temperature profile, while drying curves were online monitored but not controlled. It was proved that slowing down the drying rate in the middle stage could improve the product quality in terms of color, flavor, and overall appearance, while the drying time and energy consumption were still acceptable (within 200 min and 22 kJ/g, respectively).     

纳米二氧化硅改性水性丙烯酸树脂的合成及性质研究(英文)

近年来,环保型水性树脂在印刷及涂料领域受到了越来越多的关注。与溶剂型油墨相比,由于水性油墨具有较高的表面张力,较低的干燥速度,容易发泡,pH稳定性及不同的黏度特性,使水性油墨的研制非常困难。但随着化学和印刷工业的发展,水性油墨将逐步取代溶剂型油墨。本文以内烯酸、甲基丙烯酸甲酯、丙烯酸丁酯、甲基丙烯酸-2-羟乙酯等水性树脂为原料,正丁醇为溶剂,过氧化二苯甲酰为引发剂,二甲基乙醇胺为pH调节剂,通过溶液聚合的方式得到丙烯酸树脂。合成的丙烯酸乳液与纳米二氧化硅通过乳液聚合的方式得到纳米二氧化硅改性水性丙烯酸乳液,并且利用此乳液制备水性油墨。通过动态光散射仪与电子显微镜来研究粒子的分布及表面形貌,并且还研究了油墨在玻璃板上的附着力及油墨的流变性能。     

棉织物干燥过程热湿传递特性软件计算与分析

以单层多孔薄棉织物为对象,分析并建立其热风干燥过程中的热质传递机理及数学模型,得到织物在烘干过程中含水率与温度的变化规律,并采用MATLAB APP designer设计了棉织物传热传质数值计算软件,简易又直观地显示了各干燥段干燥时间与温湿度变化曲线。结果表明,薄棉织物在干燥过程中,内部温度与含水率的梯度基本可忽略不计,薄棉织物恒速段干燥时间占总时间的70%以上,但在结束恒速干燥段后内部仍有一定的吸附水含量。可为印染热定形机的风道结构设计和棉织物热定形工艺参数的设定提供理论参考价值。     

凹版印刷机干燥系统的研究

随着包装印刷工业的快速发展,凹版印刷技术在国内的发展极其迅速,凹印机烘干速度越来越成为制约印刷速度提高的关键因素之一。通过对干燥机理,干燥方式．以及凹印机干燥装置系统的深入分析。提出了对凹印机干燥系统进行全面改进的几项重要措施。如改进空气喷嘴系统、烘干装置的控制系统、凹印机的烘道曲线等。这对凹印机的改进设计和印刷速度的提高起到重要的作用。     

Study of the drying behaviour in peeled and unpeeled whole figs

Aim of this study was to estimate the effect of peeling on drying kinetics and effective diffusivity D_eff of figs (Ficus carica L. var. tsapela) during air-drying. For this purpose three temperatures (45, 55 and 65 °C) were tested. The Logarithmic model was chosen to describe the drying curves among seven drying models. The estimated drying constants were associated with the drying temperature by an Arrhenius type equation. The ratio of peeled to unpeeled relaxation times was found to be 0.54 ± 0.16. The D_eff of figs (peeled and unpeeled) was estimated by the method of slopes. The D_eff of the peeled figs was higher than this of the unpeeled figs presenting smaller differences as drying temperature was increased. This behaviour was attributed to the case hardening effect which is faster developed as the drying rate increases during high temperature drying.     

玉米籽粒缓苏干燥过程动力学分析

对玉米籽粒的缓苏干燥过程进行了理论分析,并假设玉米籽粒为轴对称结构、各向同性的均匀物质,建立了玉米籽粒的缓苏干燥数学模型,利用COMSOL Multiphysics模块进行了热质传递过程的模拟研究。结果表明,该模型可较好地模拟玉米籽粒的干燥过程。利用该模型模拟研究了不同干燥条件下玉米籽粒温度、干燥时间、缓苏时间、缓苏度的变化及其对干燥速度的影响。结果表明,玉米籽粒内外温度在3~5 min内即可达到热风温度,玉米籽粒内部最大水分梯度出现在热风干燥5~10 min后,不同干燥阶段不同初始含水率对缓苏度的影响很小,缓苏60 min水分梯度可以基本消除。利用该优化工艺参数对玉米籽粒交替进行热风干燥和缓苏干燥,可使总的热风干燥时间最少,实现节能目的。     

Proposal of a new reference method to determine the water content of dried dairy products

The water content of milk powders is “officially” determined by drying. The result of drying techniques is, however, the mass loss the sample undergoes under the conditions applied. No differentiation between water and other volatile substances is made. A particular problem is the lactose that is present in all dried dairy products. The α-form contains one mole of water of crystallisation per mole. This water fraction is not determined completely by ordinary drying methods. How much of the crystallised water is detected depends very much on the conditions applied. The entity determined by drying is not defined. It is only a tradition to regard the mass loss thus detected as water content. More and more, however, the expression moisture content is used for the result of drying techniques, although this term is also unsatisfactory and misleading. The discrepancy between mass loss on drying and water content becomes more pronounced when the product has high crystalline lactose content, such as whey powders or lactose itself. In these cases the difference between mass loss and water content can be quite significant. The existing reference method for moisture determination in dried milk is therefore not reasonably applicable on dairy products with high crystalline lactose content. It could be shown that the water content of dried dairy products can be determined using the Karl Fischer titration independently of the level of crystallisation water. The results are not only more accurate but also more precise than those obtained by the reference drying method. It is therefore proposed to introduce the Karl Fischer titration as reference method for dried dairy products.     

粮食干燥工艺与设备中存在的问题及对策

对粮食干燥工艺及设备进行了分析，认为其问题为：中小型干燥设备缺短、干燥工艺不合理、干燥质量差、能耗较高。对此，应采取的对策为：发展中小型干燥设备、探索干燥新工艺、采用干燥新能源。     

Effects of drying conditions in hybrid dryer on the GABA rice properties

In this study, pre-germinated rough rice was dried under various conditions using a hybrid dryer that incorporated heat pump dryer with fluidized bed drying (FBD) system in order to compare with the single-stage drying by hot air dryer. The main objective was to investigate the effect of drying conditions on the cooking and physical properties, nutrients and sensorial qualities of GABA rice products. It appeared that the FBD at 100–140 °C led to noticeable increase of head rice yield. The germination process caused the decline of gelatinization enthalpy of brown rice flour, the change of pasting properties, the reduction of cooking time and escalation of the total phenolic content, antioxidant activity and GABA content. The FBD at higher temperature significantly raised the degree of starch gelatinization and caused longer cooking time, higher hardness and adhesiveness of cooked GABA rice. Three-stage drying comprising FBD at 60 °C for 10 min in the first stage followed by FBD at 100 °C in the second stage and then heat pump drying at 45 °C together with tempering step between drying stages was recommended due to its superior GABA rice product quality.