Investigation of the Effects of Microwave Treatment on the Optical Properties of Apple Slices During Drying

The objective of this work was to study the changes of optical properties of apple (Golden Delicious) slices during drying. The optical parameters compared on the basis of Hunter values (L, a, b) changes as well as total color difference (Δ E) and browning index (BI). The effect of coating materials including carboxymethylcellulose (CMC), starch, and pectin as well as microwave treatment on optical properties and microstructure of dried samples were investigated. To analyze the effects of these processes on microstructure, scanning electron microscopy (SEM) was employed. Results showed that optical properties as well as microstructure of apple were affected by coating material and drying condition. Coated samples by CMC had a lower L and higher BI, but different results in the presence of starch were obtained. Microwave treatment in the presence of appropriate coating materials could improve the optical properties of dried apple slices.     

Multi-Zone Drying Schemes for Lowering the Residual Solvent Content during Multi-Component Drying of Semicrystalline Polymers

The development of a glassy skin in multicomponent semicrystalline polymer systems limits the diffusion of solvents out of the system and increases residual solvent levels. Based on the results of a mathematical model that we had previously developed, we have proposed a multi-zone drying scheme aimed at lowering the residual solvent levels by taking into account the effect of interactions between the various solvents as predicted by the model. This article focuses on the application of this model to develop optimal drying schemes and to verify the effectiveness of these predictions using experimental techniques. The mathematical model developed previously to study the diffusion of multiple solvents and changes in the crystallinity of semicrystalline polymer systems during drying incorporates many features including Vrentas-Duda diffusion theory, solvent-induced crystallization kinetics, as well as glass transition effects and skinning of the film. The multi-zone drying system was developed by varying the drying temperature in each zone as well as changing the partial pressure of individual solvents during the drying process. The effectiveness of the multi-zone drying schemes predicted by the model was validated experimentally using thermogravimetric methods. The polymer-solvent system chosen was a poly(vinyl alcohol)-water-methanol system. Our experimental data suggested that the multi-zone drying schemes were superior to a single-zone drying system through direct comparison. Further examination of the mathematical model yielded individual solvent profiles and these data reaffirmed our conclusions that a multi-zone drying scheme has the ability to reduce the effect of solvent trapping and thus lower the overall residual solvent content.     

Drying and property studies on protective coatings formed by spontaneous surface polymerization

Drying studies on a protective coating formed by spontaneous polymerization on aluminum are described. The polymer coating studied here was formed from styrene, n-phenyl maleimide (NPMI), bismaleimide (BMI), and 2-(methacryloyloxy) ethyl acetoacetate (MEA). The coating successfully changed into an adherent film through drying in the presence of a coalescing solvent. Drying at a high temperature (> 170°C) enhanced the performance of the coating in terms of corrosion resistance and adhesion. It was found that the drying process involved removal of surface water on the substrate followed by formation of a dense protective layer associated with thermal crosslinking of g -diketone functional groups in the coating. The reaction mechanism, glass transition temperature, adhesion strength to aluminum, and corrosion resistance of these coatings are reported. The resultant coatings show excellent adhesion strength in a torsional test and very good resistance under the ASTM B-117 accelerated salt fog test.     

Drying characteristics of sweet cherry

The effects of alkali emulsion of ethyl oleate and air temperature (60, 70 and 75 °C) on the drying characteristics of sweet cherry were studied using a hot air dryer at a constant air velocity of 2.0 m/s. It was observed that both the alkali emulsion of ethyl oleate and air temperature affected the drying time. The drying times of pre-treated samples were 19.5-22.6% shorter than those of control samples. Five semi-theoretical thin-layer models, namely, Lewis, Henderson and Pabis, Logarithmic, Page, Wang and Singh models were used for the modeling of the drying kinetics. The fit quality obtained with each model was evaluated using statistical tests. After comparing experimentally obtained values with the calculated values from the models, it was concluded that Page model represents the drying characteristics better than the other models. The effective moisture diffusivity was determined by using Fick's second law and was observed to lie between 5.683 × 10⁻¹⁰ and 1.544 × 10⁻⁹ m²/s for the pre-treated and control samples. Rehydration ratio was significantly affected by pre-treatment and air temperature. It was found to increase proportionally with the increase in air drying temperature.     

Variation in Drying Behavior and Final Moisture Content of Wood during Conventional Low Temperature Drying and Vacuum Drying of Betula pendula Timber

Conventional and vacuum drying experiments were conducted on Betula pendula timber, which was sawn from trees felled during three different seasons. The influence of the wood procurement season on drying behavior differed, on the one hand, between the drying phases above and below 30% moisture content in the conventional drying, and, on the other hand, between the conventional and vacuum drying methods. During the first steps of the conventional drying process, relative humidity in the kiln, as well as drying time and drying rate, varied according to the felling season. Variations in environmental conditions outside the kiln and the seasonal variation in the physical properties of the wood were presumed to be the reasons for differences in drying behavior. The difference in moisture content gradient, i.e., the difference in final moisture content between the inner wood and the surface layer of boards, was greater in conventionally dried timber than in vacuum-dried timber. In conventionally dried timber there was a clear seasonal variation in the gradient of final moisture content, which was greatest for winter-felled wood. The premature drying of the surface layer during the first steps of the conventional drying process of winter-felled wood was the reason for the higher gradient of moisture content. Storage of wood as logs decreased the standard deviation of the final moisture content.     

新型光稳定剂产品应用于水性光固化涂料的研究

水性光固化涂料已解决了使用传统紫外光固化涂料所释放VOC的问题,而环保型涂料所遭遇的挑战之一,是需要光稳定剂来保护涂料预防光劣化产生。针对水性光固化涂料开发了一种新型复配型光稳定剂EVERSORB AQ7,试验结果显示:针对3种不同类型光稳定剂添加至2种不同类型溶液-水和水性光固化树脂中进行分散过滤试验,EVERSORB AQ7分散效果最好,并且不会对光固化速度产生负效冲击,另外根据实验室人工加速老化试验结果显示,增加EVERSORB AQ7在水性光固化涂料中的有效浓度,可以增强相对的保护效果,增加涂料的膜厚可以得到某种程度的保护效果。     

牡丹花干燥过程中色变机理分析

在牡丹花红色素理化性质研究的基础上，对品种为“洛阳红”的牡丹花在干燥过程和干花自然存放过程色变的机理作了探讨。研究发现，牡丹花干燥过程中细胞内水分去除引起的pH值变化和细胞内酶的作用是导致牡丹花干燥过程花瓣变色的两个决定性因素。在牡丹干花自然存放过程中引起花材色变的主要因素是紫外线和氧气。     

Advanced Exergy Analysis of a Heat Pump Drying System Used in Food Drying

Exergy analysis has been used as a powerful tool to study and optimize various types of energy systems. However, the methodology of splitting the exergy destructions (the so-called advanced exergy analysis) allows for a further understanding of the exergy destruction values to improve the system efficiency. In this study, advanced exergy analysis was applied to a pilot-scale heat pump drying system used in food drying for the first time to evaluate its performance at different drying temperatures. The results showed that inefficiencies within the compressor and condenser were mainly due to the internal operating conditions and the efficiencies in the evaporator and heat recovery system could be improved by structural improvements of the whole system and remaining system components.     

超支化聚合物的溶液相行为与涂料应用

通过新的合成方法相继制备超支化聚酯、聚醚、聚酯酰胺及聚丙烯酸酯等,其结构越来越复杂,应用也越来越广泛.本文概述了超支化聚合物椭球型的结构特征和无序支化到可控的制备方法的发展.重点介绍了其溶液无链缠绕的流变特性和相行为研究进展,通过末端官能团的改性可改变超支化聚合物的溶解性、流变性和功能化.对其在涂料领域的应用如固化剂、...     

氮掺杂纳米TiO_2改性涂料及其抗菌性能

将自制的氮掺杂锐钛矿型纳米二氧化钛光催化剂作为功能性组分,加入耐光催化氧化的硅丙乳胶涂料中,制备出一种新型光催化功能性建筑涂料,实现了可见光光催化效应。使用紫外-可见光吸收光谱研究该功能性涂料对紫外线的吸收能力;采用菌落计数法研究该涂料在可见光照射下对金黄色葡萄球菌的杀灭性能。同时分析了纳米粉体种类、引入量及方式对涂料紫外线的吸收性能和抗菌性能的影响。     

Drying of Diced Carrot in a Combined Microwave-Fluidized Bed Dryer

Drying of diced carrot (∼90% wet basis) was carried out in a laboratory microwave fluidized-bed dryer (MFB) and in a standard fluidized-bed dryer (FB). It was found that the drying time in the MFB dryer is 2-5 times shorter than in the FB dryer. Drying efficiency (DE) is a function of moisture content, microwave power and temperature of drying agent. Higher values of DE are obtained for MFB dryer. For both drying systems the water removal was proceeding in two-stage falling rate period (except short initial term).     

Drying characteristics of millet in a continuous multistage fluidized bed

The effects of gas velocity, inlet gas temperature and the solid feed rate on the drying efficiency, the outlet solid moisture content, bed temperature in each stage, the outlet gas humidity and temperature in a rectangular acryl multistage fluidized bed (0.172 m×0.192 m×1.5 m-high) with a downcomer (0.04 m-I.D.) were investigated. The experiments were performed by using 1.9 mm millet particles. The final moisture contents of the solids increased with increasing the solid feed rate. The drying efficiency increased with increasing the wetted solid feed rate but decreased with increasing the inlet gas temperature. The drying performance of the multistage fluidized bed was compared with the single-stage fluidized bed and found to be superior under identical operation conditions. The model predicted values were well matched with the experimental data in the multistage fluidized bed dryer. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

枸杞干燥专利技术分析

采集了1985年—2013年3月中国枸杞干燥专利文献,对我国枸杞干燥装置、干燥工艺和枸杞制干护色剂等相关技术专利进行了分析研究。数据显示:近30年来,枸杞干燥方面获得授权的专利只有22项,总体数量很少,反映出我国枸杞干燥技术进步相对较慢。     

Effect of a Drying Pretreatment on Morphology of Porous Poly(Ether-Imide) Membrane Prepared Using Vapor-Induced Phase Separation

Symmetric porous membranes were prepared from concentrated poly(ether-imide) (PEI) solutions using vapor-induced phase separation (VIPS) coupled with a drying pretreatment. Moderately concentrated solutions of PEI in N-methylpyrrolidinone (NMP) (14–16 wt%) were first cast on glass plates and the solvent was then allowed to evaporate under a dry air flow up to the desired concentration (16–38 wt%) before forming the membrane structure by VIPS. The polymer concentration profiles (confocal Raman microscopy) and model predictions were in good agreement to show that the evaporation stage did not induce a polymer gradient concentration with PEI/NMP systems. These results were confirmed by examination of the final membrane morphology (SEM).     

Analysis of the Vacuum Drying Rate for Red Oak in a Hot Water Vacuum Drying System

Red oak boards of 76.2 cm (long) × 7.62 cm (wide) × 2.54 cm (thick) were dried from green moisture content (MC) to 7% MC in the hot water vacuum-drying system. These boards were dried at the pressure of 12 mm Hg and the temperatures ranging from 30 to 50°C within 25 to 70 h. Drying rates were measured and drying curves were calculated. The results showed that the drying rate was higher at higher temperatures. The vacuum drying was faster when wood MC was above 30% than when it was less than 30%. The individual samples did not dry at the same drying rates even at the same drying conditions because of anatomical variations between boards.     

Effect of a Drying Pretreatment on Morphology of Porous Poly(Ether-Imide) Membrane Prepared Using Vapor-Induced Phase Separation

Symmetric porous membranes were prepared from concentrated poly(ether-imide) (PEI) solutions using vapor-induced phase separation (VIPS) coupled with a drying pretreatment. Moderately concentrated solutions of PEI in N-methylpyrrolidinone (NMP) (14-16 wt%) were first cast on glass plates and the solvent was then allowed to evaporate under a dry air flow up to the desired concentration (16-38 wt%) before forming the membrane structure by VIPS. The polymer concentration profiles (confocal Raman microscopy) and model predictions were in good agreement to show that the evaporation stage did not induce a polymer gradient concentration with PEI/NMP systems. These results were confirmed by examination of the final membrane morphology (SEM).     

Influence of Factors on the Drying of Cassava in a Solar Simulator

ABSTRACT

In tropical countries, sun drying is still the most popular method used for processing root and tuber crops like cassava and yam. Relatively very little has been done on studying the kinetics of sun drying a bed of chips of cassava and similar crops, but this information is invaluable in finding options for reducing drying time and costs, and increasing tonnage produced. This project studied some factors that have an effect on the sun drying rate of cassava chips. The factors were ambient temperature, relative humidity, radiation intensity, air velocity, and loading density.

A solar simulation chamber was constructed so that drying could be achieved under controllable conditions similar to those obtained in sun drying. Experiments carried out in the simulator revealed that temperature had the most significant effect on drying rate, followed by air velocity, and radiation intensity. Regression equations were developed relating the drying rate with the factors studied.     

Drying Characteristics of Porous Materials in a Fluidized Bed under Reduced Pressure

Abstract

The drying of porous materials immersed in the fluidized bed under reduced pressure was performed, and the results were compared with those of hot air drying. The pressure in drying chamber was changed (5.0–101.3 kPa) and the effect of it was examined.

The temperature of the sample center becomes lower as the pressure in drying chamber decreases, and the temperature in fluidized-bed drying is higher than that in hot air drying at the same pressure. The effect of pressure in drying chamber on the sample temperature is significant for different temperatures of drying gas.     

Measurements of Concentration Profiles in Polymeric Solvent Coatings by Means of an Inverse Confocal Micro Raman Spectrometer—Initial Results

Concerning quality and drying time of a process the key issue is the progression of the concentration profiles within the film during drying. This contribution reports on the development of a new measuring technique, an Inverse-Confocal-Micro-Raman-Spectrometer, for online measurements of concentration profiles during drying in thin (5-200 µm) polymeric solvent coatings. The spatial and temporal resolution of the measurements is up to one micron and one second. A calibration method has been developed by taking Raman spectra of different, precisely concentrated samples in sealed quartz glass cells and by calculating the ratio of the intensities of the characteristic Raman peaks. The accuracy of this basic calibration method is very good over a wide concentration range. Initial investigations were carried out on the polymer solvent systems: polyvinyl acetate(PVAc)-toluene, PVAc-methanol, PVAc-benzene, and PVAc-methanol-toluene, PVAc-methanol-benzene.     

溶剂气浮法分离有机物稀溶液的研究进展

论述了溶剂气浮法在分离有机物稀溶液方面的研究现状,对其所涉及的工艺和工程等关键问题作了介绍,对近期在工业应用中的中试研究进行了论述。展望了利用溶剂气浮法分离有机物稀溶液的工业化应用前景和研究重点。