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The general objective of this work is to analyze energy input in a vacuum process with the incorporation of microwave heating. Thus, necessary criteria for designing an efficient freeze-drying operation are considered through the analysis of strategies based on the combination of different intensities of raxiiant and microwave heating.The other aim of this research topic is to study the kinetics of drying in relation to mass transfer parameters.Five freeze-drying strategies using both heating systems were used. Consequently, energy input could be related to diffusivity coefficients, temperature and pressure profiles during dehydration of the product and analyzed in comparison to a conventional freeze-drying process. 相似文献
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胡萝卜微波真空干燥试验研究 总被引:3,自引:0,他引:3
以胡萝卜为原料,采用均匀设计对微波真空干燥的微波功率、干燥温度及料层厚度进行试验研究,分析各试验条件下的水分含量及胡萝卜素含量,得到了干燥曲线和胡萝卜素保有量曲线,得出了胡萝卜失水量、胡萝卜素含量与各因素之间的回归方程,可用于描述胡萝卜的微波真空干燥特性。 相似文献
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湿法炼锌产出的中和沉铁渣作为重要的二次资源,含有大量的铁、锰、锌等有价金属,具有较高的综合回收利用价值。回收有价金属前需对中和铁渣进行脱水预处理,基于回转窑干燥法存在干燥时间长、干燥效率低、二次污染等问题,本文开展了微波干燥湿法炼锌中和铁渣实验研究,考察了微波功率、物料量对中和铁渣温升行为的影响,表明微波干燥湿法炼锌中和铁渣是可行的;实验考察了微波功率、物料量和干燥时间对中和铁渣脱水率的影响。研究结果表明:在一定程度上,中和铁渣脱水率与干燥时间和微波功率成正比,与物料量成反比。实验控制微波功率为1000W、物料量为50g、微波干燥时间为9min时,中和铁渣脱水率达98.55 %;X射线衍射、红外光谱分析展示微波干燥中和铁渣自由水脱除较为完全,但仍含有部分的结晶水;扫描电镜分析显示微波干燥较常规干燥更为均匀;与常规干燥工艺相比,微波干燥具有干燥时间短、水脱除率高、干燥均匀、清洁无污染等优势。 相似文献
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基于加热均匀性的微波干燥研究进展 总被引:1,自引:0,他引:1
微波干燥通过电磁场辐射物体而在其内部产生热量,促进物体内部水分向外部迁移,是一种先进的干燥技术。但是,微波干燥存在加热不均匀的问题。本文针对该问题,分析了导致微波加热/干燥不均匀的影响因素,综述了通过提高微波干燥室内电磁场分布均匀性及改变被处理物料位置,以改进微波加热均匀性的可行措施,最后指出进一步实现微波均匀干燥的研究发展趋势。 相似文献
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微波干燥卫生瓷的研究 总被引:1,自引:0,他引:1
本文对微波干燥和常规干燥卫生瓷的干燥过程进行了比较,对其干燥过程的不同阶段进行了讨论,并分析了台式洗面具不同部位对干燥速度的影响,证明了微波干燥卫生瓷坯体优于常规干燥的特性。 相似文献
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木材微波干燥的应用与研究动态 总被引:3,自引:0,他引:3
分析了木材微波干燥的机理和优点,介绍了国内外木材微波干燥的研究与应用情况,指出木材微波干燥是一项具有广阔发展前景的新技术。建议今后加强木材微波干燥理论、干燥设备、干燥工艺、微波联合干燥技术等的研究工作。 相似文献
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《Drying Technology》2013,31(8):1527-1548
Abstract Microwave vacuum drying experiments were performed on a laboratory scale dryer with a two-level porosity material: a packed bed of porous alumina beads. The incident microwave power and the vacuum pressure level were fixed, the main varying parameters being the beads diameter and porosity, and the mean pore diameter. The drying kinetics and the evolution of the product temperature are presented. The drying kinetics can be divided into two main periods. The first one corresponds to the drying from the bed voids according to evaporation mechanism that we describe with a stagnant film law. The second one corresponds to the drying from the particle pores and we divide it into two parts: we suggest that the former is dominated by capillarity driven moisture transport, and the latter is limited by the desorption kinetics of the few water layers left. 相似文献
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Microwave vacuum drying experiments were performed on a laboratory scale dryer with a two-level porosity material: a packed bed of porous alumina beads. The incident microwave power and the vacuum pressure level were fixed, the main varying parameters being the beads diameter and porosity, and the mean pore diameter. The drying kinetics and the evolution of the product temperature are presented. The drying kinetics can be divided into two main periods. The first one corresponds to the drying from the bed voids according to evaporation mechanism that we describe with a stagnant film law. The second one corresponds to the drying from the particle pores and we divide it into two parts: we suggest that the former is dominated by capillarity driven moisture transport, and the latter is limited by the desorption kinetics of the few water layers left. 相似文献
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春笋微波干燥动力学模型研究 总被引:1,自引:0,他引:1
在不同微波功率下研究春笋(5mm厚度,200g)干燥过程中失水速率和颜色的变化规律。失水速率随微波功率增大而增大,用拟和性较好的Page方程建立了水分比变化模型。色泽变化参数用亮度L、红色度a和黄色度b表示。红色度a值和黄色度b值上升而亮度L下降,笋片微波干燥后总体色泽加深。色泽各参数变化用食品中零级和一级反应模型来拟和,其中L和b的变化适合一级反应模型,a的变化适合用零级反应模型表达。 相似文献
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In this work, the effects of power level and sample mass on moisture content, moisture ratio, drying rate, and drying time of Turkey okra (Hibiscus esculenta L.) were investigated using microwave drying technique. Various microwave power levels ranging from to 180 to 900 W were used for drying of 100 g of okra. To investigate the effect of sample mass on drying, the samples in the range of 25 to 100 g were dried at microwave power level of 360 W. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content. Among of the models proposed, Page's model gave a better fit for all drying conditions used. The activation energy for microwave drying of okra was calculated using an exponential expression based on Arrhenius equation and was found to be 5.54 W/g. 相似文献
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R. L. Passardi C. E. Schvezov M. E. Schmalko A. D. González 《Drying Technology》2013,31(11):1437-1442
Samples of Ilex paraguarienses were dried using microwave radiation at a laboratory scale. The sample temperature evolution and the moisture content rate were determined. The main results show that the process is viable and the product is acceptable for use. There is an advantage with respect to conventional drying since blanching and drying can be done in one step. The evaporation of free water for the experimental conditions is nearly uniform for leaves, twigs, and branches. The temperature during evaporation of the free water depends on the nature of the sample. 相似文献
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R. L. Passardi C. E. Schvezov M. E. Schmalko A. D. Gonz lez 《Drying Technology》2006,24(11):1437-1442
Samples of Ilex paraguarienses were dried using microwave radiation at a laboratory scale. The sample temperature evolution and the moisture content rate were determined. The main results show that the process is viable and the product is acceptable for use. There is an advantage with respect to conventional drying since blanching and drying can be done in one step. The evaporation of free water for the experimental conditions is nearly uniform for leaves, twigs, and branches. The temperature during evaporation of the free water depends on the nature of the sample. 相似文献
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M. Hemis 《Drying Technology》2014,32(5):543-549
The heat and mass transfer that occurred during drying of soybeans by a combined process using microwave (MW) and convective hot air was studied. A coupled mathematical model was developed to simulate this phenomenon. The soybean samples were re-wetted to 20% wet basis, the selected level of initial moisture content (IMC), and then dried in a domestic microwave oven under various MW power levels from 300 to 390 W, using inlet air with relative humidity of 35, 55, 75, and 95%. The simulated moisture loss profiles obtained from the coupled model compared well with those obtained in the experiments. Results showed that the drying rate decreased from 6.235 × 10?5 to 6.192 × 10?5 kg water/(kg wb s) as the inlet air temperature increased from 30 to 60°C. Furthermore, the drying rate was observed to increase from 6.192 × 10?5 to 6.211 × 10?5 kg water/(kg wb s) as the relative humidity (RH) increased from 35 to 95%. 相似文献
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Drying characteristics of Canada Western Red Spring (CWRS) wheat were studied using a domestic microwave convective oven. The effects of microwave power level, grain bed thickness, and initial grain moisture on the drying kinetics were investigated. Wheat samples with initial moisture levels of 0.18 to 0.29 kg water/kg of dry matter were dried for different drying periods of 180 to 360 s. The moisture loss data were recorded at regular short intervals. Then moisture loss data were fitted to various models (Page equation, modified drying equation, and Midilli equation) to study the drying kinetics of wheat. The results showed that wheat moisture loss increased with increasing microwave power level. A mathematical model was developed by coupling mass and energy balances, resulting in a system of non-linear equations. The predicted moisture loss data from the developed model were compared by fitting to experimental microwave data that were in good agreement. 相似文献
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Teresa De Pilli Roma Giuliani Antonio Derossi Carla Severini 《Journal of the American Oil Chemists' Society》2008,85(9):827-834
The aim of this work was to evaluate and compare the effects of conventional (hot air) and microwave drying on the lipid oxidation
of stuffed pasta. Experiments were carried out on the pasta type ravioli dried by conventional and microwave treatments. Peroxide
values and induction times were evaluated for the oil extracted from the stuffing. Peroxide values of the lipid extracts for
the samples dried by conventional drying and microwave drying were similar (P-level = 0.51) and less than threshold acceptable value (25 mequiv O2/kg oil). The use of microwave processing could be a remarkable energy saving measure as well as a way of lowering production
costs without compromising product quality. 相似文献