用Weibull函数分析单粒莲子热风干燥的水分扩散系数和活化能

为了研究单粒莲子在不同温度(50、60、70、80、90℃)条件下热风干燥的干燥特性、水分扩散系数及活化能,利用Weibull函数及经验模型对单粒莲子干燥过程进行模拟分析。结果表明:Weibull函数和Midilli模型可以很好地拟合单粒莲子的热风干燥过程;尺度参数α随干燥温度的升高而减小(p0.05);干燥温度对形状参数β的影响较大(p0.05);计算得到干燥过程中估算的水分扩散系数为(8.79×10~(-9)~2.45×10~(-8))m~2/s,水分有效扩散系数为(4.73×10~(-10)~1.31×10~(-9))m~2/s,活化能为22.61 kJ/mol,水分扩散系数随温度的升高而增大。该研究为Weibull分布函数应用于莲子干燥提供参考。     

基于Weibull分布函数的浆板热风干燥特性

以未漂硫酸盐针叶木浆为干燥对象,研究了热风温度和风速对浆板干燥特性的影响。利用Weibull分布函数对浆板的干燥特性曲线进行了模拟,并建立热风温度、风速与模型中参数(尺度参数α、形状参数β)的定量关系。结果表明,Weibull分布函数可以很好地模拟浆板的热风干燥过程;模型的尺度参数α与热风温度和风速有关,并且随热风温度和风速的升高而降低;模型的形状参数β与热风风速有关,随热风风速的升高而降低;浆板热风干燥过程的估算水分扩散系数在2. 116×10-7～3. 251×10-7m2/s之间,干燥活化能为14. 8 kJ/mol。     

黄花菜热风干燥动力学与维生素C降解动力学研究

该文研究热风干燥温度(50、60、70℃和80℃)对黄花菜干燥动力学(水分比、干燥速率、有效扩散系数、活化能)和维生素C降解动力学的影响。结果表明,黄花菜的干燥以降速阶段为主,随干燥温度的升高干燥时间显著缩短,水分有效扩散系数(D_(eff))显著升高。水分扩散活化能(E_a)与水分含量(M)呈指数关系:E_a=37.886 85exp(-M/1.739 28)+25.272 19。黄花菜干燥过程中维生素C降解呈Weibull模型,R~20.99,其降解的活化能(E_a)为72.25 kJ/mol。     

基于Weibull分布函数对猕猴桃切片中短波红外干燥过程模拟及应用

为了探究Weibull分布函数中各参数的影响因素及其在干燥中的应用,本试验以猕猴桃切片在不同的中短波红外干燥干燥温度(50、60、70、80℃)、干燥功率(675、1350、2025 W)条件下的干燥过程为研究对象,利用Weibull分布函数对其干燥动力学曲线进行模拟并分析。结果表明:Weibull分布函数能够很好地模拟猕猴桃切片的中短波红外干燥过程;尺度参数α与干燥温度和干燥功率均有关,并且随着干燥温度和红外功率的升高而降低;而干燥温度和红外功率对形状参数β的影响较小。通过计算求出干燥过程中的估算水分有效扩散系数,其值在1.06×10-7~3.51×10-7 m2/s范围内随着温度的升高而增大;通过阿伦尼乌斯方程计算出功率为675、1350和2025 W时,干燥活化能分别为32.55、27.02和28.07 kJ/mol。该研究为Weibull分布函数在猕猴桃中短波红外干燥技术的运用提供了技术依据。     

白萝卜间歇微波热风耦合干燥过程干燥特性分析

对比不同的间歇微波功率与热风耦合干燥及间歇微波干燥对白萝卜干燥特性（水分比、有效扩散系数和活化能）、中心与表面温度和颜色的影响。结果表明,有效扩散系数随水分含量的下降先缓慢上升后快速上升,活化能随水分含量的降低先缓慢升高后快速升高,Logistic模型能很好地反映活化能和水分之间的关系,并且单独进行间歇微波干燥的样品的活化能较高。干燥条件设定为间歇比5 s/20 s,热风温度30 ℃的样品其在干燥过程中物料中心温度最低,中心温度与物料表面温度相差最少,且干燥产品颜色最好。     

基于Weibull分布函数的枸杞微波干燥过程模拟及应用

为了探究Weibull分布函数中各参数的影响因素及其在枸杞微波热风联合干燥中的应用,以枸杞在不同脉冲比(脉冲比1.5:2 min/1 min;脉冲比1.67:3 min/2 min;脉冲比2:1 min/1 min)、微波功率(185、200、215 W)、微波介入时枸杞含水率(30%,40%,50%)条件下的干燥过程为研究对象,利用Weibull分布函数对其干燥动力学曲线进行模拟并通过建立的Weibull模型对枸杞微波干燥过程中的水分有效扩散系数和干燥活化能进行分析。实验表明:Weibull分布函数能够较好地模拟枸杞的微波干燥过程;尺度参数α与微波脉冲比、微波功率以及含水率均有关,并且随着微波功率的升高而降低,随着微波脉冲比和含水率的升高而升高;而初始含水率、脉冲比和微波功率对形状参数β的影响较小;根据Weibull分布含水分析得到枸杞的水分有效扩散系数为1.7×10~(-5)~3.2×10~(-5)m~2/h以及枸杞的干燥活化能为54.78 k J/mol。     

马铃薯片热风干燥特性及收缩动力学模型

为提高马铃薯片的热风干燥效率及品质,控制其干燥过程中的收缩变形,本文研究了不同热风温度（45、55、65、75 ℃）和切片厚度（3、5、7、9 mm）对马铃薯片热风干燥特性曲线、有效水分扩散系数及活化能等指标的影响。结果表明,干燥室内热风温度越高、马铃薯切片厚度越小时,干燥速率越快。在研究范围内,马铃薯片的有效水分扩散系数在5.02×10?10~11.53×10?10 m2/s范围内,其值随热风温度升高或切片厚度减小而增大。此外,研究发现Weibull分布函数能够很好地描述马铃薯片的降速干燥过程和收缩动力学模型。通过Arrhenius方程计算得到马铃薯片的干燥活化能和收缩活化能分别为27.35和46.44 kJ/mol,马铃薯片干燥比收缩消耗活化能少。本研究为马铃薯片在热风干燥加工中水分迁移和体积收缩变化的预测提供了理论依据和技术支撑。     

枸杞热风干燥过程动力学模型及品质分析

研究了不同温度(40,50,60℃)、不同预处理方式(直接干燥或Na2CO3溶液预处理)对枸杞热风干燥动力学、干燥过程颜色及干制品产品品质的影响。结果表明,Weibull分布函数能很好地模拟枸杞的热风干燥过程,尺度参数ɑ随温度升高而降低。在相同的温度下,经碱液处理的枸杞所对应的ɑ值要高于未经过碱液处理的样品,ɑ对应时间为整个干燥过程完成所需时间的(37.62±0.01)%,所对应水分比为0.382±0.001。直接干燥和经碱液处理的枸杞的形状参数β均大于1。随温度升高,估算水分扩散系数Dcal及有效扩散系数Deff均增大。直接干燥和经过碱液处理干燥的枸杞的活化能分别是50.71 k J/mol及49.65 k J/mol。直接干燥和经过碱液处理干燥的枸杞的颜色变化趋势不同,样品转折点均在1.0 g H2O/g干基。低温(40和50℃)条件下,经碱液处理的枸杞干制品颜色保持较好,总酚、总酮含量及·DPPH清除能力较高。     

黄芪切片热风干燥特性及动力学模型研究

分别研究热风温度(40,50,60℃)、风速(0.4,0.8,1.2m/s)和切片厚度(3,6,9mm)对黄芪切片热风干燥曲线、有效水分扩散系数、复水比和色差的影响,利用Weibull分布函数对试验数据进行拟合,并计算黄芪切片热风干燥活化能。结果表明:黄芪切片热风干燥属于降速干燥过程,热风温度和切片厚度对干燥时间影响较大,干燥过程服从Weibull分布函数(R~2=0.995 1~0.999 2);有效水分扩散系数为0.321×10~(-7)~1.178×10~(-7) m~2/s,热风温度和切片厚度对其影响较大,呈正相关性;干燥活化能为56.49kJ/mol,说明干燥操作较易实现;黄芪切片干制品复水比为2.02~2.43,随热风温度的升高而减小,随切片厚度的增加而增大;色差为1.96~7.01,随热风温度和风速的增加而增大,随切片厚度的增加而减小。     

基于Weibull分布函数的超声强化热风干燥紫薯的干燥特性及过程模拟

为探讨直触式超声对热风干燥过程的强化效果,以紫薯为干燥试材,利用超声热风干燥设备,研究不同干燥温度(40、50、60、70℃)及不同超声功率(0、30、60 W)条件下,紫薯片的干燥特性和品质变化规律,并利用Weibull函数对干燥过程进行了动力学模拟。结果表明:随着干燥温度的升高和超声波功率的增加,干燥时间明显缩短,干燥速率显著提高;Weibull分布函数可实现较高的模型精度;尺度参数α范围在92.317~345.764 min之间,且随着干燥温度升高和超声功率增大而减小,形状参数β在0.817~1.032之间,表明超声强化热风干燥紫薯的干燥过程由内部扩散阻力控制;水分扩散系数D_(cal)的范围为1.205×10~(-10)~4.513×10~(-10) m~2/s,其值随干燥温度和超声功率的升高而增大;干燥活化能随着超声功率的增加而相应减少;在相同超声功率下,随着干燥温度升高,总酚和总黄酮含量基本呈现先升高后下降的趋势;在较低干燥温度条件下,增大超声功率有利于提高总酚和总黄酮含量,但在较高温度条件下,增大超声功率则不利于总酚和总黄酮成分的保持。将超声技术用于热风干燥过程的强化可有效提高干燥速率和干燥品质。     

黔产皂角米多糖提取动力学及抗氧化活性研究

目的:以皂角米为原料,研究皂角米多糖的提取动力学及其抗氧化活性.方法:以Fick第一定律为基础,建立皂角米多糖的提取动力学模型,采用红外光谱对皂角米多糖进行结构分析,通过测定皂角米多糖对ABTS自由基、羟基自由基、1,1-二苯基-2-三硝基苯肼(DPPH)自由基、超氧阴离子自由基的清除能力来评价其抗氧化活性.结果:建立...     

香椿芽热泵式冷风干燥模型及干燥品质

为获得干燥速率快、品质高的香椿芽制品,以新鲜香椿芽为原料对其进行冷风干燥处理,研究不同干燥条件下香椿芽的干燥特性;采用Weibull函数模型对干燥曲线进行拟合并分析干燥过程;以干燥时间、干燥能耗、叶绿素含量、VC含量以及复水率为指标对不同条件下香椿芽冷风干燥过程进行加权综合评价;以热风干燥和真空冷冻干燥为参照,对比研究较优冷风干燥参数下香椿芽干制品的品质。结果表明,提升干燥温度、进口风速以及减少装载厚度均能显著减少香椿芽冷风干燥耗时（P＜0.05）,不同干燥条件对干燥耗时的影响程度由大到小为：温度＞进口风速＞装载厚度;Weibull函数模型能够准确描述香椿芽冷风干燥过程中水分含量变化过程（R2＞0.9）,其形状参数均小于1,整个干燥过程为降速干燥,主要由内部水分扩散控制;香椿芽冷风干燥有效水分扩散系数在（6.272～9.637）×10－9 m2/s之间,均属于10－9数量级,且受温度的影响最大;当干燥温度、装载厚度和进口风速分别为20 ℃、3.0 mm、2 m/s时,香椿芽冷风干燥的综合评分值最高,实验范围内,该条件较适合应用于香椿芽的冷风干燥中;相对于热风干燥而言,冷风干燥产品的品质更接近真空冷冻干燥产品的品质。     

百合热风薄层干燥特性及干燥品质

为提高规模化生产的百合品质,缩短干燥周期,以兰州百合为试样,运用JK-LB1700型薄层干燥试验台制干。系统研究了不同热风温度(60,70,80,90℃),热风速度(0.5,1.0,1.5,2.0m/s)和湿度(20%,30%,40%)对百合热风薄层干燥速率、色泽ΔE*值、VC含量、复水比的影响及各指标的变化规律;通过Weibull分布函数模拟了百合干燥过程及水分扩散规律。结果表明:随热风温度、热风速度增大百合热风薄层干燥时间显著缩短(P<0.01),不同相对湿度下无差异,但在干燥前期湿度大小与物料干燥速率呈正相关,后期呈负相关。采用Weibull分布函数能够准确(R2>0.99)描述百合热风薄层干燥过程,基于Weibull分布函数可准确获得百合薄层干燥水分有效扩散系数(1.213×10-6~3.992×10-6 m2/s),Deff值不仅受干燥参数影响,也受干燥设备和试样贮存时间的影响。试验干燥参数对百合品质指标色泽ΔE*值、VC含量和复水比的综合影响大小依次为干燥温度>热风速度>相对湿度,品质指标色泽ΔE*值和VC含量受干燥参数影响较大,复水比较小。     

油莎豆热风干燥特性及数学模型研究

以新鲜油莎豆为原料,研究风温和风速对油莎豆热风干燥特性的影响,计算干燥过程中有效扩散系数与活化能,并选取8种干燥动力学模型进行拟合分析。实验结果表明：热风温度越高,干燥速率越快,干燥时间越短;风速对干燥速率影响较小。本试验干燥过程主要发生在降速阶段,油莎豆有效水分扩散系数2.2856×10^-10～7.8112×10^-10,平均活化能为35.31kJ/mol,Two-term模型可以很好的反映油莎豆热风干燥过程,实验值与预测值吻合度较高,拟合效果良好。     

Modelling of red abalone (Haliotis rufescens) slices drying process: Effect of osmotic dehydration under high pressure as a pretreatment

Simultaneous application of osmotic dehydration and high pressure as a pretreatment to drying process on red abalone (Haliotis rufescens) slices was studied. During drying process the process time was reduced by increasing temperature from 40 to 60 °C along with the application of different pretreatments: high pressure (350 and 550 MPa), pressure time (5 and 10 min), and osmotic solution (10 and 15% NaCl). Effective moisture diffusivity was determined and varied from 4.35 to 9.95 × 10^− 9 m²/s, for both control and pretreated samples (R² ≥ 0.97). The Weibull, Logarithmic and Midilli–Kucuk models were applied to drying experimental data, where Midilli–Kucuk model was found to be the best fitting model. Furthermore, all drying curves were normalized and then modelled by the same three above models showing a R² ≥ 0.96. As to energy consumption and efficiency values for drying processes were found to be in the range of 777–1815 kJ/kg and 8.22–19.20%, respectively. Thus, knowledge on moisture transfer kinetics, energy consumption and data normalization, is needed to manage and control efficiently drying process under different pretreatment conditions.Industrial relevanceThis article deals with the mass transfer modelling and energy consumption during simultaneous high hydrostatic pressure treatment and osmotic dehydration as a pretreatment to drying process of abalone slices. Water and salt transfer during this combined process was satisfactorily simulated with the Midilli–Kucuk model. Results indicated that application of this combined innovative technology improved abalone slices dehydration rates compared to atmospheric pressure operation resulting in a dried abalone with intermediate moisture content ready to be used as input material of further processes. Furthermore, the different energetic features were determined in order to realize the importance of the changes that can influence to alter process time.     

Effect of ethyl oleate on drying characteristics of mulberries

In this study, air-drying experiments in thin layers of mulberry grown in Istanbul, Turkey, were conducted. The effect of ethyl oleate solution on drying time of mulberry samples was investigated in a pilot air-dryer. When ethyl oleate was used as pretreatment solution, the drying time of samples was decreased. Drying curves were obtained using the Page model. The effective diffusivity varied from 2.326 x 10(-10) to 1.809 x 10(-9) m2/s the temperature range. The temperature dependence of the diffusivity coefficient was described by the Arrhenius type relationship. The activation energy for moisture diffusion was found to be 50.87 kJ/mol for treated samples and 51.85 kJ/mol for untreated samples.     

Effect of ultrasound on banana cv Pacovan drying kinetics

The aim of this work was to study and to model the drying kinetics of fresh and ultrasonic pretreated banana cv Pacovan using the diffusional model (Fick’s second law) and an empirical two parameters model (Page model). The pretreatment was carried out in an ultrasonic bath at 30 °C. The drying process was carried out in a fixed bed dryer at two different temperatures (50 and 70 °C) and 3.0 m/s air velocity. Page empirical model provided the best simulation of the drying curves. The diffusional model was used to describe the moisture transfer and the effective diffusivities of water were determined and were in the order of 10⁻⁹ m²/s. These diffusivities increased with increasing temperature and with the application of ultrasound, while the process time reduced, which can represent an economy of energy, since air drying is cost intensive.     

Experimental study on drying of pear slices in a convective dryer

The experiments were conducted on pear slices with thickness of 5 mm at temperatures of 50, 57, 64 and 71 °C with an air velocity of 2.0 m s^?1. Prior to drying, pear slices were pretreated with citric acid solution (0.5% w/w, 1 min, 20 °C) or blanched in hot water (1 min, 85 °C). Also, the untreated samples were dried as control. The shortest drying time of pear slices was obtained with pretreatment with citric acid solution. It was observed that whole drying process of pear slices took place in a falling rate period. Four mathematical models were tested to fit drying data of pear slices. According to the statistical criteria (R², χ² and RMSE), the Midilli et al. model was found to be the best model to describe the drying behaviour of pear slices. The effective diffusivity of moisture transfer during drying process varied between 8.56 × 10^?11 and 2.25 × 10^?10 m² s^?1, while the activation energy of moisture diffusion in pear slices was found to be 34.95–41.00 kJ mol^?1.     

Impact of different pretreatment methods on drying characteristics and microstructure of goji berry under electrohydrodynamic (EHD) drying process

The aim is to find better pretreatment method to improve the drying speed of goji berry under electrohydrodynamic (EHD) drying process. The drying characteristics and microstructure of goji berry using different pretreatment methods under EHD drying process were investigated. The results showed that the drying rate after pretreatment was significantly higher than those of non-pretreated goji berry, and the different pretreatment methods had different effects on the drying characteristics of goji berry in an EHD drying system. The effects of different pretreatment methods on effective moisture diffusion coefficient were listed in descending order as follows: KOH > NaOH > Na₂CO₃ > ultrasonic > sucrose ester. The pretreatment has a great influence on the rehydration rate, specific energy consumption and microstructure of goji berry dried by EHD. Two index sequence analysis of infrared spectroscopy during goji berries drying process were established. The difference among five pretreatment methods was analyzed.