基于BP算法的喷雾干燥神经网络模型的建立

随着经济的发展，喷雾干燥技术的应用越来越广泛，但在实际生产实践中．由于干燥过程影响因素很多，喷雾干燥的参数调试和试验必须在实际试验中探索。为此，通过搜集大量相关资料，选择了3个对喷雾干燥效果影响较大的参数（进风温度、压力、粘度）作为输入。选择平均粒子径参数来反映喷雾干燥的效果。建立三输入单输出的BP神经网络模型来模拟喷雾干燥系统的干燥机理，从而在计算机上实现了实时监测与控制相关参数对喷雾干燥过程的影响。实验证明，其对指导生产试验与降低经济成本具有一定意义与价值。     

脉动气流的喷雾干燥

利用脉动燃烧器产生的高频脉动尾气流对NaCl溶液进行了喷雾干燥试验，应用激光粒度分析仪（PDA）和激光速度分析仪（LDA）等测试装置对干燥器内的液滴粒度、速度和温度分布进行了在线测量，并对其干燥过程进行了分析。试验结果表明，高温、高频振荡气流下的喷雾干燥的蒸发速率提高2.5倍。     

我国农产品干燥装备技术与发展趋势

干燥技术是农产品加工过程中最重要的因素,其对农产品产后处理有着重要的影响。主要介绍了自然干燥、微波真空干燥、射频干燥、热风微波干燥、太阳能干燥、真空冷冻干燥、膨化干燥、热泵干燥、滚筒干燥、喷雾干燥和折射窗干燥等技术与应用,分析了各种干燥技术的优缺点,对农产品在节能、自动化、标准化和联合干燥方面做出了发展展望。      

地黄真空红外辐射干燥质热传递分析

以Fourier方程和Fick定律为基础,建立了地黄真空红外辐射干燥过程传热、传质的数学模型.通过理论推导和试验测定,确定了模型中有关参数的数值或方程.利用有限差分法进行了不同干燥条件下物料温度和含水率变化的数值模拟.结果表明:模拟值和试验值吻合较好,该模型可以较好地拟合地黄干燥过程中温度和含水率的变化,且能较好体现各干燥参数对干燥特性的影响情况.     

亚麻胶的提取及应用研究进展

综述了亚麻胶在提取、干燥和应用上的研究进展。亚麻胶的提取原料有亚麻籽、亚麻粕和亚麻壳,其干燥方式主要是喷雾干燥,它主要用于食品、日用化工和制药等行业。      

喷雾干燥法技术特征与发展趋势

基于喷雾干燥法基本工作原理与特点,对喷雾干燥法应用发展及作用机理进行深入探析,对喷雾干燥法目前在农业生产中的应用发展进行概述,最后分析了其存在的局限性和未来的发展方向。研究结果可以为干燥技术的发展提供参考和借鉴。     

基于BP神经网络的牡丹花热风干燥含水率预测模型

针对热风干燥制作牡丹压花时含水率不便实时测定的问题,探讨了干燥过程中热风温度、风速、压花板孔密度和牡丹花初始质量对干燥速率的影响.利用BP神经网络建立了干燥时间、热风温度、风速、牡丹花初始质量、压花板孔密度与牡丹花干燥过程中含水率之间的关系模型,采用Matlab神经网络工具箱对模型参数进行训练和模拟.结果表明,利用神经网络建立的模型仿真结果与实测值接近,预测性较好.     

折射窗干燥技术

折射窗干燥是一种传导、辐射和薄层干燥相结合的全新干燥技术,可用于替代传统的干燥方法来加工及干燥热敏性强的、不能采用喷雾干燥的浆体物料,在药品、果蔬粉和调味料等食品干燥加工领域有较大的应用潜力.为此,介绍了折射窗干燥技术的原理、设备结构特点及应用前景.     

苹果渣干燥特性与模型的试验研究

利用热风循环干燥试验台对苹果渣进行干燥试验,在不同初始水分、不同风速和不同温度下,对苹果渣干燥特性进行了试验研究。试验结果表明：初始水分、风速和温度对干燥速率有极显著作用;苹果渣干燥为一降速干燥过程。通过对干燥速率随时间变化关系的分析,提出了相应的干燥速率模型。用4种模型对干燥曲线进行了模拟,改良的Page模型很好地预测和描述了苹果渣热风循环干燥特性。     

涡旋混流式喷雾干燥塔的设计与计算

涡旋混流式喷雾干燥塔,由于塔内热风速度较大,且形成涡旋,故料液热交换充分,干燥强度大,热效率较高,适于植物淀粉、大豆蛋白、玉米浸出物等农产品干燥加工。设计合理的涡旋式干燥塔,对于开发农产品深加工无疑是非常有意义的。本文提供了并、逆流混合流动状态的涡旋上排风喷雾干燥塔的设计计算方法。     

Does partial root-zone drying improve irrigation water productivity in the field? A meta-analysis

Partial root-zone drying improves irrigation water productivity (IWP, yield per unit applied irrigation water) with respect to controls receiving substantially more water, but similar gains are often achieved with conventional deficit irrigation. This paper presents a meta-analysis of IWP for a broad range of horticultural crops and environments. Two comparisons were preformed: (a) crops managed with either partial root-zone drying or conventional deficit irrigation against controls receiving substantially more water than the two water-saving techniques, (b) crops managed with partial root-zone drying and their counterparts with conventional irrigation where both received similar amounts of irrigation. In relation to controls receiving substantially more water, conventional deficit irrigation increased IWP by an average 76% and partial root-zone drying by 82%; the gains from both water-saving methods were statistically undistinguishable. Yield per unit applied irrigation water of crops under partial root-zone drying was significantly (P = 0.007) but modestly (5%) higher than in their counterparts with conventional irrigation where both received similar amounts of irrigation. In 80% of cases the difference in IWP between the two methods was in the ±20% range. Considering the cost and management complexity of implementing partial root-zone drying, it is critical to identify the rare conditions where this method could be economically justified.     

Water use efficiency of controlled alternate irrigation on root-divided maize plants

A new method of irrigation was designed and tested for its water use efficiency (WUE). Maize plants were grown in pots with their roots divided and established into two or three separated containers of which irrigation and soil drying were controlled alternately. Results showed that when the two halves of the root system were alternatively exposed to a drying soil and a soil with its water content maintained above 55% or 65% of its field capacity, water consumption was reduced by 34.4–36.8% and the total biomass production was reduced by only 6–11%, when compared to the well-irrigated plants. Significant increase in WUE, root to shoot ratio and stomatal resistance for water diffusion were observed as a result of such treatment. Leaf transpiration was reduced substantially while the rate of photosynthesis and leaf water content were not significantly altered. The results were also compared to root-divided plants of which irrigation was fixed to one container only and showed that a better WUE, root development and distribution, shoot biomass production were achieved by the alternate drying and rewetting. We conclude that the controlled alternate irrigation (CAI) is an effective and water-saving irrigation method and may have the potential to be used in the field.     

热风干燥下半干面含水率变化规律

半干面作为一种新型面制品,具有口感好和保质期长等优点。脱水干燥是半干面生产过程中最重要的工序之一,干燥方式和条件的选择直接影响着半干面的品质。利用热风干燥方式设计的恒温恒湿干燥系统通过对温湿度及风速等参数的设置,具有良好的干燥效果。通过对1.0×570和1.5×360和1.7×510 3种规格半干面在不同干燥条件下进行脱水干燥,得出3种规格半干面的含水率变化曲线。经过数据对比与分析,可知在干燥时间为22 min左右时,每一种规格的半干面均能达到含水率要求（22%～26%）。结论表明:在相同干燥条件下,直径接近,长度较短的半干面达到含水率要求所需干燥时间较短。该试验通过探究半干面含水率变化规律,为半干面的生产提供了一定的参考意义。      

太阳能真空玻璃谷物干燥装置水势模型研究

在设计太阳能真空玻璃谷物干燥装置的基础上,对其干燥工艺流程进行分析,建立谷物内部水分的流动模型,对谷物干燥循环过程中谷物的含水率进行模拟计算,试验研究与分析表明,干燥9个循环时间后,谷物的含水率达到14.036 8%,在12个循环之后,谷物含水率下降到12.974 1%,之后很难继续降低含水率。干燥效率最佳,谷物在仓内干燥最佳时间为2.57 h。     

红外玉米穗干燥试验研究

为研究红外辐射干燥条件下收获期玉米穗干燥的水分迁移规律,利用自制红外玉米穗干燥试验台对玉米穗进行了恒温和变温干燥试验,探讨了多种温度条件下玉米穗的红外辐射干燥特性及对干燥后玉米穗外观品质的影响规律。结果表明:初始含水率、干燥温度、干燥用时和辐射距离是影响玉米穗干燥效率和外观品质的主要因素;当恒温干燥玉米穗的干燥温度为58℃、辐射距离为150mm时,干燥速率达2.25%/h,且玉米籽粒的外观品质最好;变温干燥玉米穗时,较佳的干燥温度范围为55~65℃,且采用逐渐升温干燥时的干燥品质较好。本研究为研制红外辐射玉米穗干燥机研发奠定了坚实基础。     

The Initial Phase of Convection Drying of Vegetables and Mushrooms and the Effect of Shrinkage

The results of measurements of loss of water in convection drying of slices of cut vegetables and mushrooms, not touching one another, indicate that the rate of drying of these products decreases from the beginning of the process. Consequently, almost all researchers have assumed that during the initial stage of drying, there is no stage of constant drying rate determined by conditions of external water exchange. Instead, it was assumed that models of the drying of these products from initial to final water content should be solutions of differential equations of internal mass diffusion or semi-empirical exponential equations. Such a view is not, however, compatible with the theory of convection drying of solids with high initial water content, such as vegetables and mushrooms. The results of studies presented in this paper, show that the initial stage of drying of red beet, onions, carrots, garlic and mushrooms, is a constant rate process determined by the known model of the theory of drying based on laws of external exchange of heat and water. Losses of water from 10 to 30% were compatible with the model, with a relative error of less than 1%, and from 40 to 50% with an error less than 5%. The introduction into the equation of a coefficient to allow for shrinkage of the products, extended the range of applicability of the model from 20 to 50% water loss with a relative error of less than 1%, and from 50 to 80% with an error of less than 5%.     

基于低场核磁的马铃薯切片干燥过程水分迁移规律研究

为研究马铃薯切片热泵干燥过程中内部水分迁移规律,利用低场核磁共振技术检测横向弛豫时间T2,分析峰面积A2x的变化,建立水分变化动力学模型。结果表明：热泵干燥过程中,提高热风温度能够显著提高干燥速率,加快结合水、不易流动水以及自由水的迁移。干燥过程中自由水和结合水先于不易流动水发生变化,自由水含量在前90min基本保持不变,之后迅速下降,不易流动水和结合水含量均表现为先升高后降低的趋势。自由水被脱除后,不易流动水和结合水依次达到最大值,随着干燥进行不易流动水逐渐被脱除,随后结合水开始被脱除至干燥结束。马铃薯切片热泵干燥过程属于内部扩散控制,水分有效扩散系数范围为5.228×10-8～1.434×10-7m2/s,建立的干燥动力学模型决定系数均大于0.98,可用于预测马铃薯切片干燥过程中不同状态的水分迁移规律。     

黑龙港地区土壤含水量的垂向分布研究

黑龙港地区是河北省为落实"2020年我国新增粮食500亿kg"的规划而划定的粮食主产区之一,土壤水的开发利用是未来粮食增产的重要措施。为探讨黑龙港地区土壤含水量垂向分布情况,以河北省农林科学院旱作农业研究所衡水试验站土壤为观测点,分别利用FDR、TDR、烘干法测量了不同深度的土壤含水量。结果表明在0~110cm深度上土壤含水量整体上呈现先增加后减少再增加的趋势,这种趋势主要是由于不同土层的不同性质所决定的,而土壤垂向剖面存在的两个潴育层是土壤水分含量呈现这种变化趋势的主要原因。     

新型卧式旋转干燥仓设计与优化

中国粮食干燥设备处于更新换代关键时期.在干燥过程中,干燥设备对粮食籽粒造成的机械损伤不容忽视.为克服传统粮食干燥设备对粮食品质造成的不利影响,本研究设计开发了一种新型卧式旋转干燥仓.该设备的特点是低温干燥,整仓缓慢旋转搅拌粮食,以保证粮食干燥后含水率的均一性,有效降低粮食干燥过程中的机械损伤,确保粮食干燥品质.本文详细...     

花生换向通风干燥性能模拟与分析

为了解固定床花生换向通风干燥作业特性,为已研发的箱式换向通风干燥设备提供合适的花生干燥通风参数,以花生与空气间的传热传质为基础,建立干燥状态偏微分方程组,并以此为基础采用有限差分法对干燥过程进行数学模拟,分析左右干燥室同时从下向上通风干燥时长、换向干燥阶段换向时间、单位体积通风量对干燥行为的影响,并采用均匀设计和综合加权评分法确定最优通风干燥参数。结果表明:从下向上通风阶段,热量主要用于花生加热和表层水分快速蒸发,下、中、上层物料干燥升温速度差明显,易形成较大水分梯度;换向通风干燥阶段,物料温度呈类波浪状波动,有效控制整床物料干燥均匀性。缩短从下向上通风时间,有助于降低耗能和水分差,但对干燥耗时和生产率影响较小;换向时间的改变对耗时、生产率、耗能、水分差影响较小;单位体积通风量的增加有助于干燥耗时、水分差的降低及生产率的提高,但耗能亦将快速增加。均匀设计和综合加权评分表明,含水率>25%阶段通风量1 394 m~3/(m~3h),含水率15%～25%阶段通风量838 m~3/(m~3h),含水率0.98,模拟仿真可准确描述干燥过程物料温度和含水率变化。为花生换向通风干燥设备改进和工艺优化提供参考。