基于电场分布的单波导矩形微波喷动床结构设计

针对矩形微波喷动床,基于喷动腔内电场强度及电场分布均匀性进行结构分析与优化。采用的评价指标为反映电场分布均匀性的变异系数COV、平均电场强度E_(mean)和反映电场局部集聚参数E_(max)/E_(mean)。利用多物理场耦合软件COMSOL Multiphysics对喷动腔内电场强度进行数值模拟,通过单因素和正交试验法分别分析喷动床结构参数a(喷动床宽)、H(波导位置)和L(喷动床高)对评价指标的影响。结果发现,a对COV和E_(max)/E_(mean)的影响最显著,H对E_(mean)的影响最显著;a与L的交互作用对COV,E_(mean)和E_(max)/E_(mean)的影响均显著。单波导矩形微波喷动床的优化结构为:a=427mm,H=200mm,L=1 000mm。     

红外喷动床数值模拟中两种湍流模型的适用性

目的:得到适合红外联合喷动床数值模拟的湍流模型。方法:采用两方程模型(SST k-ε与Realizable k-ε)进行数值模拟,分析不同工况下红外喷动床的性能参数以及干燥室流场的流速、温度及颗粒浓度分布情况,并进行红外喷动床物料颗粒干燥试验。结果:在红外喷动床干燥室进气速度为8 m/s,温度为50℃的工况下,采用Realizable k-ε进行模拟得到的数值和SST k-ε的相近;采用两种湍流模型进行数值模拟得到的干燥室流体域中颗粒体积分数分布、速度分布及温度分布具有相似性,总体效果较好,说明这两种湍流模型应用于该设备均是可行的。但Realizable k-ε湍流模型的收敛速度更快,SST k-ε稳定性更好。结论:选择Realizable k-ε湍流模型进行红外喷动床的三维流场描述更加合理。     

喷动床在农产品干燥中的研究进展

农产品干燥是农产品加工业中一项非常重要的技术,为农产品原料的利用和新产品的开发提供了更多可能.能效和干燥产品的质量是农产品干燥的2个关键指标,喷动床干燥技术是这2个关键指标的有效提高途径之一.该文简述了喷动床技术在干燥农产品的应用中的研究进展,介绍了喷动床的结构、工作原理及其应用现状,分析了喷动床干燥农产品主要的优缺点...     

香菇红外喷动床干燥品质表征及呈味物质动态变化

该研究采用红外喷动床干燥香菇,研究其在不同出风风温(45、50、55、60℃)和风速(7.0、7.5、8.0、8.5 m/s)下的品质(色泽、粗多糖含量、单位能耗、微观结构、收缩率、复水比和质构特性)及在最佳干燥条件下呈味物质[5′-核苷酸、游离氨基酸和等鲜浓度(equivalent umami concentration, EUC)]的动态变化。结果表明,提高出风风温及风速能加快干燥速率,缩短干燥时间,降低单位能耗,样品蜂窝状结构更为均匀。综合对比得出,最佳干燥条件为出风风温55℃、出风风速8.0 m/s,在该条件下,L^*值和ΔE值分别取得最大值86.45和3.84,粗多糖含量取得最大值9.60 mg/g,单位能耗取得最小值98.74 kJ/g,微孔分布均匀,收缩率和复水比分别为81.43%和3.85,质构特性较好。在最佳干燥条件下,5′-核苷酸、Asp、Glu和Ser含量在干燥过程中持续增加(P<0.05),其余游离氨基酸含量及EUC值先增加后降低,游离氨基酸总量和EUC值分别在120 min和160 min时取得最大值110.02 mg/g和303.8...     

新型旋转导向管喷动床结构特征及流体力学特性

为研究"新型旋转导向管喷动床"的性能,采用油菜籽为原料,进行了流体动力学试验.考察了压降与风速、起喷压降与导喷距、不同导喷距下喷动量与风量、正常喷动时不同导喷距下压降与风量、喷动量与加料量及压降与加料量关系.结果表明,旋转导向管喷动床风速从0增大的过程中.压降会出现一个峰值,且从导喷距40mm 的1.50 kPa增大到80mm 时的14.43 kPa;导喷距对喷动量的大小及随风量的变化趋势有较大影响,并且导喷距在45～75 mm、风量57～105 m3/h的范围内,喷动量随风量增大而增大,且其变化范围是5.21～10.28 kg/min,而导喷距为80 mm时喷动量会在风量99 m3/h时出现最大值8.84 kg/min,对应的操作压降也有类似的规律;加料量增大,喷动量和压降都增大,在风量90 m3/h、加料量为5～20 kg的条件下,导喷距为50和80mm 时的喷动量和操作压降的变化范围分别是7.97～9.09 kg/min和1.37～1.49 kPa及7.02～10.24 kg/min和1.41～1.73 kPa.     

高丽菜脉冲喷动床-低频微波干燥品质与能耗

为解决调理蔬菜热风干燥(AD)产品粘连、品质差、能耗高及高污染等问题,以高丽菜为实验原料,利用常压脉冲喷动床-低频微波干燥(PSBLMD)中试平台,进行调理高丽菜PSBLMD品质、均匀度及能耗研究,并与AD方式进行对比分析。结果表明,PSBLMD调理高丽菜(加糖比例15%)抗坏血酸质量浓度、叶绿素质量浓度及复水比(4.69 mg/hg、3.48 mg/hg、26.22)均高于AD高丽菜相应值(1.46 mg/hg、3.14 mg/hg、19.40),PSBLMD样品的水分、色差及收缩率均匀度(91.2%、93.7%、92.3%)达到90%以上;与AD方式相比,PSBLMD不但可以有效解决高糖调理高丽菜干燥过程产品粘结问题,提升干燥产品品质,而且缩短干燥周期50%以上且降低能耗40%以上。     

喷动床最小喷动速度的计算颗粒流体力学数值模拟

为了进一步研究喷动床的操作参数和结构参数对最小喷动速度Ums的影响,以及建立最小喷动速度的预测关联式,课题组建立了二维喷动床数理模型,床的高度为800 mm、宽度为200 mm和厚度为20 mm,喷动气入口底部是夹角为60°的V形结构。采用计算颗粒流体力学(CPFD)方法模拟计算了5种颗粒在3种喷口宽度和在不同静止床高时最小喷动速度变化情况。结果表明:喷动床的结构参数和操作参数对最小喷动速度有着极大的影响,最小喷动速度随着静止床高和颗粒粒径增大而增大,而随着喷口宽度的增大而减小;综合所有数据进行多因素影响回归,得到了新的最小喷动速度预测关联式。研究结果对于喷动床实际操作条件的确定和工艺设计提供了借鉴。     

咖啡豆红外喷动床干燥对其粉末物性品质、干燥能耗及挥发性成分的影响

为获得高品质干燥咖啡豆,采用红外喷动床组合干燥技术对咖啡豆进行干燥处理,研究不同进口温度和进口风速对咖啡粉色泽、堆积密度、休止角、得粉率、持水能力和水溶性指数、微观结构、干燥能耗及挥发性成分的影响。结果表明,提高进口温度和进口风速可以加快干燥速率,缩短干燥时间,降低干燥能耗。采用顶空固相微萃取-气相色谱质谱联用共检测出7大类(酸类、酯类、醛类、醇类、酮类、杂环类及其他类)挥发性化合物,其中酸类、酯类、醇类、杂环类4类为咖啡豆主要挥发性化合物且含量较高。综合对比得出最佳干燥条件为进口温度75℃,进口风速7.5 m/s,在此条件下,L^*值和堆积密度取得最大值,分别为106.59和0.65 g/mL,休止角取得最小值36.87°,得粉率、持水能力和水溶性指数取得最大值,分别为43.43%、5.4 g/g和41.27%,干燥能耗取得最小值336.53 kJ/g,形态结构保存较为完整,壁面光滑平整,检测到的挥发性成分种类最高达70种,含量为38 487.028 49 ng/g(以干基计),咖啡豆综合品质最佳。该研究可为红外喷动床干燥技术在咖啡豆干燥加工及工业化生产中的应用提...     

新型旋转导向管喷动床结构与力学特性实验研究

用油菜籽为原料,对"新型旋转导向管喷动床"进行流体动力学实验。考察了压降与风速、起喷压降与导喷距、不同导喷距下喷动量与风量、正常喷动时不同导喷距下压降与风量、喷动量与加料量及压降与加料量关系。结果表明,导喷距对喷动量的大小及随风量的变化趋势有较大影响,并且导喷距在(45～75)mm、风量(57～105)m~3/h的范围内,喷动量随风量增大而增大,而导喷距为80mm时喷动量会在风量99m~3/h时出现最大值8.84 kg/min,对应的操作压降也有类似的规律;加料量增大,喷动量和压降都增大。     

脉冲喷动床微波冻干方便面品质与能耗研究

以湿面条为实验原料,进行脉冲喷动床微波冻干(PSBMFD)面饼品质与能耗研究,并与传统电加热冻干(CFD)方式进行对比分析。研究表明:PSBMFD面饼的复水时间、复水比及复水前后硬度值分别为150 s、3.07、4 692.36 g、520.45 g,水分、色差及收缩率的均匀度分别为94.51%、94.31%、92.23%,感观评价总分为8.2,干燥时间为3.5 h,干燥产品总耗能为8.05 kWh/kg。PSBMFD技术不仅提高冻干面饼的干燥均匀度,改善冻干面饼的品质,而且与CFD相比,能够明显地缩短冻干时间(58.83%),降低冻干能耗(66.63%)。     

Experimental and parametric study on drying of green peas in spouted bed

Drying of Green Peas (Pisum sativum) was studied experimentally in a lab‐scale spouted bed. Experiments were carried out at different operating conditions, and the effect of inlet air temperature and its flow rate, bed height (initial mass of wet particles) and average diameter of particles were examined on performance of dryer and rate of drying. The obtained experimental results were fitted by an exponential form equation to model the drying kinetic behaviour of green peas in a spouted bed. The fitting parameters are presented in the form of mathematical correlations as a function of operating parameters. As expected, it was found that by increasing inlet air temperature and air‐flow rate, the rate of drying increases, but by increasing the bed height and diameter of particles, the rate of drying decreases. The results can help the design engineers to choose the optimum drying conditions for industrial applications.     

Image analysis and quality attributes of malting barley grain dried with infrared radiation and in a spouted bed

The impact of drying two spring barley cultivars (Mauritia and Prestige) in a spouted‐bed and in infrared radiation (IR) dryers on grain dimensions, colour, pigment content, vitality and malt quality was investigated. The results indicate that the investigated drying methods led to kernel dimension changes. Kernel shrinkage was typical of spouted bed drying, while kernel expansion was observed after IR drying at the intensity of 900 W m^?2. An increase in the intensity of yellowness (b*) on the surface of dried grain and a decrease in the yellowness intensity of kernel cross‐section were also observed. The aforementioned changes were associated with the decomposition of carotenoids (endosperm colour) and reduction of soluble proanthocyanidin and total phenolic compounds (surface colour). The drying processes also lowered germination energy and capacity, in addition to susceptibility to moisture diffusion into the endosperm. These adverse results were cultivar dependent and affected the quality of malt and wort only to a limited extent. The main changes were an increase in the Kolbach index in malt from Mauritia cv., and a fluctuation of the diastatic power of malt that did not exceed ±3%. Generally, drying of barley grain in spouted bed should be conducted at an inlet air temperature of 40 °C and using an IR drier at a radiation intensity of 600 W m^?2.     

Effect of constant and variable temperature drying processes on drying characteristics,quality, and volatile profile of rose petals in infrared-assisted spouted bed drying

The edible rose (Rosa Crimson Glory) petals were dried using infrared-assisted spouted bed drying technology. The effects of different drying temperature conditions (30, 35, 40, 45, and 50°C, as well as stepped heating drying [SHD] and stepped cooling drying) on the drying characteristics, physicochemical properties, antioxidant capacity, and changes in volatile flavor compounds of the rose petals were investigated. The results showed that the drying time was shortened with increasing drying temperature. Both variable temperature drying processes gave the shortest drying times. Optimal color retention of rose petals was achieved at a constant temperature of 40°C and SHD. Increased drying temperature resulted in higher water-soluble polysaccharide content in the dried rose petals, whereas lower temperatures facilitated anthocyanin preservation. The variable temperature drying processes favored the retention of water-soluble polysaccharides in rose petals, but not anthocyanins. Regarding antioxidant capacity, the samples dried at 40°C and those subjected to the two variable temperature drying processes performed better. This study also analyzed the differences in volatile flavor compounds of rose petals dried under different drying conditions. It was found that the majority of volatile flavor compounds in the rose petals dried by SHD exhibited higher content levels than the other drying conditions. Therefore, considering a thorough evaluation of all relevant factors, it was clear that utilizing the SHD process was the most efficient method for obtaining the best quality rose petals overall.     

猕猴桃切片流化床干燥特性与干燥动力学模型研究

为了提高猕猴桃切片制干品质、缩短干燥时间,采用流化床干燥技术对其进行干燥,研究温度(55,65,75,85℃)、风速(1.5,2.5,3.5,4.5m/s)和厚度(5,10,15mm)对猕猴桃切片热风干燥曲线、水分有效扩散系数以及干燥活化能的影响.结果表明:猕猴桃切片的整个干燥过程属于降速干燥,水分有效扩散系数为1.2...     

间歇流化床干燥胡萝卜的研究

采用间歇流化床干燥胡萝卜 ,考察和分析了气体流量、进气温度、床层载荷、物料粒径以及烫漂预处理对干燥速率、产品质量及能量利用效率的影响 ,并对影响的过程和机理进行了详细的分析     

Performance analysis of deep bed drying of canola seeds using numerical technique

Canola grain containing 18–20% moisture during harvesting is not suitable for safe storage. The storage conditions for these grains need to be optimized through drying technique to prevent both fungal attack and suppression in germination. Hence, the present investigation has been carried out to analyze coupled heat and mass transfer phenomena during steady state counter flow deep bed drying. To carry out this study, a non-equilibrium drying model has been developed. Governing equations include moisture mass balance, enthalpy balance, heat transfer rate, mass transfer rate for an element along bed height. And diffusion equation of moisture inside a single kernel has also been solved simultaneously through an implicit scheme using TDMA (Tri-Diagonal Matrix Algorithm). An iterative approach has been used to solve the governing equations for a selected geometry of the dryer. The rating analysis can be used for arriving at improved quality and higher efficiency at reasonable level of throughput.