核桃滚筒催化红外—热风干燥试验及能耗分析

为了提高硬壳坚果类产品干燥效率，在研制的滚筒式催化式红外干燥设备基础上进行核桃红外干燥试验，考察工艺参数对脱水率、颜色和开壳率的影响。将滚筒催化红外—热风联合干燥和单一热风干燥作比较，对二者的干燥时间、干燥曲线、干燥速率曲线和能耗进行对比分析。研究结果表明，催化红外温度、距离和滚筒转速均对干燥效果和产品品质有显著影响，先在最佳的距离30 cm、温度450 ℃、滚筒转速1.5 r/min条件下滚筒催化红外预干燥9.5 min，然后在温度43 ℃、风速3 m/s条件下热风干燥16 h，与单一热风干燥（20 h）相比，显著提高了干燥速率，缩短了19.2%的干燥时间，节约了11.6%的能耗，且干制核桃的品质良好。     

不同干燥工艺对南美白对虾仁品质的影响

以南美白对虾仁为实验原料,研究了热风干燥、微波干燥、热风联合微波喷动干燥和真空冷冻干燥对南美白对虾的影响,并且以干燥速率、复水率、色泽变化、质构以及脂肪氧化等指标进行比较。研究结果表明:真空冷冻干燥得到产品的品质最好,但是干燥时间是热风干燥的2.25倍,是微波干燥和热风联合微波干燥的9倍和10.3倍;热风联合干燥能够克服单一微波干燥的不均匀性,且干燥后样品的品质最接近于真空冷冻干燥,因此热风联合微波喷动干燥是一种具有发展前景的干燥方法。     

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。     

悬浮烘干机干燥系统设计的初步研究

悬浮烘干技术与喷动床烘干技术原理相象,都是用于粗大颗粒物料干燥的一种新型流化技术。本文采用内部加热和普通喷动床相结合的方式设计了悬浮干燥系统,物料在烘干过程中处于悬浮状态,实现了在烘干过程中以每颗被烘干物料个体为脱水量检测因子控制烘干质量和烘干时间,与传统喷动床相比,强化了传热传质,提高了热效率,减少了空气用量,降低了能量消耗。     

土豆片脉冲喷动微波负压干燥特性及品质

在干燥腔内真空压力范围为11.8~15.0 kPa的条件下,研究微波功率、脉冲喷动频率、预处理及不同组合方式对脉冲喷动微波负压干燥(PSMVD)土豆片的干燥特性及色泽、质构、均匀性等品质的影响。结果表明:Midilli传质薄片模型优于其它三个模型;未漂烫处理及提高微波功率可以增加土豆片在干燥过程中水分扩散系数Deff,从而缩短土豆片脉冲喷动微波负压干燥时间。与传统的干燥相比,脉冲喷动微波负压干燥具有干燥周期短、产品干燥均匀性及品质较好等优点。     

远红外联合低温真空干燥设备研究与设计

针对现有干燥设备存在的生产效率低,难以满足企业规模仅生产等缺陷的问题.在真空条件下,对干燥原理与方法进行研究,设计一套工业远红外联合干燥设备.文章介绍该设备的主要结构及其参数,通过能量衡算,确定热量的需求量和加热系统(红外管的参数)的布局.设计的干燥设备成本低、能量利用率高,预期可满足工业需求.     

核桃的变温滚筒催化红外-热风联合干燥研究

为了提高硬壳坚果类产品干燥效率,创新研制了一台新型多机组合式滚筒变温催化红外干燥设备,并采取变温滚筒催化红外-热风联合干燥技术,对核桃干燥效果、能耗和动力学过程进行了研究。研究表明,红外辐射温度、辐射距离和滚筒转速均对干燥效果有显著影响。在优选的最佳辐射温度300+400℃、辐射距离30 cm、滚筒转速25+35+35 Hz条件下催化红外预干燥22.50 min然后在温度43℃、风速3 m/s条件下热风干燥14 h,总干燥时长为14.38 h,与单一热风干燥(20 h)相比,干燥时长缩短了28.10%,且节约了25.04%的能耗,干制核桃表壳无褐斑,开壳率为0%,颜色指标L为54.24,a为10.61,b为19.89,呈较亮的红黄色。此外最大干燥速率0.28 g/(g·min)也显著高于单一热风的最大干燥速率0.11 g/(g·min)。相应的建立了用于预测其干燥过程中含水率以及干燥速率变化的Henderson-Pabis模型,R~2为0.99,RMSE为0.03,拟合效果良好。本研究得出变温滚筒催化红外-热风干燥是一种适宜硬壳坚果类产品干燥的新型高效节能方法。     

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及发展趋势,并提出了作者的一些建设性意见,为喷动床干燥技术在农产品干燥中应用的深入研究提供参考,为充分利用偏低能耗与低成本来获得高质量脱水干燥产品提供借鉴。     

两种不同干燥方式对不同预处理方式的脱盐鸭蛋清品质的影响

采用真空冷冻干燥和负压微波喷动干燥两种干燥方式,对经不同预处理的咸鸭蛋清进行干燥制粉,以鲜鸭蛋清为对照,研究不同干燥方式咸鸭蛋清脱盐前后的功能特性。产品的质量主要通过色差、表观密度、凝胶性、起泡性及泡沫稳定性、乳化性及乳化稳定性等方面来衡量。实验结果表明:当负压微波喷动干燥条件为干燥腔压力80 Pa,脉冲压力800 Pa,微波功率0.1~0.6 kW,每间隔10 min脉冲2 s;真空冷冻干燥条件为真空泵压力10 kPa,温度为50℃,加热功率为350 W,干燥时间为10 h时,负压微波喷动干燥产品的理化特性优于真空冷冻干燥产品的理化特性(色泽、表观密度值、硬度、起泡性和乳化性等),咸鸭蛋清的最佳干燥方式是负压微波喷动干燥(PSMFD);经超声波预处理后PSMFD的蛋清粉具有最好的色泽,较好的表观密度值(0.333 kg/dm3)、较小的硬度(831.251 g)、较高的起泡性(86.7%)和乳化性(0.540 4)、较好的起泡稳定性(93.3%)和乳化稳定性(26.48 min)。     

脉冲喷动微波真空干燥器内喷动流化动力特性的数值研究

为探索脉冲喷动微波真空干燥系统(PSMVD)中气固喷动流化床的动力特性,采用基于无粘性两相流理论,使用计算流体力学欧拉-欧拉方法(CFD)对二维喷动流化床中喷动流化特性进行了数值研究,对喷动流化床的动力特性和颗粒运动分布特征进行了揭示,这些因素影响颗粒空间位置分布和其微波加热的均匀性。结果表明,采用欧拉-欧拉双流体模型,成功获得脉冲喷动微波真空干燥腔内的二维喷动流化床的喷动流化动力特性;喷动流化过程在特定气流喷动速度下有一个初始阶段和准稳态流化阶段;喷动速度是控制颗粒在喷动床中颗粒位置的重要因素,存在一个影响流化模式转变的关键喷动速度;射流穿透深度和喷射速度之间存在线性关系。     

Microwave Finish Drying of Diced Apples in a Spouted Bed

The combination of a spouted bed with microwave heating to improve heating uniformity was evaluated. Experiments were performed on a laboratory system in which evaporated diced apples of about 24% moisture were dried to about 5% at 70°C air temperature using four levels of microwave power density (0 to 6.1 W/g). With the combination method, temperature uniformity in diced apples was greatly improved as compared to that with a stationary bed during microwave drying. Products had less discoloration and higher rehydration rates as compared to conventional hot air drying or spouted bed (SB) drying. Drying time could be reduced by >80% compared with SB drying without microwave heating.     

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%)。     

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.     

Studies on different combined microwave drying of carrot pieces

Three different combined microwave (MW) drying methods were compared, namely microwave‐assisted vacuum drying (MWVD), microwave‐assisted freeze drying (MWFD), microwave‐enhanced spouted bed drying (MWSD), in terms of drying rate, drying uniformity, product colour, rehydration ratio, retention of β‐carotene and vitamin C, and energy consumption. The drying rate of MWVD and MWSD were much faster than that of MWFD. The largest drying rate was obtained in MWSD with 3.5 W g^?1. In general, the colour of MWSD products was very uniform. Rehydration ratio of MWFD carrot pieces was almost the same as the freeze‐dried (FD) products and better than MWVD and MWSD products. In addition, the highest retention of carotene and vitamin C was observed in MWFD carrot pieces. No significant differences were observed in carotene and vitamin C between MWVD and MWSD products. However, the energy consumption in MWFD was the highest.     

响应面法优化香菇热风-微波联合干燥工艺

本文基于热风-微波分段联合干燥方式,探讨了联合干燥转换点干基含水率(2.00~5.00 g/g)、热风温度(50.0~70.0 ℃)及微波功率密度(6.67~33.33 W/g)对香菇营养成分、干燥特性及品质的影响。通过单因素实验确定较优参数范围并采用Box-Behnken组合设计优化联合干燥工艺,分析干燥工艺对干燥时间及香菇典型品质(色差、收缩率及多糖保留率)的影响。结果表明,通过响应面优化试验获得最优工艺为转换点干基含水率4.20 g/g、热风温度60.60 ℃、微波功率密度30.00 W/g,此条件下的联合干燥时间为178.33 min(其中热风干燥170 min,微波干燥8.33 min),产品色差ΔE为11.21,收缩率为65.28%,多糖保留率为66.98%,综合评分为0.145。研究结果表明热风-微波联合工艺能够实现对香菇的快速干燥,并保证较好的干品品质。     

Conical spouted bed drying of Baker's yeast: Experimentation and multi-modeling

Baker's yeast drying experiments in a conical spouted bed are used to characterize the effects of operating conditions on drying behavior. A novel multiscale model, describing Baker's yeast drying in a conical spouted bed, is presented; it is based on an intrinsic drying model developed for a single pellet, combined with a gas–solid flow model developed for a conical spouted bed. The resulting phenomenological model, which has only one adjustable parameter, is in good agreement with the experimental results. The model is capable of adequately predicting the drying rate of Baker's yeast pellets during the entire drying period in a conical spouted bed: from the beginning, where the water removal rate is limited by the air saturation with vapor during its residence time in the bed; to the end, where the water removal rate is dictated by internal resistance within the yeast pellets.The quality of dried Baker's yeast was characterized by measuring the gassing power in bread dough. This parameter was monitored during the conical spouted bed drying experiments. It was found that yeast degradation is linked to intracellular water removal (type D, end of the drying below a moisture content of around 0.5 (d.b.)) and it is mostly the rate of this water removal that controls the final quality of the product. Intercellular water removal (type E, beginning of the drying) was found to have no significant influence on yeast degradation. In all the cases, degradation is amplified when solid temperature is higher than 40 °C.     

Physical properties of parboiled wheat and bulgur produced using spouted bed and microwave assisted spouted bed drying

The main objective of this study was to compare the spouted bed and microwave assisted spouted bed drying on affecting physical properties of parboiled wheat and bulgur. Drying was performed at different temperatures (50 °C, 70 °C, 90 °C) and microwave powers (288 W, 624 W). Bulk and apparent density, bulk and apparent porosity, sphericity, color, microstructure and pore size distribution of parboiled wheat were investigated after drying. Yield and water absorption capacity were determined in bulgur samples. The effect of air temperature on physical properties of product except color was not significant in spouted bed drying. More porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. Sphericity and bulk density were higher when high temperature was combined with high microwave power. In microwave assisted spouted bed drying, similar yield value but lower water absorption capacity of bulgur were observed as compared to spouted bed drying.     

不同干燥方式对颗粒状果蔬品质变化的影响

分别对真空微波干燥、冷冻干燥、热风干燥及热风与真空微波联合干燥等不同干燥方式对颗粒状果蔬质量变化的影响进行了讨论，以VC和叶绿素的保持、色泽的差异、收缩和复水性能等为质量参数，分别进行比较。真空微波干燥在以上各质量参数方面，虽比冻干产品有一定差距，但远优于常规热风干燥。采用常规热风与真空微波联合干燥方式也能较好地改善颗粒状果蔬的品质。     

DRYING METHODS AND QUALITY OF SHRIMP DRIED IN A JET-SPOUTED BED DRYER

The objective of this study was to experimentally investigate the effects of various parameters, i.e., size of shrimp, level and pattern of inlet drying air temperature, on the drying kinetics and various quality attributes of dried shrimp viz. shrinkage, rehydration ability, texture and color during drying in a jet‐spouted bed dryer. It was found that the use of a constant inlet air temperature of 100C yielded dried shrimp of the best quality in terms of low percentage of shrinkage, high percentage of rehydration, low maximum shear force and high value of redness compared to shrimp dried using other conditions. A simple mathematical model that enables prediction of the drying behavior of shrimp in a jet‐spouted bed dryer has also been developed.