多层水平气流带式干燥机的数学模型

根据干燥传质传热学原理和干燥动力学特性，建立了水平气流带式干燥机干燥过程的数学模型。该模型可以预测干燥机合理的通风道高度、带翻转最佳时间和热风风速等。为优化多层带式干燥机的结构或设计新的水平气流带式干燥机提供了理论依据。     

穿流气流带式干燥机设计计算

穿流气流带式干燥机操作灵活方便,便于控制,该机由多个独立干燥单元组成,每个干燥单元包括循环风机、加热装置、引风机管道及网带系统的一部分组成。热风的流量、温度以及流向都可以按需要选择。通过控制阀门,可将各干燥单元控制在物料所适宜的温度下进行恒温干燥或调温干燥,还可以控制各干燥单元热风的温度、湿度以及调节接触面积,增大传热效率,提高生产能力。     

真空带式干燥机的应用及研究进展

真空带式干燥机(VBD)由干燥室、真空系统、布料机构、履带输送装置、切料机构、CIP清洗系统、PLC控制系统、加热和冷却系统以及卸料系统组成。干燥室内真空度为1 000—3 000 Pa,物料温度为30—60℃,适用于热敏及氧敏性物料的干燥,其传热方式为传导-辐射联合传热。目前有关真空带式干燥机干燥特性及传热传质机理的研究报导较少,难以指导工业设备的设计与生产,故而真空带式干燥机的设计主要是依靠经验,这使得其节能降耗的优势不能充分体现出来。真空带式干燥属于薄层干燥,文中综述了真空薄层干燥方面的一些研究文献,为真空带式干燥机的理论研究奠定了基础,以期研究者们进一步对真空带式干燥机的干燥特性及传热传质理论进行研究。     

穿流气流带式干燥机设计与应用

一、概述 穿流气流带式干燥机主要由头部、物料成形机构、若干干燥单元、出料装置、网带运行机构等组成。它采用强制通风干燥法。由于热风和湿物料的接触面积大,既有对流传热,又有辐射传热,干燥热强度大。同时,因湿物料内部水汽排出的途径较短,因此具有较大的干燥速度。 本机能够连续操作,湿物料直接或经过物料成形机构分布到多孔网带运行机构上,     

强化气流干燥机的设计

介绍了强化气流干燥机的设计方法.强化气流干燥机是在直管气流干燥器的基础上发展起来的,用于解决各种农药滤饼的干燥问题,对高黏度膏状物料的干燥有很好的效果.     

物料在盘式连续干燥机干燥盘上运动规律的研究

通过物料在圆盘上运动的速度三角形推导出物料在大干燥盘和小干燥盘上运动轨迹的极坐标方程和速度方程。物料在干燥盘上的运动轨迹为指数螺旋线。这种运动轨迹使物料在干燥盘上经过的距离比单纯的径向距离要多好几倍 ,增加了物料在干燥盘上加热的时间 ,提高了干燥效果。这对于认识盘式连续干燥机的干燥机理 ,改进干燥机的结构 ,提高干燥效果都具有非常重要的意义。     

粉碎气流干燥机的设计

历来膏糊状物料的干燥是个难题,适用于此类物料的干燥机较少。强化气流干燥机使许多膏糊状物料得以直接干燥,大大提高了热效率。现在,这一机型已普遍用于染料、颜料等行业。本文介绍了强化气流干燥机的工作原理、结构、设计方法。     

白萝卜条干燥工艺参数的优化研究

采用新型的旋转式干燥机，通过对白萝卜条单因数试验及三因数二水平的二次回归正交试验，分析了温度、通风量、物料厚度对干燥时间的影响；经过优化，确定了不同物料厚度下的最佳干燥时间。     

磷酸二氢钠转化为酸式焦磷酸钠的干燥试验研究

针对磷酸二氢钠转化为酸式焦磷酸钠的特点，提出使用转鼓干燥机与桨叶干燥机结合的方法对磷酸二氢钠进行干燥脱水，并进行了试验验证。在试验条件下，干燥过程中物料没有出现团聚和粘结现象，结片及干燥效果良好。干燥后，物料为粉末状且含水量低于0.1%。     

搅拌式旋转气流干燥机及其应用

叙述了搅拌式旋转气流干燥机的基本结构、工作原理,分析了物料的运动和干燥过程,并介绍了这种干燥机的应用     

Analysis of Energy Consumption in Drying Process of Non-Hygroscopic Porous Packed Bed Using a Combined Multi-Feed Microwave-Convective Air and Continuous Belt System (CMCB)

In this study, the analysis of energy consumption during the drying of non-hygroscopic porous packed bed by combined multi-feed microwave-convective air and continuous belt system (CMCB) was investigated experimentally. By using a combined multi-feed microwave-convective air and continuous belt system drier, the microwave power was generated by means of 12 compressed air-cooled magnetrons of 800 W each that give a maximum of 9.6 kW. The power setting could be adjusted individually in 800 W steps. Hot air with the maximum working temperature of 240°C was generated using 24 units of electric heater where the total power capacity is 10.8 kW. Most importantly, this work focused on the investigation of drying phenomena under industrialized microwave processing. In this analysis, the effects of the drying time, hot air temperature, porous structure (F-Bed and C-Bed), and location of magnetrons on overall drying kinetics and energy consumption were evaluated in detail. The results showed that the overall drying and energy consumption depend upon the porous structure, hot air temperature, and location of magnetrons. Furthermore, using the continuous microwave application technique had several advantages over the conventional method, such as shorter processing times, volumetric dissipation of energy throughout a product, and less energy consumption. The results presented here provided fundamental understanding for the drying process using a combined multi-feed microwave-convective air and continuous belt system in industrial size.     

CRAPE DRYING : FROM SAMPLE BEHAVIOUR TO THE DRIER PROJECT

A drier project necessitates the efficient formulation of the behaviour of product samples. When the temperature gap is great, the drying rate must make explicit the influence of the thnc air parameters : temperature, moisture, velocity. The case of the grape demonsnates that the adimensional expression formulated by Van Meel and Keey. must be completed in order to be adjusted to experiments.

The hot air drier model composed of the equations of conservation and thin layer drying rate can sometimes be simplified into a form of analytic integral equation around the drying rate. W e drying can be considered generally as adiabatic.

Two examples of grape driers are presented and show the value of simplified tools for the project. In a tunnel drier with a high air temperature one can speak of the celerity of a drying front which progress along the trolleys. In a short drier connected to an agricultural solar collector, the integration of the drying rate takes into account the variation of the meteorological data.     

CRAPE DRYING : FROM SAMPLE BEHAVIOUR TO THE DRIER PROJECT

ABSTRACT

A drier project necessitates the efficient formulation of the behaviour of product samples. When the temperature gap is great, the drying rate must make explicit the influence of the thnc air parameters : temperature, moisture, velocity. The case of the grape demonsnates that the adimensional expression formulated by Van Meel and Keey. must be completed in order to be adjusted to experiments.

The hot air drier model composed of the equations of conservation and thin layer drying rate can sometimes be simplified into a form of analytic integral equation around the drying rate. W e drying can be considered generally as adiabatic.

Two examples of grape driers are presented and show the value of simplified tools for the project. In a tunnel drier with a high air temperature one can speak of the celerity of a drying front which progress along the trolleys. In a short drier connected to an agricultural solar collector, the integration of the drying rate takes into account the variation of the meteorological data.     

The Influences of Drying Process on Crude Protein Content of Naked Oat Cut Herbage (Avena nuda L.)

The effects of thin-layer drying naked oat cut herbage process (hot air temperature, air velocity, and drying time) on crude protein content were investigated. It was observed that an increase in drying temperature could lead to a significant drop in the crude protein content of naked oat cut herbage. The crude protein content also decreased with an increase in drying time and air velocity, and air velocity had a minimal impact during processing. A thin-layer drying mathematical model of crude protein content for naked oat cut herbage was established. The optimal drying parameters were determined as hot air temperature of 88.6–94.2 ^° C, air velocity of 0.28–0.32 m/s, and drying time of 16.4–20.6 min.     

HOT AIR AND MICROWAVE DRYING OF ONIONS: A COMPARATIVE STUDY

This comparative study of conventional (hot air) drying and microwave drying of the onion was carried out on a hot air pilot plant drier for conventional drying where all characteristics (temperature, humidity, and velocity) could be adjusted and controlled. A data logger connected to a computer captured all data. And for microwave drying, a drying tunnel Fitted with a forward/backward movement was used. Mass loss and product surface temperature were monitored for both processing. Factors controlled where: frequency of movement, microwave power, air extraction rate. Other elements included shape (slices/pieces) and variety of product

Drying duration and maximum drying rate constituted comparative criterion for the processes. Quality was measured by the reducing sugars and polyfructans content. Analysis of variance for the microwave drying process suggests that the effective factors were microwave power followed by onion variety and shape respectively. For quality criterion by far the most effective was variety, followed by the interaction of shape and the forward-backward movement of the conveyor. For conventional drying the most effective factor was air temperature for drying duration, and variety for maximum drying rate.     

HOT AIR AND MICROWAVE DRYING OF ONIONS: A COMPARATIVE STUDY

ABSTRACT

This comparative study of conventional (hot air) drying and microwave drying of the onion was carried out on a hot air pilot plant drier for conventional drying where all characteristics (temperature, humidity, and velocity) could be adjusted and controlled. A data logger connected to a computer captured all data. And for microwave drying, a drying tunnel Fitted with a forward/backward movement was used. Mass loss and product surface temperature were monitored for both processing. Factors controlled where: frequency of movement, microwave power, air extraction rate. Other elements included shape (slices/pieces) and variety of product

Drying duration and maximum drying rate constituted comparative criterion for the processes. Quality was measured by the reducing sugars and polyfructans content. Analysis of variance for the microwave drying process suggests that the effective factors were microwave power followed by onion variety and shape respectively. For quality criterion by far the most effective was variety, followed by the interaction of shape and the forward-backward movement of the conveyor. For conventional drying the most effective factor was air temperature for drying duration, and variety for maximum drying rate.     

Microwave-Assisted Spouted Bed Drying of Lettuce Cubes

Microwave-assisted spouted bed (MSBD) drying of lettuce cubes was investigated experimentally. Response surface methodology was used to optimize the process with spouting air temperature, microwave power level, and superficial air velocity. The dried product obtained was compared with that obtained using other drying technologies such as hot air drying, air spouted bed drying, vacuum microwave drying, and vacuum freeze drying. The comparison is based on the rehydration ratio, chlorophyll content of the product, color, and the drying time required.     

Drying and quality characteristics of tilapia fish fillets dried with hot air-microwave heating

The aim of this work was to study the effect of hot air-microwave heating on the drying and quality characteristics of fresh tilapia fish fillets. Experimental drying curves were obtained at three microwave powers (200, 400 and 600 W) after hot air drying at two air temperatures (40 and 50 °C) and a constant air velocity of 1.5 m/s. Some quality indicators such as shrinkage, rehydration and recovery properties were investigated. Results showed that an increase in microwave power resulted in a decrease in final moisture content when drying for the same period of time. The higher the hot air temperature, the higher the dehydration rate was. The shrinkage ratio and rehydration ratio increased as the microwave power and air temperature increased. However, the recovery ratio decreased as the microwave power and air temperature increased. Lower hot air temperature and microwave power are beneficial to keep the quality of tilapia fillets.     

Drying of Foamed Biological Materials: Opportunities and Challenges

An overview is provided on hot air drying of foamed materials in a thin layer (foam-mat drying), foam-spray drying, microwave-assisted drying of liquid foams, as well as microwave drying of frozen foams with and without dielectric solid inserts, used as complementary heat sources. In particular, the mechanisms of heat and moisture transport during the drying of foams are identified. The effects of foam characteristics (e.g., foam density and stability) and drying conditions (temperature, air velocity) on drying kinetics and product quality are examined, and the differences between the drying of non-foamed and foamed materials are discussed.