用颗粒热传递模型计算旋转列管干燥机的传热系数

采用基于移动加热板的颗粒热传递模型计算大型旋转列管干燥机的传热系数。在料床完全混合的简化假设下 ,按物料在干燥机内的实际干燥过程分段计算各段的传热系数及整机总传热系数 ,其结果与干燥机的实际运行情况基本相符。     

垂直旋转圆盘内蒸汽与物料间的传热性能

以建筑用砂为实验材料,基于旋转圆盘干燥机搭建单个垂直旋转圆盘传热实验台,根据能量守恒定律研究垂直旋转圆盘转速、物料颗粒粒径、物料填充率对传热性能的影响.结果表明,转速对传热性能影响较大,几乎呈线性增长关系;物料颗粒粒径和物料填充率与平均传热系数分别呈近似线性下降和上升关系.圆盘表面气膜传热热阻约为颗粒传热热阻的26倍.     

旋转圆盘式和旋转管束式干燥设备的设计

推广使用具有节能环保特性的间接式干燥设备是目前干燥技术发展的一个重要趋势。着重就旋转圆盘和旋转列管式这两种间接加热干燥设备的结构特点及工作原理作了介绍，并根据颗粒热传递模型给出实际传热系数计算公式。同时对旋转圆盘和旋转列管式干燥机承压转子的危险部位及其校核内容进行了归纳。     

旋转圆盘干燥机在火电厂脱硫石膏处理中的应用

介绍了脱硫石膏的特性和旋转圆盘干燥机的工作原理,将旋转圆盘干燥机应用于火电厂脱硫石膏的处理工艺中,阐述了烘干工艺流程与主要技术参数。实践表明,旋转圆盘干燥机的烘干工艺具有高效、节能等独特优势。     

热传导式搅拌干燥机

热传导式搅拌干燥机依据搅拌器的结构有圆筒形搅拌干燥机,螺旋形搅拌干燥机、管形搅拌干燥机、圆盘搅拌干燥机、捏合式搅拌干燥机等。     

热传导式搅拌干燥机

热传导式搅拌干燥机依据搅拌器的结构有圆筒形搅拌干燥机,螺旋形搅拌干燥机、管形搅拌干燥机、圆盘搅拌干燥机、捏合式搅拌干燥机等。     

大型圆盘干燥机液压顶升的技术分析

介绍了圆盘干燥机的结构、工作原理,对圆盘干燥机升降技术分析,对设备升降可能出现的问题,采取了的预防措施。     

草甘膦节能干燥技术的研究与开发

分析计算了内加热对流化床干燥过程热效率的影响。实验测定了草甘膦流化床干燥机中内加热传热系数,设计开发了用于草甘膦干燥的内加热流化床干燥机,并与普通流化床干燥机和气流干燥机进行了分析对比。     

污泥间接干燥过程的实验研究

污泥间接干燥是以热传导为传热方式的干燥过程。采用楔形桨叶式干燥机进行污泥干燥实验,研究了污泥的间接干燥过程,测得了污泥在干燥机不同位置的温度及其相应的含水率,验证了污泥的间接干燥过程遵循预热阶段、恒速干燥阶段和降速干燥阶段的一般规律,获得了不同转速下污泥干燥过程的平均传热系数,且平均传热系数随着搅拌转速的提高而增大。     

装有双层蛇管搅拌釜的传热

以水为传热介质，采用组合桨，测定了装有双层蛇管的搅拌釜的传热系数。结果表明，在三层圆盘涡轮搅拌下，外层蛇管外壁侧和釜内壁侧的传热系数分别比内层蛇管的下降了１０％和２８％，而用圆盘涡轮与折叶桨组合桨搅拌时，要分别高出３３％和５％，总传热效率提高了２０％以上；另外，釜内壁侧的传热系数受蛇管层数的影响较小。     

Heat transfer in an indirect-heat agitated dryerWärmeübertragung in indirekt beheizten Trommeltrocknern

The heat transfer coefficients between the heating plane and the granular material under agitation in a small indirect-heat agitated dryer with both moving and stationary heating planes were measured in order to obtain data for its design and to analyse the heat transfer mechanism. Based on the ‘particle heat transfer model’ suggested by Schlünder and partly revised by Mollekopf and Martin, heat transfer models for both types of heating planes were proposed to correlate the observed heat transfer coefficients. Comparison between the experimental and calculated heat transfer coefficients showed no serious deviation in either case. Using these models, it is possible to estimate the heat transfer coefficient between the heating plane and the granular material in this type of dryer.     

循环流化床的沸腾传热

A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39 mm ID and 2.0 m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.     

Experimental Study of the Heat and Mass Transfer During Drying in a Fluidized Bed Dryer

Drying curves obtained in a pilot-scale fluidized bed dryer using biological source solids (sawdust, soya and fish meal) were used to estimate the parameters involved in heat and mass transfer phenomenas: heat transfer coefficient and moisture diffusivity coefficient. Parameters involved in mass transfer were estimated from drying models based on diffusional mechanisms and others that in addition consider internal and external resistance to the mass transfer. The estimate ef ective diffusivity coefficient was between 2x10-11 to lx10 (m2/s) for the considered products. Heat transfer coefficient was estimated from drying data points in the constant drying rate period when the external resistance to the mass transfer controls the process.     

Experimental Study of the Heat and Mass Transfer During Drying in a Fluidized Bed Dryer

ABSTRACT

Drying curves obtained in a pilot-scale fluidized bed dryer using biological source solids (sawdust, soya and fish meal) were used to estimate the parameters involved in heat and mass transfer phenomenas: heat transfer coefficient and moisture diffusivity coefficient. Parameters involved in mass transfer were estimated from drying models based on diffusional mechanisms and others that in addition consider internal and external resistance to the mass transfer. The estimate ef ective diffusivity coefficient was between 2x10-11 to lx10 (m2/s) for the considered products. Heat transfer coefficient was estimated from drying data points in the constant drying rate period when the external resistance to the mass transfer controls the process.     

Mass and Heat Transfer in a Continuous Plate Dryer

Abstract

A mathematical model for the mass-heat transfer in a continuous plate dryer has been developed. Along with a new mass transfer model, the formulas for several important parameters, such as height, volume of each granular heap and retention time, are provided. According to the penetration model of particle heat transfer, the average drying rate ([mdot]) is predicted together with the mean bulk temperature (T _out) and moisture content (X _out) by a straightforward stepwise calculation procedure. The only empirical parameter N _mix can be predicted by the method, provided that experimental data with various initial moisture contents (X _in) are given. According to the model, the optimization of a plate dryer should aim at the maximizing of the effective covering ratio (μ) and the total area-averaged heat transfer coefficient (α). The model and equations were applied in an experimental plant. In the result, the theoretical predictions are shown to be in satisfactory agreement with experimental data.     

Effects of Drying Parameters on Heat Transfer during Drying of Fermented Ground Cassava in a Rotary Dryer

The effects of drying parameters on heat transfer during drying of fermented ground cassava in a rotary dryer were studied. The fermented ground cassava was dried in a bench-scale rotary dryer at different inlet air temperatures, inlet air velocities, relative humidities, feed rates, drum drive speeds, and feed drive speeds. It is shown that inlet air temperature, inlet air velocity, and feed rate have significant effects on the specific heat transfer coefficient and heat load in the material. Models that predict the specific heat transfer coefficient as a function of inlet air temperature and inlet air velocity and the heat load as a function of inlet air temperature, inlet air velocity, and feed rate are also presented. Predictions of the models are compared with experimental data and good agreement is obtained.     

Heat and Mass Transfer in an Agitated Contact-Convective Heated Dryer

For the investigation of the drying process of a pharmaceutical fermentation waste and for determining specific heat and mass transfer coefficients an agitated contact-convective heated dryer was constructed. This dryer is also suitable for drying of other granular solids with high moisture content. Hence we investigated the drying of a by-product from bio-ethanol production, as well. The pilot-plant agitated dryer makes possible continuous measurement and data-acquisition. Data-acquisition of heated wall temperature, inlet and outlet air temperatures and humidity, mass reduction of the material makes possible the determination of transfer coefficients by the heat and mass balance of the dryer. The measured heat and mass transfer coefficients serve as proper input parameters for the simulation calculations.     

气体冲击液相中加热面的气化热阱模型

<正>很久以来,人们就认识到在液相中注入气泡可以产生强烈扰动,大在强化了对流传热和沸腾传热.不久前,C.F.Ma和Bergles侧进一步发现用异种气体快速冲击浸没在R-ll3中的微小加热壁面,其传热不但大为强化;而且可出现壁面温度低于液体冷却介质温度的“负温差传热”的奇异现象.此外,沈自求等最近亦发现,在蒸发过程中引入少量载气,可在气液界面上产生快速质量传递,使沸腾传热得到明显强化.此类现象的深入探讨对强化电子元件、蒸发器、原子能反应堆的传热均具有重要意义.     

The Gas-to-Particle Heat Transfer and Hydrodynamics in Spouted Bed Drying of Sawdust

This article presents experimental results for spouted bed drying of sawdust, carried out in a full-scale as well as in a laboratory-scale dryer using air as well as steam as drying media. The aim is to present design parameters for a spouted-bed sawdust dryer that can be used by the industry in designing full-scale dryers. A hydrodynamically stable spouted jet spouted bed was obtained. The heat transfer characteristics of the bed were represented in terms of a volumetric heat transfer coefficient (VHC). When sawdust is dried in a spouted bed, the mean VHC is increasing up to fiber saturation level (20-25% wb) from 40 to 110 W/m³ K. The VHC decreases with the residence time and with an increased static bed height. Gas temperature profiles are also presented for the bottom part of the drying chamber.