Mathematical Modelling and Design of Helical Coil Heat Exchanger for Production of Hot Air for Fluidized Bed Dryer

In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil heat exchanger (HCHE) has been proven to be effective in improving heat transfer due to its large surface area. In this study, HCHE was designed to provide hot air needed for fluidized bed drying processes. The HCHE design model was fabricated and evaluated to study the efficiency of the hot air output for a laboratory fluidized bed dryer. The mathematical model for estimation of the final (output) temperature of air, Taf, passing through the HCHE was developed and validated experimentally. The drying of bitter kola particulates was carried out with a drying temperature of 50C 3C and a bed height-to-bed diameter ratio (H/D) of 1.5. The time taken to dry bitter kola particulates to 0.4% moisture content was 1 hour 45 minutes. Hence, HCHE is recommended for use in the production of hot for laboratory-scale fluidized bed dryers.

A Comprehensive Review of Design and Technological Advancements across Various Types of Solar Dryers

This analysis investigates the widespread use of solar drying methods and designs in developing countries,particularly for agricultural products like fruits,vegetables,and bee pollen.Traditional techniques like hot air oven drying and open sun drying have drawbacks,including nutrient loss and exposure to harmful particles.Solar and thermal drying are viewed as sustainable solutions because they rely on renewable resources.The article highlights the advantages of solar drying,including waste reduction,increased productivity,and improved pricing.It is also cost-effective and energy-efficient.The review study provides an overview of different solar drying systems and technologies used in poor nations,aiming to identify the most effective and efficient designs.The focus is on comparing current models of solar dryers for optimal performance.The review underscores the importance of solar drying as a long-term,eco-friendly approach to drying food in developing countries.This review aims to evaluate how using solar-powered drying techniques can enhance food preservation,minimize waste,and enhance the quality and marketability of agricultural goods.The paper will specifically focus on examining the efficacy of these methods for drying bee pollen and pinpointing where enhancements can be made in their advancement.

Experimental Study and Thermal Modelling of Cocoa Shell Convective Drying in an Indirect Solar Dryer

The concern of the present work is the convective drying of empty cocoa shells in an indirect solar dryer. Some drying experiments, using one sample, were carried out. During the experiments, the sample is introduced in the drying chamber. Then at steady time intervals, the sample is withdrawn from the drying chamber, for a rapid weighing. After each weighing, the sample is reintroduced in the dryer. At each time interval, the ambient temperature of the drying chamber and its relative humidity γ are measured by a thermo-hygrometer. From the experimental data, a theoretical determination of the moisture evaporated from the product was performed and a good agreement was found between the theoretical and experimental values, confirmed by the value of the RMSE. Those calculations used the constants in the Nusselt number found in literature. Then those constants were evaluated again, to get new values more suitable with the experimental data. The dimensionless numbers of Nusselt, Grashof and Prandtl were calculated. That allowed the calculation of the average value of the Nusselt number. The average convective heat transfer coefficient was determined.

Heat and Mass Transfer for a Nanofluid Flow in Fluidized Bed Dryer in Presence of Induced Magnetic Field

This research entails the study of heat and mass transfer of nanofluid flow in a fluidized bed dryer used in tea drying processes in presence of induced magnetic field. A mathematical model describing the fluid flow in a Fluidized bed dryer was developed using the nonlinear partial differential equations. Due to their non-linearity, the equations were solved numerically by use of the finite difference method. The effects of physical flow parameters on velocity, temperature, concentration and magnetic induction profiles were studied and results were presented graphically. From the mathematical analysis, it was deduced that addition of silver nanoparticles into the fluid flow enhanced velocity and temperature profiles. This led to improved heat transfer in the fluidized bed dryer, hence amplifying the tea drying process. Furthermore, it was noted that induced magnetic field tends to decrease the fluid velocity, which results in uniform distribution of heat leading to efficient heat transfer between the tea particles and the fluid, thus improving the drying process. The research findings provide information to industries on ways to optimize thermal performance of fluidized bed dryers.

Design and Development of a Parabolic Trough Solar Air Heater for a Greenhouse Dryer

Design and Development of a Parabolic Trough Solar Air Heater (PTSAH) for a Greenhouse Dryer (GD) was done to improve the dryer’s performance. The materials used for the fabrication of the PTSAH included galvanized sheets covered with aluminium foil, an absorber tube made of GI pipe painted matt black to increase heat absorbance at the focal line, mild steel square tubes, shutter plywood, and an axial fan to push air through the absorber tube. Key geometrical parameters used for the design of the PTSAH were a rim angle of 98 degrees, focal length of 0.2608 m, height of 0.3451 m, length of 2 m, and an aperture width of 1.2 m. The PTSAH’s total aperture surface area was 2.4 m2, while its absorber tube surface area was 0.1587 m2. The PTSAH was experimentally tested to establish its thermal performance. It was found that the ambient air recorded an average value of 31.1˚C and that the air heater could increase the air temperature by 45.6˚C above ambient with a thermal efficiency of 5.3%. It can, therefore, be concluded that the PTSAH can significantly improve the performance of a GD by supplying the GD with air at a higher temperature than ambient.

Experimental Study of a Modified Icaro Solar Dryer: The Case of Coffee Drying

Food losses in the developing country are thought to be 50% of the fruits and vegetables grown and 25% of harvested food grain. Food preservation can reduce wastage of a harvest surplus, allow storage for food shortages, and in some cases facilitate export to high-value markets. Drying is one of the oldest methods of food preservation. Drying makes produce lighter, smaller, and less likely to spoil and helps to minimize the moisture content in coffee beans as high moisture content during storage is certain to ruin the taste and appearance of coffee. This work presents the results of an experimental study of forced convection drying of coffee cherries in a modified Icaro solar dryer. The study aims to validate the numerical models developed for further research. The experimental tests envisaged also aim to determine the mass loss curves of the product by fixing or calculating its initial mass (1 kg), its initial water content (70%), the ambient temperature, the drying airflow (0.02 m3.s-1 to 0.09 m3.s-1) and the exchange coefficients. The influence of these aerothermal parameters on the drying time of a most commercialized coffee variety (Robusta) was studied. Finally, the results revealed an increase in the efficiency of the heat transfer air and a reduction in the water content of the coffee cherry from 70% to 9.87%, after 30.2 hours.

Experimentation of a Forced Convection Solar Dryer for Drying Sweet Potatoes at the Higher Institute of Technology of Mamou-Guinea

This study was carried out at the Mamou Higher Institute of Technology during the period from March 10 to April 15, 2022, with the aim of designing and testing a solar dryer with forced convection by drying potatoes. The dryer was designed using local materials. Its main geometric parameters are: 1) height of the drying chamber (90 cm), 2) length of the drying chamber (50 cm), 3) width of the drying chamber (43 cm), 4) surface of the racks (0.1806 m2), 5) surface of the heat accumulator (0.2537 m2). The experiment focused on the vacuum test of the dryer for two days and that of the drying of the sweet potato for three days from 8:30 a.m. to 5:30 p.m. The average vacuum test temperature values of the three environments are respectively accumulator (43°C), dryer chamber (41°C) and ambient environment (34°C). Four kilograms (4 kg) of boiled sweet potato were dried. The average temperatures in the accumulator and in the drying chamber during the three days of drying are respectively 33°C and 39°C. The final mass of the dried product is 1.2 kg, with a quantity of water extracted of 2 liters or 63% of the initial mass of the product. The average drying rate is 0.074 kg/h. The drying kinetics showed a decreasing rate in the absence of the heating period and the constant rate period.

Optimizing Solar Drying: A Critical Review of Shapes, Orientation, and Future Prospects for Hybrid Solar Dryers

This comprehensive review focuses on the performance of solar dryers, with a specific emphasis on their structural shape and orientation. Researchers have extensively examined these design parameters, often employing Computational Fluid Dynamics (CFD) to assess thermal attributes and predict temperature distribution, airflow patterns, and temperature profiles within the structures. Geographical location significantly influences solar dryer shape preferences, with the parabolic shape finding favor in tropical regions for its superior solar radiation capture and storm resistance, while even-span and Quonset shapes are popular elsewhere. Solar dryer orientation is another crucial factor, with east-west alignment consistently proving optimal due to its ability to maximize year-round solar radiation absorption and, consequently, enhance drying efficiency. Economic considerations, however, fall beyond the scope of this review, which predominantly focuses on thermal aspects. This investigation reveals diverse global preferences for solar dryer shapes and orientation, highlighting the necessity of considering geographical factors in design choices. While CFD and shape/orientation dynamics have provided valuable insights, there remains room for future research to expand into transient state simulations under various conditions, contributing to a more comprehensive understanding of solar dryer performance. Such insights promise to promote sustainable and efficient drying processes, benefitting agricultural and drying applications across the globe.

基于多因素分析的烘丝机智能调控研究

烘丝过程中影响出口烟丝水分和温度的干扰因素较多,为了保障出口烟丝水分与温度的稳定性,首先基于烘丝过程的历史数据,采用相关性分析方法对影响因子进行筛选。其次,选取出口烟丝水分和出口烟丝温度为目标值,通过对各机器学习模型的对比分析选取了能够快速建模与预测的极限学习机(extreme learning machine,ELM)作为建模方法,以通过模型求解运算,得出预测值。最后,采用模拟退火(simulated annealing,SA)算法,实时优化热风风速和排潮风门开度的设定值,实现对出口烟丝水分和温度的预测和控制。实验结果表明,极限学习机模型的预测效果良好,预测当前出口水分的均方根误差为0.015,出口温度的均方根误差为0.638,误差较小,保障了烘丝机智能调控方法的调控精度。

基于TRIZ与DFSS的污泥烘干机专利规避创新设计

为解决传统专利规避设计缺乏合理的挖掘与解决问题的过程,其设计方案可能存在潜在失效模式的问题。结合TRIZ与六西格玛设计提出一种新的专利规避创新设计方法,并将其应用到污泥烘干机的专利规避创新设计当中。挖掘并分析目标专利,识别需求,进而确定规避方向,进行改进创新设计并做优化。成功对现有污泥烘干机专利进行了规避创新设计,使创新之后的污泥烘干机具有烘干效率高、节能环保、有效防粘壁、实现自动上料的优点。验证了所提出方法的可行性,为企业产品的专利规避设计提供了参考。

新型真空耙式干燥机优化设计与蒸发性能研究

针对现有耙式干燥机运行中存在的蒸汽消耗大、干燥效率不高、传热不均匀等技术难题,以及筒内残余滤渣层造成较大的物料损失,难以满足安全、环保和GMP(良好生产规范)要求等技术难点,通过查阅文献并进行大量的实验研究,设计了一种高效、节能耙式干燥机,自主提出一种轻量化的内、外筒与浆叶复合加热搅拌轴结构。该结构中心转轴、连接轴和搅拌桨叶均为空心设计,桨叶刮擦部距离筒壁间隙3~5 mm,达到了所需搅拌动力显著降低、换热面积大、传热效率高的效果,实现了不留残余物料、降低生产成本、保证人和物料的完全隔离的目的,可满足制药行业的GMP要求。实际试验研究结果表明,干化减量比例达19.9%,蒸汽单耗32.8%,能耗明显减少,说明该方法与设备具有较高的推广应用价值。

Development and Experiment of Multi- functional Wood Dehumidification Dryer

A multi functional wood dehumidification dryer has been developed recently. The dryer can carry out air dehumidification by using only one refrigeration system, in which heat supplying and moisture air are exhausted by changing the position of several air dampers. In this paper, the work principles and characteristics of the dehumidification dryer are introduced, and the testing results about the thermal engineering performance of the dehumidification dryer, as well as the experiment results of drying several species of lumbers are expounded.

基于物联网的热泵式低温循环粮食烘干机监控系统研究

针对热泵式低温循环粮食烘干机监控手段落后、信息化程度低等问题,设计了基于物联网的热泵式低温循环烘干机监控系统。系统采用感知层、传输层和应用层相结合的体系架构,以可编程控制器(Programmable logic controller,PLC)和HMI触摸屏为核心,设计开发控制系统,实现对烘干机和热泵的实时监测、图形化显示、安全保护和自动化控制;采用Linux的CentOS系统开发服务端系统框架,通过EG8000mini模块将采集的数据接入AP基站并存储至数据库,使用户可以通过计算机端或手机APP对热泵式低温循环粮食烘干机进行远程实时监控。试验验证结果显示,系统通信成功率高于98%,对环境温度、热风温度、热风相对湿度及热风风速实时检测平均绝对误差分别为0.3℃、0.26℃、1.2%和0.47 m/s,可满足热泵式低温循环烘干机远程监控需求。

带式烘干机风速场均匀性试验研究

物料含水率均匀性是物料品质的重要指标,与烘干机内部气流均匀性相关。烘干机结构与工艺参数对烘干机内部流场均匀性产生较大影响。使用正交试验的方法研究导流板角度(30°、40°、50°)、侧风道均流板个数(1、2、3)与循环风机频率(20 Hz、30 Hz、40 Hz)对烘干机内气流分布的影响,找到最优的因素水平,使烘干机内部风速场最均匀。研究结果表明:风机频率对上料层的风速场影响最显著;导流板角度对上料层风速场影响最不显著。导流板角度对下料层风速场影响最显著;风机频率对下料层风速场影响最不显著。当因素水平组合为导流板角度30°,均流板3个,风机频率20 Hz时,烘干机内风速场最均匀。

基于CFD茶叶烘干机的优化设计与试验

针对目前6CH型自动链板式茶叶烘干机存在结构设计欠合理、温度分布不均匀性等问题,对6CH型自动链板式茶叶烘干机进行优化设计与试验。将导流板的布置进行优化设计,对优化后的茶叶烘干机采用计算流体力学软件CFD建立干燥机部件的稳态温度场仿真模型,通过截面温度、速度云图,分析得到3组工况下(进风速度20 m·s^(-1)温度130℃、进风速度25 m·s^(-1)温度140℃、进风速度30 m·s^(-1)温度150℃),干燥室内部均能满足所需高温环境,并且能满足物料快速烘干再掉落至下一层的要求。采用三因素三水平正交试验,确定实际工况下的最优参数组合,试验结果表明,当进风温度为144.81℃、鼓风机风速为20.62 m·s^(-1)、输送速度为1.78 m·s^(-1),基于此组合下的降水幅度为40.75%,碎茶率为2.07%,均满足且超过农艺要求,该研究为茶叶烘干与烘干机关键参数优化提供参考。

5H-2谷物烘干机干燥箱多孔角状盒的设计与试验

为改善5H-2谷物烘干机的干燥性能,将原有角状盒改造为多孔角状盒。通过Fluent对多孔角状盒的干燥段气流场进行仿真分析,对比空载条件下干燥箱内部温度场变化情况,结果表明,装有多孔角状盒的干燥箱内部温度场较原有角状盒的分布更趋均匀。选择早稻‘中早35’稻谷,在5H-2谷物烘干机上安装多孔角状盒开展烘干试验,设置热风干燥温度为65℃,风速为8 m/s,干燥缓苏比为1∶2,结果装有多孔角状盒的烘干机干燥速率为0.798%/h~1.002%/h,烘干后爆腰增率为7.4%~10.2%,相比原有角状盒谷物烘干机,其干燥速率提高了12.1%~21.2%,爆腰增率降低了1.9%~5.1%。

船舶洗衣烘衣间通风系统设计

船舶洗衣烘衣间内的烘衣机运行过程中产生的高温湿气体会给室内环境带来不利影响,在设计该舱室的通风系统时需将这些高温湿气体排至室外。基于此,对常见的烘衣机类型及其工作原理进行归类和介绍,结合设计规范总结船舶洗衣烘衣间通风系统的常用形式和配置,并从工程实际出发提出通用性设计方案,例如利用烘衣机余压直接排风、单独为烘衣机设置机械排风和将烘衣机排风与洗衣烘衣间排风混合等。在具体设计船舶洗衣烘衣间通风系统时,可有针对性地借鉴相应解决方案。

短管直径对短管蜂窝夹套传热性能的影响

基于某工程中1台干燥机的短管蜂窝夹套结构形式,通过将短管尺寸由Ф90 mm×5 mm逐渐增大到Ф135 mm×7.5 mm,建立了模型1~模型6共6种夹套流场计算有限元模型,模拟分析了各模型速度场和温度场分布特性,计算并对比了各模型在不同体积流量下的总传热系数。模拟数据表明,随着短管尺寸的增大,夹套流体域内最大流速呈持续递减趋势。随着短管尺寸的增大,夹套流体域内温度场均匀性先升后降,模型5温度场分布均匀性最佳,总传热系数最大。随着体积流量的增加,夹套总传热系数持续增大。随着短管直径的增大,夹套总传热系数先升后降,模型5总传热系数最大。综合分析表明,在一定范围内增大短管的直径,能够强化夹套传热效果。

连续重整装置再生循环气干燥系统腐蚀分析与对策

对于催化剂再生采用干冷循环的连续重整技术,再生循环气干燥是连续重整装置中不可或缺的系统,近年来多次发生腐蚀泄漏问题,严重影响装置的长周期运行。针对4个连续重整装置再生循环气干燥系统发生的腐蚀案例,分析了系统内冷却器、分离器以及相连管道的腐蚀原因。结果发现腐蚀原因主要是酸性气露点腐蚀和循环水腐蚀。针对腐蚀现状,提出了一系列延长操作周期的控制措施:工艺设计上增加换热器壳程进出口安装倾斜角度,增加过滤器;选材上分离器及相连管道增加玻璃钢或PTFE(聚四氟乙烯)衬里,水冷器碳钢管束增加涂层防腐;操作上控制循环水水质,加强工艺参数和腐蚀情况监测。

碳化钨涂层盘管的制备及寿命预测

针对冶金行业蒸汽干燥机内部盘管冲蚀磨损问题,使用超音速喷涂工艺制备碳化钨涂层盘管提高盘管的使用寿命。通过显微金相检测与拉伸试验获取盘管表面状况与结合强度。基于FLUENT建立了计入壁面硬度实验值的盘管冲蚀模型,通过仿真云图与现场磨损图片进行比对,验证了数值仿真模型的合理性与真实性。将模型与冲蚀率做统一量纲化处理后,对盘管冲蚀磨损寿命进行预测。结果表明,超音速喷涂备至涂层盘管金相观测孔隙率小于0.1%,厚度大于90 um,表面硬度大于1000 HV,结合强度大于70 MPa,喷涂工艺可靠性较好;仿真结果表明,盘管冲蚀率在35°入射角附近达到最大,最大值为1.92×10^(-7) kg/(m^(2)·s);冲蚀率预测盘管极限工况使用寿命达36718750 s,较喷涂前提高约145%~167%;预测正常工况寿命41592920 s,较喷涂前提高约154%~177%。