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 Then at steady time intervals, the sample is withdrawn from the drying chamber, for a rapid weighing.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.

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.

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。

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%。

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。

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。

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%。

蒸汽管回转干燥机出料箱故障研究分析

某厂PTA蒸汽管回转干燥机出料箱前后壁在运行过程中出现了规律性和间歇性的鼓包现象,导致出料密封内外两侧填料函间隙不均匀,密封密封效果不佳,出现漏料情况。经初步分析,认为是出料箱受到了的间歇性超压操作,过大的压力将出料箱挤压变形,出现鼓包现象,过量的弹性变形改变了填料函与轴套密封间隙的均匀性,填料出现挤压磨损,密封性变差。本文通过有限元数值方法对出料箱进行计算分析,发现出料箱在运行过程中若出现超压运行,就会导致出料箱前后壁位置出现较大的弹性变形。事后对现场操作流程进行了详细的梳理论证,发现干燥机出料箱下方的转阀离料仓距离较远,工艺人员加大了转阀的输送气量,导致从转阀处泄露到干燥机出料箱内的气量增大,造成出料箱内出现局部高压,引起“鼓包”现象。为了不影响干燥机密封效果,在装置建设时需要考虑干燥机和料仓之间的距离。本文的计算方法和分析结果可为此类设备的设计和生产人员参考。

进气卸荷气助力系统的设计与试验验证

介绍了排气卸荷结构存在油耗高、噪音大的问题。进气卸荷结构相比排气卸荷结构,可有效改善油耗和降低噪音,且增加系统的可靠性。对比不同的进气卸荷方案,采用多功能空气干燥器设计进气卸荷系统,通过试验验证设计的合理性。

关于PTA干燥机优化运行的研究

对PTA氧化干燥机在各种工况下的运行状况进行试验,研究了过滤机喷淋量、滤饼含湿量、干燥机蒸汽列管不凝气、进料温度、下料温度等对干燥机的影响,找出了既经济又实用的最佳操作参数,保证了干燥机在稳定条件下运行周期最长,并减少了碱洗周期。

干燥机非稳态运行模拟分析——模型的建立

根据蒸汽回转干燥机和流化床干燥机的结构特征和干燥原理,分析了两种干燥机系统主要参数的可变性以及参数波动对干燥系统的影响。分别采用边界分析和过程分析的方法,建立了两种干燥机各参数计算的数学模型,定量分析了进料量波动对两种干燥机的影响。结果表明,进料量从100%降至40%,回转干燥机的蒸汽单耗、热效率分别保持在57.9 kg/t和88.5%不受影响;流化床干燥机的蒸汽单耗从最低65.5 kg/t升高至135.7 kg/t,热效率从68.9%降低至42.9%,波动较大。

干燥机非稳态运行模拟分析——定量分析

根据计算模型,分析了蒸汽回转干燥机和流化床干燥机在进料含水率、进料温度和加热蒸汽压力三个失稳后的运行状况。结果表明,进料含水率从2%升高至4%,回转干燥机的产能降低39%、蒸汽单耗增加63%;流化床干燥机的产能降低43%、蒸汽单耗增加75%。进料温度从15℃升高至75℃,回转干燥机的产能增加67%、蒸汽单耗减少45%;流化床干燥机产能增加97%,蒸汽单耗减少57%。加热蒸汽压力从0.4 MPa(G)升高到1.6 MPa(G),回转干燥机的产能提升77%,流化床干燥机产能提升74%。

衣物干燥机的浅析

简单介绍了衣物干燥机的工作原理及分类,从电气安全方面浅析了衣物干燥机的常见质量问题,主要涉及的不合格项目有标志和说明、输入功率和电流、耐潮湿、内部布线。并对消费者如何选购合格的衣物干燥机产品以及生产企业如何降低产品不合格率提出了建议。

新型粮油烘干机的研究和开发

为改善我国粮油物料机械化烘干过程中存在的热效率不高、热风温度波动大及污染环境等问题,研发了新型粮油烘干机,对新型粮油烘干机的工艺参数、结构、高效供热装置、多重环保装置、过程监测控制等方面开展的集成化设计和创新型应用工作进行了阐述。新型粮油烘干机采用负压吸入式进风形式,工艺参数上设置不同的烘干缓苏时间比,热风风量较以往设计提高20%,控制表观风速在0.20~0.25m/s,实时监测料温以控制受热温度和时间;结构上采用全镀锌装配式结构,多段烘干和缓苏相结合工艺,变截面角状上下交错布置形式,分层进风梯度冷却方式,变频电机驱动可调节排料机构,多点进料、多点出料方式;同时采用天然气线性燃烧技术和燃烧装置供热,重力沉降和离心除尘相结合对烘干废气进行处理及多个温度传感器进行干燥过程的监测控制。实际应用表明,新型粮油烘干机具有高效、节能、低碳、清洁的特点,符合我国现代农业高质量发展的实际需求。

连续重整装置催化剂粉尘增多原因分析及对策

对中国石油长庆石化分公司600 kt/a连续重整装置催化剂粉尘增多的原因进行了分析,认为催化剂机械强度差、催化剂装填和设备安装不规范以及催化剂再生单元运行波动是造成装置粉尘增多的主要原因。采取措施:装置投用前期,做好催化剂选型工作,催化剂装卸操作标准化,加强设备管道内部检查;装置运行期间,保证催化剂稳定提升;更换再生气干燥器,监控再生气水含量;调整淘析风量,加强检查粉尘收集器,确保淘析效果;优化再生烧焦,调整再生床层烧焦温度,使其不超过565℃。通过实施上述措施,该连续重整装置反应和再生系统粉尘量未出现大幅增长,粉尘量由最高值2.1 kg/d降至1.0~1.3 kg/d,有效解决了连续重整装置粉尘增多的问题,保证了装置长周期安全平稳运行。