An Experimental Investigation of Lime Juice Drying in a Pilot Plant Spray Dryer

One of the major problems in spray drying of fruit juices such as lime juice is stickiness and thermoplasticity of their compositions. Lime juice consists of invert sugars and citric acid, which have low glass transition temperatures. Due to this characteristic, the particles stick on the dryer wall upon their collision with it. As a result, drying of these materials is very difficult. In order to solve this problem, various percent of silicon dioxide and maltodextrin (DE5), based on total soluble solid content of lime juice, have been used to reach a suitable drying condition. A cool chamber wall spray dryer was used in this investigation in order to decrease the probability of particles stickiness on the wall. Our investigation revealed that an addition of 10% silicon dioxide and 20% maltodextrin (DE5) to lime juice is the optimum amount for a complete and successful drying of lime juice. Sampling of particles from different longitudinal distances in the dryer tower is carried out to find the particle moisture contents as they fly downward in the dryer. The results show a very fast decrease in entrance moisture contents. Based on our experimental data, the variation of moisture contents are presented as a function of radial distance from central line and longitudinal distance from the entrance region.     

太阳能溴化锂吸收式制冷系统吸收特性的研究

太阳能溴化锂吸收式制冷系统的吸收器采用传热、传质分离装置,利用预冷器预先冷却和喷淋吸收的方法完成对传热、传质的分离。通过建立吸收器的计算模型,分析冷冻水出口温度、冷却水进口温度、热水温度、喷淋温度、喷淋密度等因素对传热、传质的影响。利用传热、传质分离方法,使系统的吸收特性得到强化,从而使系统获得较高的性能系数。     

喷雾热解法制备高纯超细氧化铝粉

本文以高纯硫酸铝铵为原料，用喷雾热解法制得纯度大于９９．９％、细度为１０￣２０ｎｍ的高纯超细α－Ａｌ２Ｏ３粉。探讨喷雾热解工艺条件对粉体性能的影响。     

喷射成形A356铝合金组织及力学性能的研究

采用自行开发的控制往复喷射成形专利技术,以产业化规模制备了铝合金锭坯,研究了对传统铸造A356铝合金的组织及其力学性能的影响.结果表明:喷射成形态合金组织均匀,致密度达到95.8%;挤压态合金中均匀分布大量细小Si颗粒;固溶温度为540℃,时效温度为160℃,时效10 h时硬度达到峰值,继续延长时效时间对硬度值影响甚微;经过固溶时效处理的A356铝合金常温抗拉强度σb=337 MPa,屈服强度σ0.2=281 MPa,伸长率δ5=18.3%,分别提高21.2%,35.7%,205%.     

第62届世界铸造会议宣读论文综述(有色金属部分)

详细介绍了第 62届世界铸造会议中有关有色合金铸造的 6篇宣读论文。“铝合金压铸的压力传递与铸件质量的关系”一文提出一种新的测量铝合金压铸型腔中压力传递的方法 ,搞清了压力传递、流速与铸件质量之间的关系 ,获得了本届会议的优秀论文奖。“挤压压铸和半固态铸造生产高质量、复杂的铸件”一文展示了应用压铸高技术 ,生产出力学性能极高的汽车用复杂压铸件。“监控金属型、压铸模温度的智能系统”一文提出的智能控温系统 ,测温可靠 ,能自动控制铸型温度 ,铸型中不需开冷却水孔道。“制造金属基复合材料的复合铸造工艺 (Hybrid)”一文介绍了一种挤压铸造和熔模铸造相结合生产金属基复合材料的新工艺。“喷铸法制取铝基SiCp增强复合材料的微观组织和磨耗特性”一文指出用喷铸法制取的铝基SiCp增强复合材料 ,具有很高的耐磨性能。“不同凝固条件下 ,Na ,Ca含量对加Sb变质的 3 5 6合金力学性能的影响”一文的作者通过大量试验 ,搞清了Na ,Ca的有害作用 ,指出 3 5 6合金的σb 与δ之间存在下列关系 :σb(MPa) =2 5 .87lgδ( % ) 12 8.85。     

喷射成形过程中雾化熔滴的凝固行为

通过对高温合金喷射成形过喷粉末凝固组织的分析，结合热传输分析结果，研究了喷射形过程中雾化熔滴的生核与生长动力学行为。研究结果表明：雾化过程中以异质生核为主，先凝固小颗粒与大尺寸熔滴相碰撞而成晶核在生核机制中起重要作用，不同粒度粉末均呈快速凝固枝晶生长形态，并给出了组织细化程度与冷却速度之间的定量关系。     

镁合金表面冷喷涂快凝Zn-Al合金粉末的研究

对镁合金表面冷喷涂快凝Zn-Al合金粉末工艺进行了研究，观察了涂层微观组织，并分析了涂层与基体之间的结合，测定了涂层的硬度和涂层与基体的结合强度。结果表明，采用冷喷涂技术制备的快凝Zn—Al合金粉末涂层组织致密，基体与涂层的结合处只产生塑性变形并且无熔化现象，涂层硬度比基体硬度显著提高。     

基于位置信息预测的船舶机会网络路由

机会网络利用节点移动形成的通信机会来逐步传输消息.然而当机会网络应用在海洋上时,由于海域广阔,节点分布稀疏,所以船舶之间相遇通信的概率较低,同时由于船速较慢,固定航道,传统机会网络路由协议执行效率不高.利用船舶位置信息和航行方向等,结合插值算法预测节点未来可能到达的位置,并对Spray and Wait协议改进,从而增加数据传递到目的船舶的可能性和效率,提高了船舶机会网络连通性.最后,通过仿真实验与目前比较流行的机会网络路由协议进行比较,取得较好的实验结果.     

超音速扩压器喷雾冷却数值仿真研究

为了探讨研究喷雾冷却中冷却水流量、喷射速度及喷嘴轴向分布位置等因素对超音速扩压器壁面温度的影响,借助CFD计算软件FLUENT,采用标准k-ε湍流模型,对喷雾冷却下超音速扩压器内流场进行了数值仿真。通过计算,得到了扩压器内压强分布及壁面温度分布。分析了喷雾冷却中冷却水流量、喷射速度及喷嘴轴向位置对超音速扩压器壁面温度的影响。研究表明：随着冷却水流量的增大,扩压器壁面温度降低。同时,扩压器入口处静压升高,对应仿真高度降低;减小冷却水喷射速度,可以有效降低扩压器入口处壁面温度;喷嘴的轴向分布位置对扩压器壁面温度有较大影响,仿真结果证明,喷嘴沿轴向呈对数分布有利于降低扩压器壁面温度。     

Synthesis of solid NMC622 particles by spray drying,post-annealing and lithiation

Layered lithium-nickel-manganese-cobalt oxide (NMC) cathode materials are widely used in Li-ion batteries that require high energy densities, such as those used in plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). Here we studied the synthesis of NMC622 particles by spray pyrolysis, which is a simple one-step process for production of spherical particles. However, synthesising NMC powder using spray pyrolysis has a tendency to produce hollow NMC particles. To gain insight into the mechanism behind the formation of the hollow particles, one dimensional numerical simulation of the physical and chemical phenomena taking place during spray drying were carried out. The effects of several process parameters, including drying air temperature, drying air mass flow rate, and liquid feed mass flow rate, on the evaporation and particle formation process were studied. The increased evaporation rate at higher temperatures was found to result in crust formation on the droplet surface during the particle formation, and thus, in lower solid volume fractions in the dried particles. However, by optimizing the process parameters production of solid NMC622 sulphate particles by spray drying was achieved. The produced NMC622 sulphate particles were then oxidised and lithiated in air at 850 °C via the conventional thermal treatment process. Four lithium precursors, LiOH, Li₂CO₃, Li₂SO₄ and LiNO_3, were tested for the lithiation of the oxidized NMC particles. The degree of lithiation and the crystalline phase of the powders were determined using ICP-OES and XRD, respectively.