操作条件对DTB流化床结晶器内CFD状态的影响

运用计算流体力学方法对DTB流化床结晶器内循环流量对流体悬浮状态的影响以及不同粒径颗粒在出口处固体质量流率的变化情况进行模拟.模拟结果表明,保持进料流量一定的情况下,外循环流量与进料流量的比值也对结晶器内流体的体积分数分布情况有着显著的影响,然而,循环流量的加大也会增加结晶器内颗粒的碰撞与破碎的几率,不利于晶体的成核与成长.另外一组模拟结果还表明,不同粒径的颗粒在各出口处的质量流率差异明显,本模拟条件下,粒径为0.5 mm以下固相颗粒基本上由循环出口排出,而粒径0.5 mm及以上的固相颗粒则能够在导流筒与档板之间循环流动,这意味着在一定条件下,能够控制一定粒径的颗粒在结晶器内的悬浮流动,这对于控制一定粒径范围的晶体的成核与成长有着重要的作用.     

敞口式DTB结晶器

本文介绍了敞口式ＤＴＢ结晶器，并通过试验验证，结果能符合要求。     

利用DTB结晶器生产优质光卤石的探讨

根据对光卤石结晶条件的分析，满足光卤石结晶的循环流量、生产强度、料液温度、悬浮密度及晶体生长的过饱和度分布和晶体分级形式，才能保证光卤石粗粒晶体的形成。将真空结晶器改造为DTB结晶器，DTB结晶器以其独特的结晶功能，能有效地生产优质的光卤石晶体，提高了光卤石的质量及取得率。同时进行投资测算，说明DTB新技术的优势。     

DTB结晶器在晶体氯化镁生产中的应用分析

在以提溴母液为原料的氯化镁生产中,硫酸镁及氯化钠等杂质直接影响产品质量,经过试验利用DTB结晶器生产晶体氯化镁可以有效降低产品杂质含量,产品中六水氯化镁含纯99%以上,达到食品添加剂标准,提高了产品档次,增加了企业效益。     

敞口式DTB结晶器

本文介绍了敞口式ＤＴＢ结晶器，并通过试验验证，结果能符合要求     

晶体在多维流化床连续结晶器中的共存与分级

将流化床成功地应用于连续结晶的基本条件是保证不同粒度的晶粒在流化床中的共存并实现它们的分级悬浮。文中讨论了多维流化床中的大小颗粒共存的优势、颗粒的混合状态以及影响其颗粒分级悬浮的主要因素，认为多维流化床中可实现多粒度颗粒的共存，并通过对各种影响因素的研究，可最大限度地实现分级悬浮，设计出有效的多维流化床连续结晶器。     

真空结晶器中加强圈的设置与理论计算

真空结晶器属于外压容器,在使用过程中,经常因刚度不足而导致失效,使容器失去了原来的形状,从而影响生产的正常进行.正确地设置加强圈,可有效地解决此问题.文章主要介绍了真空结晶器中设置加强圈的方法和理论依据.     

外循环蒸发器设置热泵的应用效果

外循环蒸发器的工作原理与降膜式蒸发器的工作原理不同,它是在加热蒸发过程中靠料液的密度差形成循环并蒸发,要求加热温度较高,加热温差较大,加热壳程一般是正压加热,它是间断进料间断出料。如果在蒸发器中引入热泵抽吸二次蒸汽作为一部分加热热源,通过计算看其节能效果怎样。仅以WXZQ02-1200型双效循环蒸发器在骨头汤生产中的设计及应用为例进行阐述     

计算流体动力学(CFD)在食品工业中的应用

计算流体动力学(CFD)是一种强有力的模拟工具,主要利用计算机和数值计算方法模拟流体流动。文中结合具体实例,概括了近年来CFD在食品工业中的应用现状,介绍了在食品工业常用的几种CFD软件,并展望了其在食品工业中的发展与应用前景。     

计算流体动力学在短驻留涂布过程中的应用

介绍了流体动力学的一种新的研究方法－计算流体动力学方法，及其在造纸工业短驻留刮刀涂布过程中应用的结果，这里报告的计算结果包括涂布头流体动力学参数的描述以及它们的分布情况；涂布过程的操作条件对这些参数的影响规律。研究发现，在该过程中存在的一个主旋涡和多达二级旋涡会导致该涂过程的不稳定，同时造成该涂布方式成纸质量较差。     

计算流体力学(CFD)在制盐行业中的应用及前景

介绍了制盐相关行业在CFD研究实践方面的工作。提出了在制盐行业的搅拌槽设计、轴流泵叶轮设计、洗盐工艺、提高传热效率、干燥床设计、结晶控制及结晶器设计等方面开展CFD研究的方向。指出了国内盐行业开展CFD研究的制约因素。积极开展计算流体力学研究,是制盐行业节能降耗,实现产业升级的重要途径。     

Analysis of Thermal Processing of Table Olives Using Computational Fluid Dynamics

In the present work, the thermal processing of table olives in brine in a stationary metal can was studied through computational fluid dynamics (CFD). The flow patterns of the brine and the temperature evolution in the olives and brine during the heating and the cooling cycles of the process were calculated using the CFD code. Experimental temperature measurements at 3 points (2 inside model olive particles and 1 at a point in the brine) in a can (with dimensions of 75 mm × 105 mm) filled with 48 olives in 4% (w/v) brine, initially held at 20 °C, heated in water at 100 °C for 10 min, and thereafter cooled in water at about 20 °C for 10 min, validated model predictions. The distribution of temperature and F‐values and the location of the slowest heating zone and the critical point within the product, as far as microbial destruction is concerned, were assessed for several cases. For the cases studied, the critical point was located at the interior of the olives at the 2nd, or between the 1st and the 2nd olive row from the bottom of the container, the exact location being affected by olive size, olive arrangement, and geometry of the container.     

黑液碱回收系统计算流体力学模拟研究最新进展

目前,提高入炉黑液固含量是碱回收系统的发展趋势,采用计算流体力学(CFD)技术可以预测碱回收过程黑液的流动特性及其雾化燃烧性能。本文归纳了碱回收系统黑液雾化和燃烧数值模型,重点阐述了碱回收系统黑液雾化和燃烧的数值模拟研究进展,总结了等温和非等温模型在碱回收系统黑液燃烧中的应用,提出进一步完善黑液燃烧模型并开发简化子模型以实现黑液雾化和燃烧数值精准模拟的研究,以期为高固含量黑液碱回收研究提出新的攻关方向,最后对碱回收技术的未来发展进行了展望。     

非通风状态新型地下粮仓储粮温度场的CFD数值模拟

地下粮仓储粮温度场是保证储粮品质和绿色生态储粮的重要影响因素。针对地下粮仓试验仓,该文利用Gambit软件建立了地下粮仓的三维立体模型,并对模型进行了网格划分,采用CFD数值模拟方法研究了非通风状态地下粮仓粮食储存过程中粮堆温度场的变化规律。通过编写和导入UDF函数,改进CFD软件中的质量控制方程、动量控制方程和壁面热量传递控制方程,通过迭代计算和基于CFD软件模拟得到了地下粮仓非通风状态条件下温度场的变化规律,研究结果表明,随着地下仓储粮时间的变长,仓内粮堆温度与周围维护结构之间、粮堆之间不停的进行着热质交换,最终温度逐渐趋于当地地下恒温温度值附近,地下仓可以作为一种经济适用的仓型来推广;同时,本文的研究可以为地下粮仓的温度场控制提供参考和依据,为粮堆机械通风手段作为参考。     

Development and validation of Computational Fluid Dynamics models for precision structural fumigation

Three-dimensional Computational Fluid Dynamics models for structural fumigation were developed and validated using Fluent^® based upon comprehensive data sets collected during the fumigation of a commercial flour mill. The external flow model, which included the flour mill and surrounding structures, was used to predict stagnation pressures on the mill's walls as a function of the wind speed and direction data. The pressure differences due to density differences between the gas inside and the air outside the mill (stack effect) were estimated using the environmental temperature and relative humidity data. The combined effect of the stagnation pressure and the stack effect was used as the boundary conditions of the internal flow model. The internal flow model incorporated interior details of the mill such as building plans, locations of major equipment, partitions and ducting. Because it was not possible to obtain the actual number and sizes of the cracks in the structure envelope, the idea of representing the cracks as effective leakage zones (ELZ) was adopted. The flow resistance coefficient, k_L, of the ELZs determines the gas tightness of the mill. Nine simulations were conducted with different k_L values. Both experimental and simulation concentration data indicated that the fumigant was uniformly distributed within the entire mill building. Using a manual optimization approach, one specific k_L value was determined for which the models were able to yield a half-loss time (HLT) value identical to the experimental HLT (17 h) and minimize the prediction of the concentration×time (Ct) product to within 10.5% of the observed value. Therefore, it was concluded that the models were validated and the assumption of ELZ was reasonable. The modeling methodology established in this paper could be utilized for the prediction of fumigation performance in any type of structure.