Ventilation system for drying out buildings after a flood: Influence of the building material

Portugal’s most striking buildings were usually built near waterways and on floodplains due to easier access to water supply. This proximity, besides causing an increased probability of pathologies due to rising damp also brings a higher exposure to the risk of flooding. After the occurrence of a flood, all building elements below the flood water level will remain with high water contents, with all the negative consequences that this fact can cause, namely, the degradation of the materials. Therefore, it is very important to promote the fast drying of these building elements to prevent worse consequences, either structural, safety, or heritage conservation. In a recent investigation undertaken under a collaboration project involving the University of Coimbra and University of Porto, an innovative treatment system to combat rising damp in historical buildings was developed: the wall-base ventilation system. Currently, investigations have focused on analyzing the technical feasibility of adapting this system for drying out walls of historical buildings after floods.     

多孔材料热风干燥过程中力学特性分析

为了得到高品质的干制品,基于黏弹性理论和Maxwell固体特性,建立了多孔材料干燥过程中黏弹性应力数学模型。采用MATLAB编程的方法对马铃薯热风干燥过程中内部各单元层干燥应力进行数值模拟计算。计算结果表明:随着干燥过程的进行马铃薯各单元层产生干燥应力为压应力且逐渐增大,达到最大值后开始减小;当压应力减小到0时出现应力反向现象,各单元层应力由压应力变成拉应力,拉应力逐渐增大到最大值后开始减小直至达到平衡不再发生变化。在整个热风干燥过程中干燥过程中,内单元层干燥应力值总是大于外单元层应力值,且表单元层的干燥应力始终为0。通过实验对模型进行验证,验证结果表明此模型可以用来表述干燥过程中多孔材料内部应力变化和分布规律。     

进风量对燃气燃烧器燃烧及NO_x排放特性影响

运用Fluent软件对40 t/h锅炉用燃气燃烧器的性能进行三维数值模拟。首先用Pro/E软件画出燃气燃烧器和炉膛三维图,然后在Gambit中进行建模,采用相关数学模型,在Fluent中设置边界参数及初始条件,迭代计算得出结果。研究了燃烧器的总体性能,燃烧器及炉膛内部甲烷、空气、压力、温度分布云图。着重研究了进风量过大或过小时对燃烧器及炉膛内速度场、温度分布、NOx排放量的影响。结果表明:合适的进风量是保证燃烧器稳定燃烧的关键因素之一,对污染物NOx的排放也是关键的影响因素。数值的模拟计算结果对燃烧器优化设计改造提供了重要的研究依据。     

Effect of airflow rate on drying air and moisture content profiles inside a cross-flow drying column

Rice at 20.5 and 16.3% initial moisture contents (IMCs) was dried using 57°C/13% RH air at airflow rates (Qs) of 0.36, 0.46, and 0.56 (m³/s)/m² for 30, 60, and 90?min, respectively, in an experimentally simulated cross-flow drying column. Q significantly affected the drying air and rice moisture content profiles within the drying column; for a particular drying duration, the range of MCs within the column decreased as Q increased. Q also impacted the extents of intra-kernel material state gradients created and thus had potential impacts on kernel fissuring and consequent head rice yield reduction. In addition, the impact of Q on the above-mentioned profiles was dependent on the rice IMC.     

干燥工艺对聚酯薄膜透明度的影响

对BOPET生产中的干燥工艺进行了介绍,对干燥空气露点、流化床温度、干燥塔温度对聚酯薄膜透明度的影响进行了分析,并提出了高透明聚酯薄膜生产的最佳干燥工艺。     

空冷器对吸收稳定系统的影响

为保证吸收塔的吸收效果,进而保证产品质量,分析了影响吸收效果的因素,找出了进入吸收塔的压缩富气温度是主要影响因素,提出应将空冷器电机改装为变频电机,可控制进入吸收塔压缩富气的温度,既节能,又方便操作。     

通风和座舱空气过滤器试验标准的最新进展

主要介绍了通风用空气过滤器和座舱式空气过滤器两个不同类型的空气过滤器的试验方法和标准,重点介绍了各试验方法和标准的区别,阐述分析了目前国际的现状和国内普遍存在的问题,最后介绍了目前座舱式空气过滤器的发展,为进一步研究提供参考。     

自然通风式造粒塔风门开度对出塔粒子温度影响的研究

简述了影响自然通风式尿素造粒塔出塔粒子温度的主要因素;进行了熔融尿液降温、结晶、冷却过程的热量平衡计算和调节造粒塔风门开度的工厂实验。研究结果表明,自然通风式尿素造粒塔可以根据自然条件的变化,通过热量平衡计算调节风门的开度,达到降低出塔尿素粒子温度的目的。     

给定曲线的远红外烘干微机控制系统研究

研制了远红外烘干微机控制系统。该系统采用PC机作为上位机，运用可视化编程语言VB6．0设计出友好的人机操作环境，整个系统能按照操作人员在PC机上绘制出的干燥工艺曲线进行干燥作业，实现干燥过程的自动控制，从而可减少寻找最佳干燥工艺曲线的时间及人力与物力。系统还具有数据动态显示和自动存储等功能。经现场使用表明，该系统工作稳定可靠、操作简单方便，确保了物质烘干质量的提高。     

CO2跨临界循环特性对热泵干燥系统的影响

对CO2跨临界循环的超临界放热特性和运行规律进行了分析,根据这些特性,对其应用于干燥热泵系统进行了探讨,并对蒸发温度、过热度及气体冷却器出口温度对系统除湿率的影响做出分析。研究表明CO2跨临界循环放热段存在大的温度滑移,气体冷却器出口温度低有利于系统运行,这些特点非常适合干燥系统,而且干燥系统除湿率也受到这些特性的影响,系统存在最优运行压力和最佳的蒸发温度与气体冷却器出口温度组合。     

Analysis of a piston PSA process for air separation

The piston driven PSA process offers the potential for achieving productivity improvement by rapid piston action. In the present work, experiments were performed on a laboratory scale piston driven PSA test rig with provisions to vary all the important operating variables, namely, phase angle configuration, stroke length, cycling speed duration and angles of feed introduction and product withdrawal. Air separation on 13X zeolite was chosen as the model experimental system. Experiments with adsorbent particles of two different sizes confirmed that mass transfer resistance is important and may significantly affect the separation performance. A mathematical model was developed to simulate the process. The numerical solution was verified by simulating limiting conditions that had analytical solutions. Some basic model assumptions related to piston motion were verified by comparing with experiments conducted at well-defined limiting conditions like empty column and total recycle. Flow resistance in the connecting tubes seemed to explain the observed difference in both phase and amplitude of the pressure profiles measured at the two ends of the column. The model predictions were generally in good agreement with the experimental observations. The model was used to perform a parametric study in the operating regions that were not covered in the experiments. General inferences are made regarding the operating configurations that are expected to improve system performance.     

Influence of process variables on the drum drying of mango pulp

Response surface methodology was used to evaluate the best process conditions in the drum drying of mango pulp regarding the physicochemical properties and nutrients content. The independent variables in the central composite rotatable design were: temperature (119–151°C) and residence time (9–41?s), while the concentrations of process additives used were: 3% corn starch and 0.5% glyceryl monostearate. Mathematical models for moisture content, total carotenoid content, and color parameters of the reconstituted pulp (a*, Hue, and ΔE) were obtained. The optimized conditions were combinations of residence time between 10 and 25?s, and temperature from 120 to 135°C, in which the flakes showed moisture content ranging from 2 to 5%, besides a more intense yellow color and total carotenoid retention between 90 and 96%.     

基于TE过程的仿真系统的实现

TE过程是对一个化工过程的真实模拟,被广泛用于过程控制研究。针对TE模型,设计了基于MATLAB、Excel和力控的仿真系统。该仿真系统用MATLAB设计控制算法进行仿真,用力控实现复杂、友好的图形界面,Excel作为MATLAB和力控的数据库。MATLAB和Excel通过ExcelLink进行数据链接,Excel和力控通过DDE进行数据交换。该仿真系统已投入使用,为研究过程控制提供了良好的基础平台。     

燃煤高洁净度干燥介质直接发生系统研究

针对我国的燃料资源特点以及改善干燥工艺经济性的需求，开发了一种以原煤为燃料的直接式干燥介质发生系统。该系统通过机械化给煤、区域控温、多次进风等技术手段实现原煤的脱硫和稳定、高效、高温燃烧，通过多级旋涡凝聚式高温烟气除尘装置实现烟气的净化，通过控温、混风、配风最终得到温度和风量大幅度精确可调的高洁净度干燥介质。与其他干燥介质发生系统相比，该系统可以使生产成本下降20％～50％，可以有效地控制干燥介质中烟尘和硫化物含量，可以用于对纯净度没有过高要求的各种干燥工艺过程。介绍了这种干燥介质发生系统的工艺原理、应用效果、适用领域和发展前景。     

10万t／aPVC旋流干燥工艺的改进

介绍了某公司对PVC干燥工艺进行改进的具体措施：更换1#风机叶轮,在1#螺旋输送段加装螺旋输送叶片并调整螺距,拆去1#风机进口空气过滤器,断开20旋风分离器排风管与气流床的连接,改变罗茨风机主动轮、辅动轮直径,在C102抽吸风机排风口加装1组旋风分离器。改造后共减少经济损失约140万元／a。     

刮膜式分子蒸馏过程的研究

对刮膜式分子蒸馏传热方程进行数值求解,针对0 25m2 刮膜式分子蒸馏器,以DBP(邻苯二甲酸二正丁酯)为物料进行了模拟计算。初步探讨了进料温度、进料速率2个参数对蒸馏器内头波温度及液膜表面蒸发速率的影响。模拟结果表明,头波温度随进料温度的升高而升高、随进料速率的增大而降低;液膜表面蒸发速率随进料温度的升高而增大,随进料速率的增大而减小。     

Stability and performance of a spouted bed in drying skimmed milk: Influence of the cone angle and air inlet device

This paper investigates the skimmed milk drying over inert particles in a 30?cm diameter spouted bed. Drying was evaluated for conical bases of three cone angles (45°, 60°, and 75°) operating with 4.5?kg of inert particles, and two air inlet devices with different geometries—a Venturi-type nozzle and a straight section pipe. The drying capacity was evaluated from the maximum paste feed rate that allowed stable operation and spouting dynamic behavior throughout drying. It was observed that drying capacity and dynamic stability were greatly affected by the cone angle and the inlet device geometry. From the conditions evaluated, the best configuration with regard to the drying capacity was obtained for the 45° conical base using the Venturi-type inlet device. In this dryer, a rate of 40?mL/min of skimmed milk was processed and a powder with a moisture content of about 10% was produced. The good performance on this configuration was attributed to several factors that affected positively the solid circulation rates and the dynamics stability. Such factors include the operation under a higher static-bed height, the spouting on conical configuration, and the improved aeration of the annular region provided by the inlet device. At this configuration, and for paste feed rates up to the maximum admissible value, the spouted-bed dynamic was almost not affected by the liquid and the wet bed operated under dynamic conditions very similar to those of the dry bed. Using a 75° conical base with the Venturi-type inlet device under a slightly lower drying capacity (35?mL/min) also resulted in quite stable dynamic conditions. The 60° conical base with the Venturi-type device was the configuration that performed worst with regard to drying capacity (30?mL/min).     

混煤燃烧过程中的交互作用:过量空气系数对混煤燃尽特性的影响

在沉降炉上对无烟煤、贫煤、烟煤、褐煤以及不同配比(25%、50%、75%)混煤开展了过量空气系数对混煤燃尽特性影响的实验研究。结果表明,混煤燃烧中挥发分高的煤对挥发分低的煤存在促进和抑制2种交互作用。"炉外"掺烧方式下,低挥发分煤与高挥发分煤掺混时,抢风抑制作用表现明显;尤其是掺烧75%高挥发分煤时,抢风抑制作用最为显著;提高过量空气系数可以改善贫氧气氛,减弱混煤燃烧中的抢风抑制作用,提高混煤燃尽率。"炉内"掺烧方式下,过量空气系数的增加,交互作用减弱,各单煤的燃烧独立性增强,混煤燃尽率逐渐接近计算线性燃尽率。     

共沸脱水法干燥灭多威肟新技术研究

介绍采用共沸脱水原理进行灭多威肟干燥的新方法。将30.0g湿品灭多威肟,100.0ml二氯乙烷加入到旋转蒸发器中,减压将溶剂蒸出,得到干燥的灭多威肟产品,水分<0.3%,干燥损失<0.3%。