地下水曝气过程中空气流场的数学模拟

地下水曝气（AS）过程中空气流场的数学模拟是现场过程研究的必要手段。利用饱和度与相对渗透率、毛细压力间的关系建立了AS二维非稳态流场的数学模型,用有限元法模拟了复杂流场非稳态二维气相饱和度场、速度场和稳态压力场分布,结果显示气相饱和度随着曝气时间和距曝气井位置的不同而变化。在曝气5 h左右,流场区域稳定。由饱和度的分布确定了空气在地下水中流型为下部U形,上部水平。在本模拟条件下,单井AS的影响区半径为9 m,若修复大面积污染的地下水,宜采用多井曝气的方式,增大其影响区半径。     

层间地下水污染曝气修复的影响带

影响带是开展曝气修复机理研究和工程设计的重要基础,不同场地条件下影响带的型态与形成机制不同。以我国东北地区典型层间地下水污染场地为例,在阐明污染水文地质特征的基础上,开展曝气修复的运行、监测与分析,利用地下水水位、溶解氧、温度等参数的动态变化来反映曝气修复对地下环境的影响,并以之指示曝气影响带的空间分布。进而通过对影响带地下水动态特征的分析,阐明曝气驱替过程中的水流运动过程,量化分析该层间水曝气模式下的水流运动规律。结果表明,在该曝气模式下,影响半径可达9 m,影响区呈倒圆锥状,其中赋存地下水362.04 m³,受曝气驱替作用,影响带内地下水以一定流量向四周流散,该流量随时间递减,连续运行6 h累积流散量为0.97 m³,表明该曝气修复模式下地下水的侧向流散并不显著。     

挤出过程中LDPE熔体入口流型的研究

应用流动可视化技术,考察了低密度聚乙烯熔体流径突然收缩轴对称口模时的入口收敛流型。发现在口模入口前区的两侧存在明显的环流区;环流区长度（ＬＶ）随着挤出速率和流道收缩比的增加而增大。采用前文发表的ＬＶ公式计算了实验条件下试样的ＬＶ值。结果表明,预测值与实测值之间有较好的一致性。     

曝气法去除地下水中甲基叔丁基醚的模拟研究

建立数学模型研究地下水曝气法去除地下水中甲基叔丁基醚,模型考虑了对流、分子扩散、机械弥散和相间传质等过程。在实验室中用土柱实验来模拟地下水曝气过程,分别考察了渗透率和曝气流量对甲基叔丁基醚去除效果的影响。结果显示,以粗砂为介质比以细砂为介质更有利于去除甲基叔丁基醚。以粗砂为介质,在曝气流量为0．10ms／h时,甲基叔丁基醚的去除率可达95％。模型拟合结果与实验结果吻合较好。     

液固导流管喷动流化床流型及流型转变的实验研究

以粒径为0.9mm的铜颗粒为流化颗粒,常温水为流化介质,在截面为59.2×15.6mm的矩形床中,对液固导流管喷动流化床的流型及流型转变进行实验了研究。通过对床层压降流量曲线的分析并结合实验观察,确定了液固导向管喷动流化床的流型及流型的划分,提出了流型图。研究结果对进一步开展导流管喷动流化床电极研究有重要的参考意义。     

矩形微通道内气液两相流型及其转换边界的实验研究

气液两相流流型预测是微流动系统设计和控制的基础.实验在带有“十”字形和“T”字形的矩形微通道(主通道水力直径0.29 mm)内,以氮气作为气相,分别以乙醇-表面活性剂水溶液或丙酮-表面活性剂水溶液为互溶混合液相,对气液两相流型及转换边界进行了研究.气相表观速度和混合液相表观速度分别在0.012～22.391 m·s-1...     

地下水-土壤环境中滴滴涕污染状况研究

地下水-土壤环境中滴滴涕在禁用多年后在不同地区仍有不同程度检出,已成为现代农业建设的重要影响因素之一,并且对人体健康构成潜在威胁。     

曝气吹脱处理水中的三氯乙烯的机理及动力学研究

研究了不同曝气量和曝气时间对不同浓度三氯乙烯吹脱效果和总传质系数的变化影响.结果表明,所有实验组在曝气90 min后,三氯乙烯浓度逐渐趋于稳定,且残留量不易被吹脱.在曝气60 min后,所有实验组的动力学曲线逐渐趋于水平.在曝气30 min后样品的总传质系数在同三氯乙烯浓度组中为最大值.这表明曝气吹脱可在最短时间内将绝...     

曝气生物膜反应器处理受污染河道水体实验研究

以某受污染河道水体为研究对象,设计了曝气生物膜反应器(MABR),探讨了主要污染物如COD、氨氮、TN、DO等降解及变化规律。结果表明,MABR系统运行稳定,有较高的抗冲击性能能力,对河道受污染的主要污染物有迅速的去除能力和显著的去除效果,出水水质能稳定达到GB 3838-2002地表水IV类标准。在MABR膜表面生物反应时,需添加60～80 mg/L的碳源,同时维持不高于3 mg/L的DO质量浓度,提高反硝化效果,控制TN含量;COD低于20 mg/L时,深度脱除速率下降。     

Study of Air‐Liquid Flow Patterns in Hydrocyclone Enhanced by Air Bubbles

In order to improve the oil‐water separation efficiency of a hydrocyclone, a new process utilizing air bubbles has been developed to enhance separation performance. Using the two‐component phase Doppler particle analyzer (PDPA) technique, the velocities of two phases, air and liquid, and air bubble diameter were measured in a hydrocyclone. The air‐liquid mixing pump can produce 15 to 60 μm‐diameter air bubbles in water. There is an optimum air‐liquid ratio for oil‐water separation of a hydrocyclone enhanced by air bubbles. An air core occurs in the hydrocyclone when the air‐liquid ratio is more than 1 %. The velocities of air bubbles have a similar flow pattern to the water phase. The axial and tangential velocity differences of the air bubbles at different air‐liquid ratio are greater near the wall and near the core of the hydrocyclone. The measured results show that the size distribution of the air bubbles produced by the air‐liquid mixing pump is beneficial to the process where air bubbles capture oil droplets in the hydrocyclone. These studies are helpful to understand the separation mechanism of a hydrocyclone enhanced by air bubbles.     

Ultrafiltration Fouling: Impact of Backwash Frequency and Air Sparging

A bench-scale study was performed to optimize backwash frequency and air sparging conditions during ultrafiltration (UF) for drinking water treatment in order to minimize hydraulically irreversible fouling as well as operating and maintenance costs. Surface shear stress representing different air sparging conditions (continuous coarse bubble, intermittent coarse bubble, and large pulse bubble) was applied in combination with various backwash frequencies (0.5, 2, and 6 hours) during UF of two natural surface waters. Results indicated that air sparging during permeation with intermittent coarse or large pulse bubbles significantly reduced the rate of irreversible fouling. This allowed for longer permeation times (up to 6 hours) between backwashing, when compared to a baseline condition which assumed a 0.5 h-backwash frequency with no air sparging during permeation. As a result, operation and maintenance cost savings estimated at > $350,000/year for a 29 MLD membrane train could be realized. This study demonstrates that optimized air sparging could serve as a cost-effective UF fouling control strategy for drinking water production.     

Groundwater Cleanup by In-Situ Sparging. XIII. Random Air Channels for Sparging of Dissolved and Nonaqueous Phase Volatiles

Abstract

A mathematical model is developed to simulate the sparging of dissolved volatile organic compounds (VOCs) and nonaqueous phase liquid (NAPL) from contaminated aquifers. The sparging air moves through the aquifer in persistent, random channels, to which VOC must move by diffusion/dispersion to be removed. The dependence of the rate of remediation on the various model parameters is investigated and some practical conclusions are reached regarding the operation of air sparging wells for aquifer remediation. VOCs of low water solubility (such as alkanes) and present as NAPL are found to be removed by air sparging much more slowly than VOCs of higher water solubility (such as benzene, toluene, ethylbenzene and xylenes) and present as NAPL, due to the very small maximum concentration gradients which can be maintained around droplets of the former. These small concentration gradients result in very slow rates of NAPL solution.     

Investigation of Air Flow Distribution in Small-Scale Food Products Dryer

Experimental and numerical investigations showed that the air flow velocity distribution between the shelves with identical inlet cross sections is nonuniform; in the gaps between the shelves located in the bottom part of the dryer the velocity is rather high and in the gaps between the shelves located in the middle and at the top of the dryer the velocity is low. A nonuniform air flow distribution causes unequal drying of the product; therefore, the position of shelves with the products must be periodically changed; that is, operation of the dryer is not optimal. It was revealed during numerical investigations that the use of variable inlet cross sections between the shelves gives more uniform air flow distribution. Numerically obtained air flow velocity distribution results between the shelves with the use of variable inlet cross sections were also justified experimentally.     

倾斜下降管内油气水三相流流型转变的实验研究

对倾斜下降管倾角变化对油气水三相流流型转变的影响进行了研究 ,通过大量实验得到流型图 ,发现倾角对流型转变有重大影响 :倾角增大到 3 0°时 ,增大气流量 ,泡状流已不再转变为间歇流 ,而是分层流 ;倾角变化对环状流和间歇流之间的转变影响显著。得到的界限方程规律与实验现象及流型图符合良好     

Determination of Air Flow Pattern During Solar Drying of Fruits Using a Low Range Air Speed Sensor

The solar drying is an attractive drying method in a sense of low temperature dehydration process which is useful for the dry product quality and energy saving including the environmental issues. Moreover, it can be applied in small scale (family size farms) which is in accordance with the distributed resource approach of the sustainable development. In the course of the recent research numerous drying experiments were elaborated with the solar drying of biomaterials, mainly with fruits. Beside the measurements, the modelling of the drying process was also investigated. Special attempt was carried out developing a low range air speed sensor (for measuring natural ventilation during the solar drying process) which can be used with a usual data logging system. After choosing the working principle a one dimensional prototype of the sensor was developed and constructed. Based on the measurements the optimal setting of the sensor was determined. Additionally, the set-up of a two-dimensional sensor prototype is also presented, along with its first measurement results.     

矩形微通道内气体-互溶混合液体两相流流型的实验研究

在包含了“十”字形和“T”形结构的微通道系统内,以氮气、丙酮(或乙醇)及质量分率0.5％农面活性剂poloxamer 188的水溶液为实验介质,在气相表观速度为0.004～2.191 m/s,水溶液表观速度为0.056～0.281 m/s,溶剂(丙酮或乙醇)表观速度为0.017～0.086 m/s时,利用可视化观察与压...     

三相流环状集输管网流型研究

油气水三相流动广泛存在于石油和天然气开采过程中,因此对油气水三相流流动型态的觃律迚行研究是热力计算模型和油田集输管道水力的基础,也为解决油田中混输问题提供了重要的实用价值及经济效益。以大庆低渗透油田第八采油厂三矿7#--4计量间环2作为试验环路迚行CFD数值模拟,按照油气水三相流的不同油水界面特征、气液界面特征最终划分为4种流型,并模拟了不同含油率、不同含气率、不同速度条件下的流型,得到了不同条件下流型图及流型变化觃律。这为外围油田环状集输管网的流程运行探索了新的途径,为实现环状集输管网设计计算提供理论支撑。     

化学实验室空气中颗粒态汞检测与污染特征研究

在高校区(常州工程职业技术学院)选定3个典型的化学实验室,采集室内空气中的可吸入颗粒物,用湿式消解法提取后采用原子荧光光谱法测定颗粒态汞浓度。检测结果表明:化学实验室空气中颗粒态汞浓度未超过《工作场所有害因素职业接触限值》和《车间空气中汞卫生标准》规定值,但却超过《工业企业设计卫生标准》(tj36-79,居住区)规定的浓度标准,说明化学实验室空气存在一定的汞污染。不通风情况下实验室空气中颗粒态汞浓度接近于通风情况下的10倍,说明化学实验室汞污染主要来源于含汞化学试剂,良好的通风条件有利于降低颗粒态汞污染。初步判断气粒转化二次生成的颗粒态汞是颗粒物中汞的主要来源。