负载型多分散气溶胶在管道内的传输规律

放射性气溶胶的传输一直是倍受关注的环境问题。为研究放射性气溶胶在管道内的传输规律，首先自制了能够产生稳定的、多分散气溶胶的发生器。主要考察了稀释气流速（5~25 L/min）、气溶胶颗粒粒径（多分散体系）及固体颗粒密度（土壤、石英砂）对气溶胶在管道内传输的影响。即考察了粒径多分散的石英砂、土壤颗粒形成的气溶胶及表面负载Ag的石英砂颗粒模拟负载型放射性气溶胶，在不同稀释气流速作用下进入管道内的传输，针对每一节管道内的沉积物进行收集分析，从而得到气溶胶在管道内的传输及沉降规律。研究结果表明：密闭管道内，在一定流速范围内，沉积物最高频度粒径随着管道距离的增长而先增大后减小；小粒径的颗粒在传输过程中自重沉降，且由于布朗运动吸附在大粒径颗粒物表面加速其沉降速率，即减小了其在管道内的传输距离；表面负载Ag的石英砂颗粒形成的气溶胶随着稀释气吹扫导致Ag和石英砂颗粒之间有不同程度的分凝，气流速率越大，分凝现象越明显。     

不同尺寸管道中细颗粒的沉积运动规律研究

研究不同尺寸管道中颗粒物的运动沉积情况,对于采用合理管道,以减少管道中的颗粒物具有重要价值。利用流体分析软件模拟不同尺寸管道内水介质中细颗粒物的沉积运动规律,得出管道尺寸对细颗粒物沉积运动的影响。结果表明:流体在管道中流动的过程中,壁面附近的流体流速低于管道内部流体流速,壁面附近的压力高于管道内部;流体在管道运动过程中,逐渐发展完全,压力与流速在后半段趋于稳定。在管道直径一定的情况下,颗粒物沉积率随管道长度增大而增大;在管道长度一定的情况下,颗粒物沉积率随管道直径增大而减小;当管道长度较短且管道直径较大时,颗粒物沉积现象不明显;当管道管径同时变化时,对颗粒物沉积产生综合影响,变化规律非线性。     

严重事故下多组分吸湿性气溶胶的重力沉降研究

严重事故时,安全壳内的多组分吸湿性气溶胶将在高湿度的条件下吸水增大,从而影响其重力沉降行为。通过理论分析,本文推导了多组分吸湿性气溶胶颗粒平衡粒径的物理模型,并通过实验结果进行验证。该模型重点关注溶解度对吸湿过程的影响,解释了多组分吸湿性颗粒粒径增大曲线不连续的原因。同时,分析了典型千兆瓦级压水堆核电厂中相对湿度、干粒径及非吸湿性组分质量分数对重力沉降去除系数的影响。结果表明,只有当气溶胶颗粒增大到一定程度后,其重力沉降速度才会明显的提高;对于干粒径超过0.01 μm的纯吸湿性气溶胶颗粒,只有超过一定湿度后其才会因吸湿而加速沉降,且该湿度下限随着干粒径的增大而减小;随着事故的进行,气溶胶颗粒中的非吸湿性组分质量分数逐渐增加,上述湿度下限将增加,且同湿度下吸湿对重力沉降的促进作用减弱。      

不同通道内超临界水中颗粒物的运动沉积特性研究

利用ANSYS CFX软件模拟,采用κ-ε模型来预测通道内的湍流变化,得到不同粒径(1～10μm)颗粒在不同管道内超临界水中的运动沉积特性规律。发现不同管道中细颗粒物的运动沉积浓度在不同入口温度下,大致呈现"M"型分布,在靠近管道附近存在颗粒物浓度的极值。不同入口速度条件下,低速时各管道中颗粒浓度分布非常离散,速度提高后各管道内的颗粒物浓度呈现各自分布特点,主要受到颗粒扩散、热泳力、湍流作用及二次流等影响。分析出颗粒的运动沉积主要是颗粒与水分子间动量交换,以及颗粒运动受到阻力综合作用的结果。     

不同颗粒度188Re-硫化铼混悬液的制备及其稳定性研究

以两种分散方法制备不同粒径分布的188Re-硫化铼混悬液,采用涡旋法制得的大颗粒混悬液,粒径大于5 μm的颗粒占55%,大于10 μm的占19%;超声法所得混悬液粒径小于5 μm颗粒占93%,大于10 μm的只占0.3%.两种方法所得混悬液粒径分布有显著差异(P<0.01).稳定性测试结果表明,涡旋法所得混悬液在6 min内稳定可靠,超声法所得混悬液在15 min内能均匀分散,此后取药需重新分散,且药物仍然均匀可用,颗粒度和放化纯度无明显变化.采用涡旋分散装置制备大颗粒混悬液时,操作简便,结果重现性良好,并同时避免了涡旋分散过程中因手动操作对人体造成的辐射损伤,减少了人为因素对颗粒度的影响.     

上海市钢铁工业尘单颗粒分析

用高分辨率、高灵敏度的扫描质子微探针对上海市工业尘进行单颗粒分析,研究了在颗粒物中不同元素的分布以及元素平均含量随粒径大小的变化。结果表明,Fe、Cr、Mn等元素在颗粒物中均匀分布的,而K、Ca则富集在颗粒物的表面。而且这些元素的平均含量随粒径的变化呈现出一规律性,其中大部分重金属元素（如Cu、Cr、Ni、Zn、Pb）聚集在颗粒粒径＜5μm的颗粒物上。     

单颗粒大气气溶胶的同步辐射微束X射线研究

在北京同步辐射装置4W1B光束线的荧光站,用束斑大小为20 μm×10 μm的X射线微束分析了污染排放源PM10单颗粒和环境空气监测样品PM10单颗粒,得到了单颗粒的X射线荧光谱。实验结果表明,来自不同污染排放源的颗粒物,它们的能谱具有明显的特征,根据颗粒物的能谱可以识别颗粒物的来源。     

金属铱多孔材料过滤性能分析

金属多孔材料因其良好的过滤和理化性能，在气-固分离方面得到广泛的应用。采用氦质谱检漏仪、扫描电子显微镜及比表面积测试仪等对金属铱多孔材料的孔隙率、微观结构、孔隙特征及孔隙分布等方面进行了研究。研究表明，该金属铱多孔材料由粉体颗粒和孔隙组成，其内部孔隙相互连通构成复杂的三维结构；孔隙率约为16.93%，有98.7%的孔隙孔径为0.002~0.05 μm，1.3%的孔径为0.05~0.46 μm；根据多孔材料微过滤理论及气体中微粒捕集理论（不考虑多孔材料厚度），该金属铱多孔材料对粒径不小于0.46 μm粉体颗粒过滤效率达100%，且不受气体流速的影响；对粒径小于0.46 μm的粉体颗粒，当气体流速不大于5.28 m/s时，过滤效率同样达100%，而当气体流速大于5.28 m/s时，则会有部分粉体颗粒通过。多孔材料微过滤理论及气体中微粒捕集理论可为多孔材料过滤性能评价提供参考，该金属铱多孔材料也可用于放射性同位素材料的气-固分离。     

γ辐照和热作用下硅基磷钼酸铵对Cs的吸附行为

采用旋转蒸发减压法将磷钼酸铵（AMP）担载入多孔SiO₂中制备复合吸附剂,研究了其在⁶⁰Co γ辐照、温度、共存离子等条件下对Cs(Ⅰ)的吸附性能影响。结果表明：吸附剂粒径为90 μm,平均孔径18 nm;400 ℃附近AMP发生明显的热解反应,（2 2 0）晶面的21.62°峰强减弱,同时检测到MoO₃的产生。γ辐照会引起部分AMP由晶相转变为非晶相,经计算在吸收100 kGy剂量后吸附剂是平均晶粒尺寸为383Å（1 Å=0.1 nm）、边长为11.6 Å的正方体晶胞,但辐照对Cs(Ⅰ)的饱和吸附容量和分配系数的影响较小。吸附剂在0.1~7.0 mol/L HNO₃的模拟废液中对Cs(Ⅰ)的吸附选择性强,吸附过程为离子交换、符合Langmuir吸附模型。     

衡阳市大气颗粒物中~(210)Po的活度-粒径分布测量

利用大流量撞击式分级采样器、放化分离提纯技术和α谱仪测量技术,建立了针对大气颗粒物中210Po的活度及活度-粒径分布的测量方法,并应用该方法分别于春季和秋季对衡阳市城区大气颗粒物中210Po的活度及活度-粒径分布进行了测量。实验测量结果表明,衡阳市城区大气颗粒物中210Po的含量处于正常水平;总体积比活度和质量比活度的分布范围分别为:0.012 5 m Bq·m-3~1.165 8m Bq·m-3、0.459 7 Bq·g-1~13.859 8 Bq·g-1,体积比活度含量占TSP中总含量93%的210Po存在于粒径范围小于3.0μm(PM3.0)的颗粒物中;雾霾天气会提高公众所接受的天然内照射剂量;同时发现雨水对大气颗粒物中210Po的净化作用较为明显。     

A calculation methodology proposed for liquid droplet impingement erosion

Bent pipe wall thinning has been often found at the elbow of the drain line and the high-pressure secondary feed-water bent pipe in nuclear reactors. Liquid droplet impingement (LDI) erosion could be regarded as one of the major causes and is a significant issue of the thermal hydraulics and structural integrity in aging and life extension for nuclear power plant safety. In this paper a computational methodology is established for simulation of LDI erosion using computational fluid dynamics (CFD) simulation and theoretical calculation. Two-phase flow numerical simulations are conducted for standard elbow geometry, typically with the pipe diameter of 170 mm. This computational fluid model is built up by incompressible Reynolds Averaged Navier–Stoke equations using standard k–? turbulence model and the SIMPLE algorithm, and the numerical droplet model adopts the Lagrangian approach. The turbulence damping in vapor–droplets flow is theoretically analyzed by a damping function on the energy spectrum basis of single phase flow. Locally, a droplet impact angle function is employed to determine the overall erosion rate. Finally, the overall and local investigations are combined to purpose a general methodology of LDI erosion prediction procedure, which has been complemented into CFD code. Based on our more physical computational results, comparison with an available accident data was made to prove that our methodology could be an appropriate way to simulate and predict the bent pipe wall thinning phenomena.     

A numerical study on turbulence attenuation model for liquid droplet impingement erosion

The bent pipe wall thinning has been often found at the elbow of the drain line and the high-pressure secondary feed-water bent pipe in the nuclear reactors. The liquid droplet impingement (LDI) erosion could be regarded to be one of the major causes and is a significant issue of the thermal hydraulics and structural integrity in aging and life extension for nuclear power plants safety. In this paper two-phase numerical simulations are conducted for standard elbow geometry, typically the pipe diameter is 170 mm. The turbulence attenuation in vapor-droplets flow is analysed by a damping function on the energy spectrum basis of single phase flow. Considering the vapor turbulent kinetic energy attenuation due to the involved droplets, a computational fluid dynamic (CFD) tool has been adopted by using two-way vapor-droplet coupled system. This computational fluid model is built up by incompressible Reynolds Averaged Navier–Stoke equations using standard k–ε model and the SIMPLE algorithm, and the numerical droplet model adopts the Lagrangian approach, a general LDI erosion prediction procedure for bent pipe geometry has been performed to supplement the CFD code. The liquid droplets diameter, velocity, volume concentration are evaluated for the effects of carrier turbulence attenuation. The result shows that carrier turbulence kinetic energy attenuation is proved to be an important effect for LDI erosion rate when investigating the bent pipe wall thinning phenomena.     

水滴粒径对旋叶式汽水分离器性能的影响

采用计算流体动力学技术计算分析了水滴粒径对旋叶式汽水分离器性能及其内部流动细节的影响。采用Euler双流体模型结合均值粒径方法计算了分离器内两相流动,粒径选取范围为0.1～150 μm;通过分析流场细节揭示了粒径与分离器性能的内在关系。结果表明：随粒径的增大,压损呈先升后降趋势,分离效率呈“S”型增大趋势;对分离效率产生影响的粒径范围为5～150 μm,而对压损产生影响的粒径范围为大于5 μm;与试验值相比,计算所得压损相对偏差均在4.8%以内,且选用合适的粒径能获得较为准确的分离效率和出口湿度,表明本文计算方案较为可靠;蒸汽流量分配比和水分返流比均随粒径的增大而减小,而返流水分占出水总量的比例较高,可达48%,因此计算中必须加以考虑,建议计算域中加入外围空间。     

杯式连续沉淀器中草酸亚铁的沉淀工艺

采用着色法研究了杯式连续沉淀器中流场形状与性质，并采用加入颗粒、即时沉淀反应生成颗粒两种方式考察了沉淀颗粒在中心涡流区域的分布与扩散情况。在26 ℃时，采用杯式连续沉淀器研究了料液的加料方式、搅拌速率、表观反应时间等因素对生成的草酸亚铁沉淀颗粒粒径分布和平均粒径、对连续沉淀器和搅拌桨表面颗粒粘结的影响。当草酸料液与硫酸亚铁料液均从杯式连续沉淀器中心涡流区域加入时，可以有效避免沉淀器内壁产生颗粒粘附、结块现象，且所生成的颗粒平均粒径较大，其中生成的粒径为2～5 μm和小于10 μm的颗粒所占比例较小。当搅拌速率在500～800 r/min时，提高搅拌转速不利于生成粒径为2～5 μm和小于10 μm的沉淀颗粒，而草酸亚铁连续沉淀反应的表观反应时间大于30.0 min时，沉淀颗粒的生长速率逐渐变缓。     

Unsteady Elbow Pipe Flow to Develop a Flow-Induced Vibration Evaluation Methodology for Japan Sodium-Cooled Fast Reactor

This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in the Japan sodium-cooled fast reactor (JSFR), with particular emphasis on recent research and development activities that investigate unsteady elbow pipe flow. Experimental efforts have been made using 1/3-scale and 1/10-scale single-elbow test sections for the hot-leg pipe. The 1/10- scale experiment simulating the hot-leg pipe indicated no effect of pipe scale in comparison with the 1/3- scale experiment under inlet-rectified-flow conditions. The next experiment using the 1/3-scale test section was performed to investigate the effect of swirl flow at the inlet. Although the flow separation region was deflected at the downstream from the elbow, the experiment clarified a less significant effect of swirl flow on pressure fluctuation onto the pipe wall. An additional experiment was intended to study the effect of elbow curvature. The experiments with water revealed no clear flow separation in a larger curvature elbow case than that of the JSFR. Since the interference of multiple elbows should be investigated to understand turbulent flow in the cold-leg pipe geometry, 1/15-scale experiments with double elbows were carried out to clarify that flow in the first elbow influenced a flow separation behavior in the second elbow. Simulation activities include Unsteady Reynolds Averaged Navier Stokes equation (URANS) approach with a Reynolds stress model using a commercial computational fluid dynamics (CFD) code and Large Eddy Simulation (LES) approach using an in-house code. A hybrid approach that combined with RANS and LES was also applied using a CFD code. Several numerical results appear in this paper, focusing on its applicability to the hot-leg pipe experiments. These simulations reasonably agreed with the experimental data using the 1/3-scale test section.     

10MW高温气冷堆90°弯头内氦气流动特性分析

为了在10MW高温气冷堆中引入弯头传感器,通过实验和数值模拟的方法对90°弯头内流体的流动特性进行了研究,以实验获得的弯头内弧面和外弧面上的压力分布数据来对CFD模型计算的可信性进行评估,并应用验证后的CFD模型对高温气冷堆蒸汽发生器内90°弯头处氦气的流动特性进行数值模拟。通过对比实验数据和CFD模拟结果发现,实验结果与数值模拟结果基本趋于一致,90°弯头内、外弧面的压力呈现明显的不均匀分布现象,在弯曲角度α=30°~50°之间,内、外弧面的压力差达到最大值并持续保持一段位置,k-ω模型能用于预测10 MW高温气冷堆蒸汽发生器内90°弯头处氦气的流动特性。     

基于甲酸的硝酸亚铈微波脱硝前驱体的制备北大核心CSCD

以硝酸亚铈的硝酸溶液为原料,微波加热得到块状的固体产物,加入甲酸后继续加热可生成分散性良好的粉末状前驱体,通过X射线衍射分析(XRD)确定各步产物,并对煅烧前和煅烧后产物的粒度和形貌进行表征。结果表明,微波加热后得到块状的二水合硝酸亚铈,甲酸与其在加热条件下反应,生成棒状结构的甲酸铈。当甲酸浓度为16~20 mol/L、HCOOH/Ce摩尔比为18时,可得到粒度较为均匀的粉末。分别煅烧16 mol/L和20 mol/L甲酸制备得到的甲酸铈,煅烧后得到的二氧化铈与煅烧前的颗粒具有相同的形貌,粒径分布区间相似,但会生成一部分粒径小于0.30μm的细颗粒。     

Mechanistic multidimensional analysis of horizontal two-phase flows

The purpose of this paper is to discuss the results of analysis of two-phase flow in horizontal tubes. Two flow situations have been considered: gas/liquid flow in a long straight pipe, and similar flow conditions in a pipe with 90° elbow. The theoretical approach utilizes a multifield modeling concept. A complete three-dimensional two-phase flow model has been implemented in a state-of-the-art computational multiphase fluid dynamics (CMFD) computer code, NPHASE. The overall model has been tested parametrically. Also, the results of NPHASE simulations have been compared against experimental data for a pipe with 90° elbow.     

DEM-CFD simulation of modular PB-FHR core with two-grid method

For designing and optimizing the reactor core of modular pebble-bed fluoride salt-cooled high-temperature reactor (PB-FHR),it is of importance to simulate the coupled fluid and particle flow due to strong coolantpebble interactions.Computational fluid dynamics and discrete element method (DEM) coupling approach can be used to track particles individually while it requires a fluid cell being greater than the pebble diameter.However,the large size of pebbles makes the fluid grid too coarse to capture the complicated flow pattern.To solve this problem,a two-grid approach is proposed to calculate interphase momentum transfer between pebbles and coolant without the constraint on the shape and size of fluid meshes.The solid velocity,fluid velocity,fluid pressure and void fraction are mapped between hexahedral coarse particle grid and fine fluid grid.Then the total interphase force can be calculated independently to speed up computation.To evaluate suitability of this two-grid approach,the pressure drop and minimum fluidization velocity of a fluidized bed were predicted,and movements of the pebbles in complex flow field were studied experimentally and numerically.The spouting fluid through a central inlet pipe of a scaled visible PB-FHR core facility was set up to provide the complex flow field.Water was chosen as liquid to simulate the molten salt coolant,and polypropylene balls were used to simulate the pebble fuels.Results show that the pebble flow pattern captured from experiment agrees well with the simulation from two-grid approach,hence the applicability of the two-grid approach for the later PB-FHR core design.     

纳米级固体颗粒应用于热管的试验研究

对含有纳米级磁性微粒的磁性流体应用于热管进行了试验研究,分析了微粒浓度对热管传热性能的影响。试验结果表明．在试验研究的范围内,纳米级磁性颗粒应用于热管后减弱了热管的传热,而且磁性流体热管存在一个最优磁性微粒浓度,该浓度下磁性流体热管的传热性能最好。