BSL-3实验室不同通风方式下气溶胶颗粒分布的数值研究

目的：对BSL-3主实验室上送上排、上送下排2种通风方式的气流运动以及气溶胶颗粒浓度分布与排除进行数值研究。方法：利用离散轨道模型模拟气溶胶颗粒的轨迹,并与模拟气流运动的标准后叼湍流模型相耦合。结果：在主实验室送风量及压力不变的情况下。通风方式是影响气溶胶颗粒分布的关键因素。结论：上送上排案例方案对比上送下排案例方案有更多的颗粒逃逸、更少的颗粒悬浮与沉积以及更好的室内排污效率,上送下排案例方案对比上送上排案例方案在呼吸区以及整个室内有更小的颗粒平均浓度。     

BSL-3实验室内气溶胶扩散实验研究

本实验以烟雾模拟在BSL-3实验室内进行实验活动时产生的微生物气溶胶,以激光尘埃粒子计数器进行检测,研究BSL-3实验室内气溶胶扩散状况,为制定科学的防护和消毒措施提供依据。结果显示,在生物安全柜（BSC）内及其操作窗口外10cm以内的地方、负压罩内和实验室排风口中央位置释放的气溶胶,在实验室其他地方没有检测到;在实验室其他地方释放的气溶胶,可在实验室内不同的地方检测到。研究表明,在采用上送下排通风模式的BSL-3实验室内,一旦在BSC外出现溢洒或泄漏,所产生的微生物气溶胶可扩散到实验室其他地方而导致整个实验室被污染,需要立即采取措施进行控制。     

BSL-3实验室气流组织的数值模拟与实验研究

在动态的情况下，利用CFD软件，模拟了某BSL-3实验室内散流罩送风情况下的气流分布和污染颗粒的扩散情况；模拟和风口实测结果的吻合表明本次模拟有较好的可靠性，同时也证明在主实验室能够形成合理的定向气流．气流的运动状况是决定污染颗粒运动轨迹的主要因素。     

微生物检验车的研制

目的：研制一台主要开展病原体快速筛查检测工作的微生物检验车。方法：采用陕汽2190汽车底盘进行设计,将车厢划分为BSL-2＋实验间、缓冲间、送风空气处理设备间和排风净化设备间4个区域,进行紧凑合理科学的设备空间布局设置,满足移动实验室作业条件需求。采用全新风组合式空调处理系统以及上送下排、边侧送风、对侧排风的气流组织形式,形成由洁净区向污染区的定向气流,对实验室空气进行净化处理。结果：该检验车经试验测试．各项指标均达到设计要求。结论：微生物检验车可实现车厢内部的负压隔离,能够对周围环境形成有效防护和保证实验因子不受外界污染,为新发突发传染病防控提供快速、机动、安全、高效的检验平台。     

传染病员救护车病员室模拟气溶胶流动仿真与实验研究

介绍了装有负压净化装置的传染病员救护车的整体结构与功能设计。以CO2气体为模拟有害气溶胶污染物,运用两相流动模型计算其在救护车病员室内的流动特征与分布状态,并通过试验进行了验证。结果表明:救护车病员室内的CO2浓度分布与流场结构有利于细菌、病毒等气溶胶污染物通过负压净化装置排出病员室,影响气溶胶流动特征的主要因素是门窗缝隙的位置和密封程度。     

气溶胶粒子在呼吸系统内沉降规律的数值模拟

目的：研究可吸入气溶胶粒子在人体气管、支气管内的沉积规律。方法：建立基于Weibel模型的G0～G3级气管、支气管模型,在呼吸强度为15、30和60 L/min时,设定不同的出口边界条件,模拟气溶胶粒子不同密度和不同粒子直径时的颗粒沉积情况。结果：不同的边界条件下,流场变化不大,对粒子的沉积影响不大。相对于粒子密度,粒子的直径和呼吸强度对沉积规律的影响更大。结论：该研究对于开发新的气溶胶吸入治疗药物和新的气溶胶吸入治疗装置具有一定的借鉴意义,为进一步研究气溶胶浓度和失能剂起效的血药浓度的对应关系提供了一定的依据。     

负压二级生物安全实验室防护措施设计分析与评价

[目的]指导负压二级生物安全实验室防护措施设计。[方法]就负压二级实验室建造中的突出问题,结合工程实例,通过实验工艺、功能分区、平面布局、人流与物流组织、通风空调方式、气流组织、环境参数等关键因素分析,提出实施意见。[结果]应设缓冲间;核心间／动物间形态宜规整;宜设更衣和准备间。宜采用直流系统;整体气流由清洁区流向核心／动物间,核心,动物间气流由相对清洁．处流向污染源。气压梯度不小于10Pa;负压名义值：核心间,包括合并动物间的宜-20Pa;独立动物间宜-30Pa。[结论]设计不仅应符合生物安全理念和实验工艺要求,而且应符合暖通、建筑等原理与要求。该指导性意见对科学建设实验室具有积极意义,并已在许多工程中得以验证。     

BSL-3实验室内不同负压对定向气流影响的数值研究

目的：讨论BSL-3主实验室内不同负压状态对定向气流影响以及门缝渗风对气流的影响。方法：利用数值模拟与实验测试相结合方法进行研究。结果：在保证BSL-3实验室主实验室送风量不变的情况下,负压大小是影响实验室气流组织的关键因素。结论：在-50 Pa的状态下能形成较好的定向气流形式。     

水泥袋装车间粉尘控制模拟研究

目的分析并解决水泥包装车间粉尘危害治理问题。方法 2017年10月—2018年5月,以新疆某水泥生产企业袋装车间为研究对象,采用FLUENT数值模拟方法,对水泥厂包装车间现有通风条件粉尘扩散进行模拟研究。结果新疆某水泥生产企业袋装车间罩内通风系统设计不合理,造成包装车间和插袋工粉尘浓度超标分别为45.58、4.35倍(总粉尘)和20.68、2.87倍(呼吸性粉尘);在靠近尘源处、半密闭罩四角以及包装机后方风速较小,基本上在0.1～0.4 m/s,粉尘浓度较高,粉尘在呼吸带高度不同方位均存在不同程度的粉尘积聚;通过粉尘扩散模拟包装车间风流分布状况、粉尘扩散规律和通风控尘影响因素,袋装车间气流均匀性受通风设施风量、风口位置、风口大小等因素共同影响,通过不同方案组织优化模拟试验,最优方案插袋作业位置粉尘质量浓度在4～6 mg/m~3,较现有条件下粉尘质量浓度有明显下降,浓度在可接受范围内,气流组织最为合理。结论粉尘控制模拟研究达到水泥插袋岗位粉尘控制目的,有效解决了水泥包装车间粉尘危害这一问题,可为下一步开展水泥包装车间粉尘治理技术改造工作提供参考依据。     

传染性隔离病房的通风空调系统设计

本文介绍了传染性微粒的传播途径与特性;指出对于以飞沫和空气气溶胶方式传播的微生物,传染性隔离病房可以有效地控制污染源和切断传播途径;介绍了隔离病房通风空调系统设计方面的一些经验,包括空调系统、气流流向、房间气流组织、房间压力控制、换气次数、电气、自控、节能等方面的要求。由于我国隔离病房设计和施工的标准规范一直不健全,各个单位的做法也不一致,还有很多需要进一步研讨的地方,笔者希望与业内同行共商榷。     

Influence of room geometry and ventilation rate on airflow and aerosol dispersion: implications for worker protection.

Knowledge of dispersion rates and patterns of radioactive aerosols and gases through workrooms is critical for understanding human exposure and for developing strategies for worker protection. The dispersion within rooms can be influenced by complex interactions between numerous variables, but especially ventilation design and room furnishings. For this study, dependence of airflow and aerosol dispersion on workroom geometry (furnishings) and ventilation rate were studied in an experimental room that was designed to approximate a plutonium laboratory. Three different configurations of simulated gloveboxes and two ventilation rates (approximately 6 and 12 air exchanges per hour) were studied. A sonic anemometer was used to measure airflow parameters including all three components of air velocity vectors and turbulence intensity distributions at multiple locations and heights. Aerosol dispersion rates and patterns were measured by releasing aerosols multiple times from six different locations. Aerosol particle concentrations resolved in time and space were measured using 16 multiplexed laser particle counters. Comparisons were made of air velocities, turbulence, and aerosol transport across different ventilation rates and room configurations. A strong influence of ventilation rate on aerosol dispersion rates and air velocity was found, and changes in room geometry had significant effects on aerosol dispersion rates and patterns. These results are important with regards to constant evaluation of placement of air sampling equipment, benchmarking numerical models of room airflow, and design of ventilation and room layouts with consideration of worker safety.     

Observing and quantifying airflows in the infection control of aerosol- and airborne-transmitted diseases: an overview of approaches

With concerns about the potential for the aerosol and airborne transmission of infectious agents, particularly influenza, more attention is being focused on the effectiveness of infection control procedures to prevent hospital-acquired infections by this route. More recently a number of different techniques have been applied to examine the temporal-spatial information about the airflow patterns and the movement of related, suspended material within this air in a hospital setting. Closer collaboration with engineers has allowed clinical microbiologists, virologists and infection control teams to assess the effectiveness of hospital isolation and ventilation facilities. The characteristics of human respiratory activities have also been investigated using some familiar engineering techniques. Such studies aim to enhance the effectiveness of such preventive measures and have included experiments with human-like mannequins using various tracer gas/particle techniques, real human volunteers with real-time non-invasive Schlieren imaging, numerical modelling using computational fluid dynamics, and small scale physical analogues with water. This article outlines each of these techniques in a non-technical manner, suitable for a clinical readership without specialist airflow or engineering knowledge.     

Evaluation of leakage from a metal machining center using tracer gas methods: a case study

To evaluate the efficacy of engineering controls in reducing worker exposure to metalworking fluids, an evaluation of an enclosure for a machining center during face milling was performed. The enclosure was built around a vertical metal machining center with an attached ventilation system consisting of a 25-cm diameter duct, a fan, and an air-cleaning filter. The evaluation method included using sulfur hexafluoride (SF6) tracer gas to determine the ventilation system's flow rate and capture efficiency, a respirable aerosol monitor (RAM) to identify aerosol leak locations around the enclosure, and smoke tubes and a velometer to evaluate air movement around the outside of the enclosure. Results of the tracer gas evaluation indicated that the control system was approximately 98% efficient at capturing tracer gas released near the spindle of the machining center. This result was not significantly different from 100% efficiency (p = 0.2). The measured SF6 concentration when released directly into the duct had a relative standard deviation of 2.2%; whereas, when releasing SF6 at the spindle, the concentration had a significantly higher relative standard deviation of 7.8% (p = 0.016). This increased variability could be due to a cyclic leakage at a small gap between the upper and lower portion of the enclosure or due to cyclic stagnation. Leakage also was observed with smoke tubes, a velometer, and an aerosol photometer. The tool and fluid motion combined to induce a periodic airflow in and out of the enclosure. These results suggest that tracer gas methods could be used to evaluate enclosure efficiency. However, smoke tubes and aerosol instrumentation such as optical particle counters or aerosol photometers also need to be used to locate leakage from enclosures.     

厢式电梯通风方式对咳嗽飞沫核扩散的影响及风险分析

目的 在新型冠状病毒肺炎疫情背景下,探讨不同通风方式对轿厢式电梯内人员咳嗽飞沫核扩散的影响.方法 基于计算流体力学气固两相流原理,采用Realizable k-ε紊流模型和颗粒轨道模型研究轿厢式电梯内人员咳嗽产生的飞沫核在10 s内的扩散过程,比较三种电梯顶部送风(后部、两侧以及四角通风方式)下的气流速度变化、飞沫核扩...     

CFD investigation of room ventilation for improved operation of a downdraft table: novel concepts

We report a computational fluid dynamics (CFD) study of containment of airborne hazardous materials in a ventilated room containing a downdraft table. Specifically, we investigated the containment of hazardous airborne material obtainable under a range of ventilation configurations. The desirable ventilation configuration should ensure excellent containment of the hazardous material released from the workspace above the downdraft table. However, increased airflow raises operation costs, so the airflow should be as low as feasible without compromising containment. The airflow is modeled using Reynolds Averaged Navier Stokes equations with a high Reynolds number k-epsilon turbulence model. CFD predictions are examined for several ventilation configurations. Based on this study, we find that substantial improvements in containment are possible concurrent with reduction in airflow, compared with the existing design of ventilation configuration.     

An investigation of dust generation by free falling powders.

To identify the dust generation processes, aluminum oxide powder was dropped as a free falling slug in a test chamber. The effect of the slug's mass, diameter, and drop height upon the aerosol concentration and size distribution was measured with an aerodynamic particle sizer. To differentiate between aerosol generated during the free fall and at the end of the fall, the slug was dropped either onto a flat surface or into a container of water that suppressed dust generation associated with the impact at the end of the fall. Aerosol generation occurred during the slug's free fall as well as at the end of the fall. The falling solid induced an airflow that followed the falling solid to the end of the fall. This induced airflow contained the aerosol generated during the free fall. At the end of the free fall, the induced airflow, combined with air jets created on impact, dispersed the aerosol throughout the test chamber. Additional measurements were made by using "neutral buoyancy" helium-filled bubbles to visualize the airflow in the test chamber. The airflow and ensuing turbulence were sufficient to keep large, inspirable particles suspended throughout the test chamber for periods greater than 10 min. During experimental work, the effect of drop height, mass, and slug diameter upon aerosol generation by a single slug of powder was studied. The results indicated that the manner in which a powder is handled may be as important as material dustiness as measured by a dustiness tester. Aerosol generation can be reduced by minimizing the contact between the falling powder and the air.     

Development of a push-pull ventilation system to control solder fume.

Hand soldering using rosin core solder wire is common in the electronics industry and several studies have implicated the aerosol produced when rosin flux is heated in causing respiratory sensitisation. Control of solder fume is generally achieved using local exhaust hoods, simple blowers with a filter or low-volume high-velocity (LVHV) ventilation systems. None of these provide an ideal control system and so a push-pull ventilation design was developed as an alternative. Laboratory tests of the system's capture efficiency were carried out using nitrous oxide tracer gas. Capture efficiency was generally greater than 90% with the push airflow operating. However, without the push airflow, capture efficiency decreased sharply with increasing distance from the exhaust hood (between 38 and 58% at 420 mm from the front of the exhaust hood with the same exhaust airflow used by the push-pull system). The push-pull system was found to be relatively insensitive to obstructions placed in the path of the air flow or the influence of cross draughts.The system was tested in five electronics factories and the effectiveness was compared to their existing ventilation systems. Where only a small amount of soldering was carried out both the in-house and push-pull systems seemed to provide adequate control of inhalation exposure to rosin-based solder flux fume measured as total resin acids. However, the push-pull system provided more consistent control than the existing ventilation systems when larger quantities of solder were used. In these situations the mean personal exposure level was reduced to below the UK Maximum Exposure Limit (MEL) of 0.05 mg/m(3) 8-h time weighted average in most instances. The corresponding mean personal exposure level with the in-house systems in operation was about three to four times the long-term MEL. Interpretation of these data is complicated because of high background contribution to exposure from poorly controlled soldering operations elsewhere in the factories. However, this study suggests that the in-house systems were relatively inefficient.     

经排风系统传播SARS可能性的示踪气体实验研究

目的 测定和分析某医院住院部病房楼空气流向及其与排风管道分布的关系并探讨和验证严重急性呼吸综合征(SARS)在医院感染可能的传播途径和影响因素。方法 在某医院住院部SARS输入病例所在病房卫生间燃放植物油熏香(示踪气体);为控制病房卫生间排风扇的开启、顶层抽风机的状态和病房新风系统等主要影响因素,共设计了6种实验状态。由4组实验员分别盲法到各楼层的4、5号病房采集、测量空气样本,并分别按10等分记分法评估其气味浓度。结果 在医院住院部8～13层的各病房均检测到示踪气体,在不同实验状态下,气体弥散的方向和浓度不尽相同。结论 医院目前的建筑结构和通风系统具备了病原体气溶胶自下而上经排风管道垂直传播的通道和空气动力学条件,示踪气体的分布与发病分布有一定的关联性。提示SARS存在气溶胶或其他载体形式长距离传播的可能性和证据,而在现有设施条件下,针对性的预防管理措施可在一定程度上阻断病原体经排风系统的传播。