摘要
医院内传染性呼吸道疾病患者通过喷嚏、咳嗽等剧烈的呼吸活动释放带致病菌的飞沫,如不加以控制,致病菌会通过空气传播导致医院传染。传染性隔离病房是控制传染源,切断空气传播途径的关键设施,本文从病房的气流组织和压差控制两个方面进行数值研究。
根据污染源的释放特性,建立有瞬态污染源和稳态污染源的病房模型。模拟一次性释放污染物的排除过程,比较换气次数、气流组织对该过程的影响。模拟稳态释放污染物的浓度分布,从气流组织、送风温度和采暖方式等方面比较,对气流组织进行优化。对不同气流组织下气态污染物和颗粒污染物的分布进行模拟,分析两种污染物分布差异及其原因。对病房气流组织的排污效率进行评价,考察气流组织和污染源的相互影响,在此基础上提出污染源指标,评价污染源对某位置的污染程度。
通过模拟计算,得到不同缝隙下渗透风量和通过缝隙压降之间的函数关系式,以及函数关系中流量系数和缝隙几何特性之间的关系。模拟计算病房开启状态下开门断面上气流速度的分布,为在开门断面形成定向气流,通过调节通风系统送、排风量增加通过开门断面流入病房的空气量,比较不同调节气流方式对形成定向气流的效果。采用动网格技术,主要采用二维简化病房模型,模拟不同开门方式(内开、外开或推拉)引起的流场、压力场变化。模拟病房内有污染物时,人员进入全过程污染物的扩散,评价不同开门方向对污染物扩散的影响。
在某部队传染性隔离病房进行一系列试验,以验证所采用的模型及相关参数的可靠性。模拟病房门关闭和全开启状态的流场、压力场,与实测值吻合较好。在病房内释放示踪气体CO2,稳定时测点的浓度和停止释放后浓度的衰减过程,测试值和模拟值吻合较好。用三维病房模型模拟门撤去后示踪气体的扩散,以及用二维简化模型模拟开门过程污染物的扩散,两者的结合和实测的前室浓度变化值吻合较好。
对病房气流组织和压差控制相关方面的研究结果,对隔离病房的通风方式的设计具有一定的指导意义。
The patient with infectious respiratory disease in hospital produces droplet-nucleiwith pathogens, if not under control, results in nosocomial infection by airbornetransmission. The infectious isolation room is necessary for controlling source andpreventing airborne transmission. This paper investigates the ventilation strategy andthe monitoring of room pressure with CFD.
The ward model of continuous or unsteady contamination sources wasestablished with specifying the contamination expelling characteristics. The removingpress of particles once released was simulated to compare the influence of differentventilation rate and air distribution. The steady distribution of particles was simulated,and optimizing analyses of the air distribution were carried by investigating the influ-ence of ventilation strategy, supply air temperature and heating mode. The differencebetween the concentration distribution of aseous or granular contamination wassimulated and the reasons to make this difference were analyzed. The ventilationsystems were evaluated with the ventilation efficiency. The local pollutantconcentration was decided by the air distribution and the location of contaminationsource, so the index of contamination source was defined to evaluate the localpollutant degree by the contaminant source.
The relationships between air infiltration flux through cracks under door andpressure difference and those between flux coefficient and geometry property wasobtained based on CFD. The velocity through the doorframe was obtained, and thebest way of adjusting flux of ventilation opening to obtain directional flow wasinvestigated. The field of velocity and pressure caused by different door swing (intoroom, out of room or along a wall) was simulated by dynamic mesh method. Theindoor contaminant diffusion in the press of people moving into room was simulatedand the influence of the direction of door swing on the airborne transfer ofcontamination was investigated.
Serious experiments was done in an isolation room was done to teat thevalidity of the model and related coefficient used in numerical simulation. Thesimulation results of velocity and pressure field under closed door or without door arein well agreement with measured values of velocity and pressure. The concentrationunder steady state when tracer gas CO2 releasing and the decaying press after it
stopped releasing are simulated, the value got by simulating and the measured valueof measuring points are close. The gas diffusion simulations with 3D model withoutdoor and with 2D simplified model with door swing are done respectively. Thecombined simulation results are closed to the change of concentration at themeasuring points in anteroom.The study results would administer to the design and assessment of the effectof air distribution and ventilation strategy in health care facility.
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