Balocco Carla
Department of Energy Engineering "Sergio Stecco", via S. Marta 3, 50139 Firenze, Italy.
Build Simul. 2011;4(1):5-20. doi: 10.1007/s12273-011-0019-6. Epub 2011 Dec 4.
Airflow and ventilation are particularly important in healthcare rooms for controlling thermo-hygrometric conditions, providing anaesthetic gas removal, diluting airborne bacterial contamination and minimizing bacteria transfer airborne. An actual hospitalization room was the investigate case study. Transient simulations with computational fluid dynamics (CFD), based on the finite element method (FEM) were performed to investigate the efficiency of the existing heating, ventilation and air-conditioning (HVAC) plant with a variable air volume (VAV) primary air system. Solid modelling of the room, taking into account thermo-physical properties of building materials, architectural features (e.g., window and wall orientation) and furnishing (e.g., beds, tables and lamps) arrangement of the room, inlet turbulence high induction air diffuser, the return air diffusers and two patients lying on two parallel beds was carried out. Multiphysics modelling was used: a thermo-fluidynamic model (convection-conduction and incompressible Navier-Stokes) was combined with a convection-diffusion model. Three 3D models were elaborated considering different conditions/events of the patients (i.e., the first was considered coughing and/or the second breathing). A particle tracing and diffusion model, connected to cough events, was developed to simulate the dispersal of bacteria-carrying droplets in the isolation room equipped with the existing ventilation system. An analysis of the region of droplet fallout and the dilution time of bacteria diffusion of coughed gas in the isolation room was performed. The analysis of transient simulation results concerning particle path and distance, and then particle tracing combined with their concentration, provided evidence of the formation of zones that should be checked by microclimatic and contaminant control. The present study highlights the fact that the CFD-FEM application is useful for understanding the efficiency, adequacy and reliability of the ventilation system, but also provides important suggestions for controlling air quality, patients' comfort and energy consumption in a hospital.
气流和通风在医疗保健房间中对于控制温湿度条件、去除麻醉气体、稀释空气中的细菌污染以及最大限度减少空气传播的细菌转移尤为重要。一个实际的住院病房是研究案例。基于有限元法（FEM），采用计算流体动力学（CFD）进行瞬态模拟，以研究现有带变风量（VAV）一次风系统的供暖、通风和空调（HVAC）设备的效率。对房间进行实体建模，考虑了建筑材料的热物理特性、建筑特征（如窗户和墙壁朝向）以及房间的家具布置（如床、桌子和灯具）、入口湍流高诱导空气扩散器、回风扩散器以及两名躺在两张平行床上的患者。采用多物理场建模：将热流体动力学模型（对流 - 传导和不可压缩纳维 - 斯托克斯方程）与对流扩散模型相结合。考虑患者的不同状况/事件（即第一个患者被认为在咳嗽和/或第二个患者在呼吸），精心构建了三个三维模型。开发了一个与咳嗽事件相关的粒子追踪和扩散模型，以模拟配备现有通风系统的隔离病房中携带细菌的飞沫的扩散。对隔离病房中飞沫沉降区域以及咳嗽气体中细菌扩散的稀释时间进行了分析。对关于粒子路径和距离的瞬态模拟结果进行分析，然后将粒子追踪与其浓度相结合，提供了应通过微气候和污染物控制进行检查的区域形成的证据。本研究强调了CFD - FEM应用对于理解通风系统的效率、充足性和可靠性很有用，而且还为控制医院空气质量、患者舒适度和能源消耗提供了重要建议。
