Wang Lei, Wang Zhiqiang, Zhu Sirui, Zhu Zhe, Jin Tao, Wei Jianjian
Institute of Refrigeration and Cryogenics/Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou, China.
Center for Balance Architecture, Zhejiang University, Hangzhou, China.
Build Simul. 2023 May 11:1-13. doi: 10.1007/s12273-023-1023-3.
Intensive care units (ICUs) are the high incidence sites of hospital-acquired infections, where impinging jet ventilation (IJV) shows great potential. Thermal stratification of IJV and its effect on contaminants distribution were systematically investigated in this study. By changing the setting of heat source or the air change rates, the main driving force of supply airflow can be transformed between thermal buoyancy and inertial force, which can be quantitatively described by the dimensionless buoyant jet length scale (). For the investigated air change rates, namely 2 ACH to 12 ACH, varies between 0.20 and 2.80. The thermal buoyancy plays a dominant role in the movement of the horizontally exhaled airflow by the infector under low air change rate, where the temperature gradient is up to 2.45 °C/m. The flow center remains close to the breathing zone of the susceptible ahead, resulting into the highest exposure risk (6.6‰ for 10-µm particles). With higher heat flux of four PC monitors (from 0 W to 125.85 W for each monitor), the temperature gradient in ICU rises from 0.22 °C/m to 1.02 °C/m; however, the average normalized concentration of gaseous contaminants in the occupied zone is reduced from 0.81 to 0.37, because their thermal plumes are also able to carry containments around them to the ceiling-level readily. As the air change rate was increased to 8 ACH (), high momentum weakened the thermal stratification by reducing the temperature gradient to 0.37 °C/m and exhaled flow readily rose above the breathing zone; the intake fraction of susceptible patient located in front of the infector for 10-µm particles reduces to 0.8‰. This study proved the potential application of IJV in ICUs and provides theoretical guidance for its appropriate design.}.
重症监护病房（ICU）是医院获得性感染的高发场所，冲击射流通风（IJV）在其中显示出巨大潜力。本研究系统地研究了IJV的热分层及其对污染物分布的影响。通过改变热源设置或换气次数，送风气流的主要驱动力可在热浮力和惯性力之间转换，这可用无量纲浮力射流长度尺度（）进行定量描述。对于所研究的换气次数，即2次/小时至12次/小时，在0.20至2.80之间变化。在低换气次数下，热浮力在感染者水平呼出气流的运动中起主导作用，此时温度梯度高达2.45℃/m。气流中心保持靠近易感者前方的呼吸区，导致暴露风险最高（对于10μm颗粒为6.6‰）。随着四台电脑显示器较高的热通量（每台显示器从0W至125.85W），ICU内的温度梯度从0.22℃/m升至1.02℃/m；然而，占用区域内气态污染物的平均归一化浓度从0.81降至0.37，因为它们的热羽流也能够将周围的污染物轻松带到天花板高度。当换气次数增加到8次/小时（）时，高动量通过将温度梯度降低到0.37℃/m削弱了热分层，呼出气流很容易上升到呼吸区上方；位于感染者前方的易感患者对10μm颗粒的吸入分数降至0.8‰。本研究证明了IJV在ICU中的潜在应用，并为其合理设计提供了理论指导。
