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首页> 外文期刊>Heat Transfer Research >WATER VAPOR CONDENSATION ON THE INNER SURFACE OF AN N95 FILTERING FACEPIECE RESPIRATOR
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WATER VAPOR CONDENSATION ON THE INNER SURFACE OF AN N95 FILTERING FACEPIECE RESPIRATOR

机译：N95过滤面板呼吸器内表面上的水蒸气凝结

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摘要

N95 filtering facepiece respirators (FFRs) are commonly used in China to reduce the inhalation of hazardous air pollutants, especially in industrial cities with elevated PM2.5 concentrations. 1195 FFRs block at least 95% of particles, but the breath increases the relative humidity in the dead space, which can make the wearer uncomfortable. Furthermore, water vapor condensation, combined with an appropriate temperature and humidity inside the respirator, creates a favorable environment for bacterial growth and reproduction, which presents another health hazard. However, direct and real-time observation of water inside the dead space of an FFR is difficult, since water volatilizes quickly once the FFR is removed from the wearer's head. The objective of this research is to study the distribution characteristics of water vapor condensation on the inner surface of an FFR under different breathing conditions, including different environmental temperatures and breathing patterns. We used the computational fluid dynamics (CI-D) method to simulate the flow-field in the upper respiratory system of a user wearing an N95 FFR. We analyzed the distribution of temperature, water vapor, and liquid water volume fraction on the inner surface of the FFR at various environmental temperatures. We also noted the variations of these factors when a sudden drop in environmental temperature occurred. Different breathing rates and frequencies were also investigated. When the environmental temperatures were 370.75 K, 296.6 K, and 273.15 K, the temperatures inside the FIR were 309.13 K, 302.55 K, and 291.03 K, respectively. Sudden drops in the environmental temperature from 296.60 K to 273.15 K and from 310.15 K to 273.15 K can increase the volume fractions of liquid water by 20.03% and 21.07%, respectively. Compared to the typical breathing rate v(0)(t), when the breathing rates increased to 2v(0)(t) and 3v(0)(t), the maximum temperatures increased from 301.72 K to 303.02 K and 303.54 K, and the maximum fractions of liquid water decreased by 12.98% and 22.33%, respectively. When the breathing frequency was changed, the variation of the maximum temperatures was less than 1 K, and the maximum fractions of liquid water decreased by 40.08% at half the normal frequency and increased by 83.97% at double the normal frequency. The presence of liquid water can aid bacteria reproduction, which may be a health hazard to the wearer.
机译：N95过滤面板呼吸器（FFR）通常在中国使用，以减少危险空气污染物的吸入，特别是在工业城市，浓度升高。 1 195 FFR阻止至少95％的颗粒，但呼吸增加了死区中的相对湿度，这可以使佩戴者不舒服。此外，水蒸气缩合，结合呼吸器内部的适当温度和湿度，为细菌生长和繁殖产生了有利的环境，这提出了另一种健康危害。然而，难以直接和实时观察FFR的死区内的水域是困难的，因为一旦从佩戴者的头部移除FFR，水就会快速挥发。本研究的目的是研究在不同呼吸条件下的FFR内表面上的水蒸气凝结的分布特性，包括不同的环境温度和呼吸模式。我们使用了计算流体动力学（CI-D）方法来模拟佩戴N95 FFR的用户的上呼吸系统中的流场。我们分析了各种环境温度的FFR内表面上的温度，水蒸气和液体水体积分数的分布。我们还注意到当环境温度突然下降时，这些因素的变化。还研究了不同的呼吸率和频率。当环境温度为370.75 k，296.6k和273.15 k时，杉木内的温度分别为309.13k，302.55 k和291.03 k。环境温度下的突然下降到296.60 k至273.15 k和310.15 k至273.15k可以分别将液态水的体积分别增加20.03％和21.07％。与典型的呼吸速率V（0）（t）相比，当呼吸率增加到2V（0）（t）和3V（0）（t）时，最大温度从301.72k增加到303.02 k和303.54 k，液体水的最大馏分分别降低了12.98％和22.33％。当呼吸频率改变时，最大温度的变化小于1 k，液态水的最大馏分在正常频率的一半下降40.08％，并且在正常频率下增加了83.97％。液体水的存在可以帮助细菌繁殖，这可能对穿着者的健康危害。

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