应用微通道热泳脱除可吸入颗粒物的可行性研究

Study on feasibility of removing inhalable particle (PM_(2.5)) by using thermophoresis in microchannels

将热泳力和微通道流动两项国际前沿热门研究成果相结合.研究微通道内流动的可吸入颗粒物热泳沉积效率的变化规律.选择能描述有别于一般通道的具有强换热特性的微通道公式,计算分析其中换热特性和流动特性.通过在同样条件下一般通道与微通道内,利用热泳的效应,产生的脱除可吸入颗粒物效率的比较,得到在微通道内有大的热泳沉积效率的结论.这一结果给我们利用微通道内热泳脱除可吸入颗粒物以新的启发.通过多微通道组合可以实现高效率脱除可吸入颗粒物.若这一思路能够赋予实践,将为脱除细微的可吸入颗粒物的污染提供重大新途径.

The PM_(2.5) deposition efficiency by using thermophoresis in microchannels is studied. Some works on the thermophoretic deposition efficiency in ordinary channels have been done. The correlation suggested by Byers and Calvert is selected to calculate the thermophoretic deposition efficiency. Since the heat transfer in microchannels can be enhanced, the correlations for the calculation of the heat transfer in microchannels are different from those in ordinary channels. Choi S B.'s correlation is selected for the calculation of the heat transfer in laminar flow in microchannels. Xing Mingdao's correlation is selected for the calculation of the heat transfer in turbulent flow in microchannels. Sider-Tate's correlation is selected for the calculation of heat transfer in laminar flow in ordinary channels. Dittus-Boelter's correlation is selected for the calculation of heat transfer in turbulent flow in ordinary channels. Thermophoresis deposit efficiency of inhalable particles in microchannels is compared with that in channels with relatively large size at the same operating conditions. The calculated results indicate that the thermophoresis deposit efficiency of inhalable particles in ordinary channels is about 13.3%～14.8%, but the thermophoresis deposit efficiency of inhalable particles in microchannels is about 67.9%～72.1%, which is higher than in ordinary channels. The thermophoresis deposit efficiency of inhalable particles in microchannels increases from 24.0% to 81.9% with the inlet gas particle mixture temperature increasing from 50℃ to 300℃ when the tube wall temperature keeps 20℃. There are high the thermophoresis deposit efficiency of inhalable particles in microchannels for particle diameter between 1.5 and 3.0?μm.The calculated results also indicate that when the temperature difference between the gas-particle mixture and the tube wall does not vary, the deposition efficiency decreases slightly with the decreasing density, the increasing Pr, kinematic viscosity, specific heat and thermal conductivity of the gas for increasing the gas-particle mixture temperature. This study gives a new idea that inhalable particles can be removed by using thermophoresis in microchannels. The experiments are worth doing in future. If this method will work in practice, it may open an important and new way for removing inhalable particle (PM_(2.5)).