Modeling particle deposition from fully developed turbulent flow in ventilation duct [An article from: Atmospheric Environment]

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Description:
This paper proposes an improved Eulerian model to predict particle deposition velocity in fully developed turbulent duct flow. The model is modified based on the three-layer model by Lai and Nazaroff (Journal of Aerosol Science, 31, 463-476, 2000), accounting for turbophoresis as well as Brownian diffusion, turbulent diffusion and gravitational settling. An expression relating the turbophoretic velocity to particle relaxation time, friction velocity and the normal distance to the wall surface is presented to model the turbophoresis. Similar with previous one by Lai and Nazaroff, the model only needs to input friction velocity, which makes it easy to apply. The predicted results agree well with measurement data for floor and vertical walls. And then deposition velocity of airborne particles to smooth walls in straight steel ducts is predicted by the modified model. The results agree with the published measured data, especially for floor and vertical walls of ventilation duct. Thus it is expected to be applied for predicting particle deposition in ventilation duct for indoor air quality control or evaluation. Furthermore, the condition to ignore turbophoresis for particle deposition is discussed by comparing the results of the improved model and that of Lai and Nazaroff.