Measurement and modeling of spatial distribution of particulate matter in indoor environments.

摘要

A clear understanding of the particulate matter spatial distribution will provide useful information for improvement of ventilation system design and control strategies. In this study, a multi-point sampler was developed using critical venturi airflow devices to measure the dust mass spatial distributions in a typical swine building under production conditions and in a full-scale mechanically ventilated laboratory room under controlled conditions. The multi-point sampler is capable of sampling airborne contaminants at multiple points at the same time, and has been proven to be very accurate and reliable. Key results in this study are summarized in the following:;First, it was shown that the particle mass spatial concentrations vary widely within a mechanically ventilated airspace. Ventilation rate had a large effect on the particle spatial distribution. Increasing the ventilation rate reduced the overall mean particle concentration with the same ventilation system. At the same ventilation rate, the ventilation effectiveness varied widely with different ventilation systems.;Second, it was verified that the air outlet location had a substantial effect on the dust spatial distribution and the overall dust mass concentration. Comparison of ventilation effectiveness between two different ventilation systems showed that ventilation system design was critical to the dust control in a mechanically ventilated airspace. It was observed that there was a high dust concentration zone near the inlet side in a ventilated room with the air inlet in one sidewall and the air outlet in the opposite sidewall. Positioning the air outlet at the dustiest location can substantially improve dust removal effectiveness.;Third, it was shown that dust source control such as oil sprinkling at regular frequencies was an effective measure to control the dust levels. Room air cleaning such as dedusters can reduce the dust concentration and change dust spatial distribution.;Fourth, a 2-D mathematical model was developed based on the mass balance of particulate matter. The numerical simulation indicated that the particle spatial distribution was highly related to the airflow pattern, particle source strength and gravitational sedimentation of particles. The numerical simulations enhanced the understanding of the mechanisms of particle transport within a ventilated airspace.