A numerical method to determine the steady state distribution of passive contaminant in generic ventilation systems

Highlights ► A versatile numerical method to determine the contaminant distribution of ventilation system with recirculation at steady state is proposed based on typical ventilation systems with accessibility of supply air (ASA) and accessibility of contaminant source (ACS). ► The proposed method has comparable accuracy with the experiment and numerical simulation to predict the contaminant distribution in ventilation systems with recirculation at steady state. ► The proposed method is much more time-saving than numerical iteration method when a large amount of cases are needed to calculate. The lumped parameter model does not take the information of the source location and flow pattern into account, so it may cause large discrepancy with the real values. ► The advantages of the proposed method in terms of accuracy, speed and versatility make it possible to be widely applied for complex ventilation systems with recirculation.
Ventilation system with air recirculation is designed to conserve energy, yet at the same time may result in transporting hazardous substance among different rooms in the same building, which is a concern in indoor air quality control. There is a lack of effective methods to predict indoor contaminant distribution primarily because of uncertainty of the contaminant concentration in supply air which in turn due to the mixing ratio of fresh and recirculation air. In this paper, a versatile numerical method to determine the pollutant distribution of ventilation system with recirculation at steady state is proposed based on typical ventilation systems with accessibility of supply air (ASA) and accessibility of contaminant source (ACS). The relationship is established between contaminant concentrations of supply air and return air in a ventilated room or zone. The concentrations of supply air and contaminant distribution in each room can be determined using such parameters as ASA and ACS. The proposed method is validated by both experimental data and numerical simulation result. The computing speed of the proposed method is compared with the iteration method. The comparisons between the proposed method and the lumped parameter model are also conducted. The advantages of the proposed method in terms of accuracy, speed and versatility make it advantageous to be applied in air quality control of complex ventilation systems with recirculation.