Quantitative effects of supply air and contaminant sources on steady contaminant distribution in ventilated space with air recirculation

Abstract

Identifying the contributions of different influencing factors to indoor air environment is beneficial for seeking measures to improve environmental quality. The independent effect of supply air and contaminant source can be quantified using accessibility index; however, for ventilated rooms with air recirculation devices, the effects of supply air and contaminant source cannot be described directly owing to the effect of air recirculation. In this study, a concise linear expression is derived to establish a correlation between steady contaminant distribution and each of independent supply air and contaminant sources with air recirculation, based on which index of revised accessibility is defined to evaluate the effects of supply air and contaminant sources. The reliability of the proposed method is verified by comparing with simulation result. Two numerical cases, i.e., two air recirculation devices with cleaning efficiency and a recirculated air curtain, are analyzed to study the quantitative effects of supply air and contaminant source. It is discovered that air recirculation devices change the airflow field considerably, and that the purification effect of air recirculation devices with cleaning efficiencies of 0.2 and 0.3 reduces the effects of supply air and contaminant source. The recirculated air curtain reduces the dominant area of air supply inlet, with regional revised accessibility decreasing from 0.69 to 0.54. Air curtain at an appropriate airflow rate significantly reduces the effect of contaminant source at distant areas, with regional revised accessibility decreasing from 1.03 to 0.64. The proposed method is beneficial for evaluating air recirculation in establishing indoor environment.