Simulation study of dynamic air exchange rates in multizone environments in naturally ventilated residences
JIAN Yiwen1,2, GAI Xin1, FAN Chunmiao1, LIU Shuwei1
1. College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100124, China; 2. Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing 100124, China
Abstract：[Objective] Natural ventilation in real residential environments is characterized by dynamic multizone airflow. Ignoring either of the two features can lead to inaccurate assessments of natural ventilation in residences. The multiple tracer gas method has traditionally been used to investigate this multizone airflow within residential settings. However, it is impractical for large-scale applications owing to the high costs associated with the measurement process, potential disruption to occupants' daily lives, and the need for stable ventilation conditions. As a result, accurately measuring air exchange rates remains a significant challenge. A more in-depth study of the measurement method for dynamic multizone airflows is urgently required. This study proposes a simulation method for identifying dynamic multizone airflows in naturally ventilated residences. [Methods] This method utilizes CO2 emitted by occupants as a tracer gas to study multizone airflow in residential buildings. It considers all feasible multizone airflow patterns using a traversal approach and the air volume conservation principle. Furthermore, to strike an optimal balance between effectively tracking the dynamic characteristics of natural ventilation and minimizing noise sensitivity, a transient indoor CO2 mass balance equation associated with the Kalman filter is applied to each zone. The resulting time series of air exchange rates can be presented for each airflow pattern. These rates are then evaluated to identify the pattern that most closely aligns with the actual airflow pattern and the corresponding outdoor-indoor air exchange rates and interzonal airflow rates. Furthermore, two validation experiments were conducted in an unoccupied two-bedroom apartment with controllable ventilation patterns to validate the method. Subsequently, the method was employed in an occupied apartment, utilizing measured indoor CO2 concentrations and occupancy data for each zone to produce the time series of air exchange rates. [Results] The comparison among the calculated air exchange rates using the proposed method and experimental data indicates that 85% of the calculated values have absolute errors within ±0.2 h-1, and 95% fall within ±0.4 h-1. Furthermore, 75% of the calculated values have relative errors within ±10%, and 95% are within ±20%. The calculated air exchange rates and airflow directions closely match the experimental conditions, indicating that the method proposed in this study effectively represents the multizone aspects of natural ventilation in residential environments. Moreover, the applicability of the method to real residences is demonstrated through its application in an occupied apartment. The calculated air exchange rates for each zone during the measurement period, after filtering out anomalous results, fall within a reasonable range. These results present the airflow patterns that characterize the multizone nature of dynamic natural ventilation. [Conclusions] Natural ventilation is complex owing to its multizone nature and time dependence, leading to data scarcity. This method effectively addresses this gap by quantifying the multizone representation of dynamic airflows in residences on a large scale. Understanding indoor–outdoor air exchange rates and interzonal airflow rates is pivotal, as these parameters significantly influence indoor thermal conditions and air quality. In this regard, this study offers a valuable and practical approach to comprehensively understanding natural ventilation and its effects on occupants' health conditions in real residential environments.
简毅文, 盖鑫, 樊春苗, 刘书伟. 住宅多区域动态自然通风换气量的仿真研究[J]. 清华大学学报（自然科学版）, 2025, 65(5): 992-999.
JIAN Yiwen, GAI Xin, FAN Chunmiao, LIU Shuwei. Simulation study of dynamic air exchange rates in multizone environments in naturally ventilated residences. Journal of Tsinghua University(Science and Technology), 2025, 65(5): 992-999.
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2025, Vol. 65 
