Multizone Airflow Modeling in Buildings: History and Theory

Multizone airflow modeling has provided the means to predict building air-change rates and airflow patterns in buildings and their HVAC systems. Given reliable input data and application to circumstances consistent with the assumptions behind the models, these modeling tools are capable of providing valuable insights into a number of important building performance characteristics, including ventilation efficiency, energy consumption, indoor-air pollutant transport, and smoke control. Computer hardware and software developments over the past two decades have led to simulation techniques that may be applied to integrated buildings and HVAC systems of arbitrary scale and complexity to investigate both steady and dynamic transport phenomena in a fast and efficient manner. However, multizone modeling is only appropriate for investigating spatially averaged airflow rates; when transport details within rooms are needed, other simulation tools, such as computational fluid dynamics, are required. This paper reviews the historical development of the multizone airflow-modeling theory and outlines the current state of the theory, considering both the nodal and port-plane approaches to the formulation of the theory, and several analytic methods based on these approaches.