Role of Multi-Zone Models in Indoor Air Flow and Air Quality Analyses

Abstract

Multi-zone models generally take into account: mechanical ventilation, tight ness of buildings, and terrain, shielding and climate conditions. The output of these models include air flow rates across the envelopes, between the rooms and through the mechanical ventilation system. A multi-zone model is used to illustrate the potential of the multi-zone modelling in indoor air flow and air quality analyses. The model is applied to study the interaction between infil tration and mechanical ventilation, to develop simplified models for combin ing natural ventilation and exhaust ventilation, to understand smell transfer in a single family house, and to supply general flow boundary conditions in a computational fluid dynamics (CFD) prediction. Mechanical ventilation will change from the design data due to the changing of indoor pressure. To con sider the influence of infiltration, the quadrature and exponential superposi tion models give the best estimate of combined total flow rate. A change in the distribution of leakage or an opening can result in a different air flow rate and direction, and thus a different level of indoor air quality. By using the results from the multi-zone model as flow boundary conditions in a CFD code, an example calculation in a 13-room building shows that infiltration consider ably influences indoor air flow pattern.