Well-Posed Models of Porous Buildings for Macroscopic Ventilation Analysis

Macroscopic methods of building ventilation analysis developed in the past fifty years have proven to be accurate and thus useful for purposes of single- and multi-zone building infiltration, air quality, smoke spread, thermal comfort, and integrated HVAC/building ventilation system analysis. These methods fail, however, to provide the same level of accuracy when applied to the analysis of wind-driven airflow through porous buildings. While it may be unreasonable to rely solely on macroscopic methods to model the complex three-dimensional phenomena associated with airflow through porous buildings, the accuracy of these methods may be improved if the analyst poses the airflow problem in a physically consistent and complete manner with the numerical consequences of the formulation in mind. This paper considers a number of strategies to achieve these objectives including: a) the coupled use of mass and mechanical energy conservation principles, b) the application of total pressure boundary conditions, c) the selection of appropriate loss coefficients for flow-limiting openings, d) corrections for non-normal wind directions, and e) the impact of system model topology, nonlinearity, and initial solution estimate on solution numerics.