Well-Posed Models of Porous Buildings for Macroscopic Ventilation Analysis>

Abstract

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.