Paper 9: Volume 5 No.1 June 2006 Edition
Well-Posed Models of Porous Buildings for Macroscopic
Ventilation Analysis
James
Axley and Daniel Chung
School
of
Architecture
,
Yale
University
,
New Haven
,
CT
,
USA
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.
Key words: multi-zone
building airflow analysis, porous buildings, discharge coefficient model,
power balance.
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