Paper 6
A PQ-Formulation for Ventilation
Duct System Flow Analyses
Eero-Matti Salonen1 and Rauno Holopainen2
1 Helsinki University of Technology,
Department of Structural Engineering and Building Technology, PO Box 1100,
FIN-002015 HUT, Finland 2 Finnish Institute of Occupational
Health, Good Environmental Theme, Arinatie 3 A, FIN-00370 Helsinki,
Finland
Abstract
A formulation to analyze ventilation duct system airflows employing, as
the basic unknowns, the flow rates in the channel sections and the static
pressures at the channel section ends is presented. This approach is
called the PQ-formulation and the corresponding system equations are
called PQ-equations. The system equations in the PQ-formulation are the
engineering Bernoulli equations for the channel sections, the inlet and
outlet pressure jump equations at the inlet and outlet nodes, the
continuity equations at the junctions and the pressure jump equations at
the junctions. The nonlinear system equations are solved by the Picard
method using a relaxation factor. The linearizations employed in the
Picard method are described. Special additional themes are the treatment
of the updating of junction coefficients and the use of a so-called
balancing factor for checking convergence. Numerical demonstration results
are given in some example cases.
Key words: duct system flows, PQ-formulation, Picard method,
relaxation factor, balancing factor, junction coefficients, MATLAB
program.
References
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