On solution characteristics of coupling of multizone and CFD programs in building air distribution simulation

Multizone network models employ several assumptions, such as uniform pressure and quiescent air inside the zone, which may cause inaccurate results in flow calculations. This study intended to eliminate these assumptions in the zones, where these assumptions are inappropriate, by coupling a multizone network program with a CFD program. Through theoretical analysis, this paper proves that the solution of a building air distribution simulation by using the coupled program exists and is unique. Three possible coupling methods are then discussed and the best one is identified by studying their convergence and stability characteristics. A numerical test is further performed to verify the theory and it shows that the coupled program is able to effectively improve the accuracy of the results