O'Neill P J, Crawford R R
Bibliographic info:
10th AIVC Conference "Progress and trends in air infiltration and ventilation research" Espoo, Finland, 25-28 September 1989

This paper presents and evaluates a new method, based upon tracer gas techniques, for determining interzonal airflows and effective volumes in a multizone enclosure. Presently used tracer gas techniques have a number of drawbacks including the need for multiple tracers when analyzing a multizone structure. Also, traditional techniques cannot be used to independently determine flows and volumes in the multizone case. The method described in this paper eliminates some of the problems introduced by multiple tracers and allows the independent determination of both flows and volumes. The proposed method uses a single tracer gas to disturb the zones. A state-space formulation is used to model the multizone system. The concentration data are used in combination with a recursive least-squares identification algorithm to determine all of the interzonal airflows and effective volumes. A number of simulations are then used to validate the method The simulations show that there are important considerations to keep in mind when selecting the type of input applied to each zone. They also indicate that the proper choice of sampling interval is critical for accurate identification. The recursive least-squares formulation is readily adapted to the case where the system parameters are varying. A number of simulations show that this method can be used to track varying interzonal flows and effective volumes provided they are changing slowly with time. Finally, a method for determining the number of interconnected zones in a system is introduced. The method uses a single impulse applied to one of the zones. The tracer concentration in that zone is then monitored. The data are fit to an autoregressive moving-average model and the residuals are analyzed using Akaike's AIC criterion which provides an indication of the order of the system.