An analytical study of branched connections: its implications to multizone air flow measurements.

A branched connection is a single air flow passage connecting more than two zones. Its existence in a building has not been a critical issue for the measurement of air flows of single zones, as far as the validity or accuracy of the measurement techniques is concerned. However, with the ever increasing sophistication of building air flow measurement techniques --- which include tracer gas and multifan pressurisation techniques --- and the ever increasing use of them in multizones, it becomes increasingly desirable to examine the effect of branched connections. This paper presents an analytical study of the validity of the multizone air flow measurement techniques, as they are applied to buildings containing branched connections. It is found that the multifan pressurisation techniques have embedded inadequacies, which could lead to large flow rate measurement errors, if the techniques are applied to buildings containing branched connections. It is also found that all tracer gas techniques are valid regardless of the types of connections present. However, the interpretation of their results is much more restricted than in the case where only direct connections exist in the tested building,