Ohba M, Irie K
Bibliographic info:
Sweden, Stockholm, KTH Building Services Engineering, 1998, proceedings of Roomvent 98: 6th International Conference on Air Distribution in Rooms, held June 14-17 1998 in Stockholm, Sweden, edited by Elisabeth Mundt and Tor-Goran Malmstrom, Volume 2

Air change rates in a cross-ventilation model were measured from the decay curves of video image signals obtained by the step down method assuming perfect mixing of tracer mists inside the spaces. Wind tunnel test results led to the following conclusions. 1) Ray extinction due to lighting scattering did not affect the measurement accuracy of the air change rates in the two-dimensional model. 2) Tracer mists in a diameter between 0.25 μ m and 2.0 μ m produced the same measurement accuracy. 3) With oil mists as a tracer, laser powers of more than 0.5 watts were enough to visualize the flow patterns in the model. 4) The air change rates were proportional to the reference velocities. 5) The proposed method measured the air change rates with an error of less than 9 %. This was the same accurate measurement as the tracer gas procedure using a high-speed hydrocarbon analyzer