THE IMPACT OF TRACER GAS MIXING ON AIRFLOW RATE MEASUREMENTS IN LARGE COMMERCIAL FAN SYSTEMS

摘要

We characterized the mixing of tracer gas in three fan systems under two airflow rate conditions. The systems were configured for 100% outside air and SF_6 gas was injected at a constant rate into the supply air stream. The tracer gas concentrations were measured using a GC/ECD. The downstream tracer gas mixing was evaluated by collecting samples from a 12 point sampling grid. Errors were calculated as the difference between the local and the average concentration divided by the average concentration. The maximum errors associated with central point sampling ranged from 0% to 14% and averaged 5.5%, while the errors associated with the 12 single point sampling locations ranged from 3% to 27% and averaged 11.2 %. Averaging of two sequential single samples did not significantly reduce errors. High and low flow rate data suggest that tracer gas mixing times of less than 6 seconds may result in higher errors.