Gas sampling efficiencies and aerodynamic characteristics of a laboratory wind tunnel for odour measurement

Abstract

The rate of odour emission depends on meteorological factors, such as wind speed, humidity and temperature, but no wind tunnels control these factors adequately. A novel laboratory wind tunnel was developed that can control airflow rate. The gas recovery efficiency of the tunnel was evaluated and the aerodynamic characteristics were then examined to further assess its performance. Gas recovery efficiencies ranged from 62 to 107% with an average of 81%. The optimal performance of the tunnel (gas recovery efficiency of 89%) occurred at an airflow rate and CO supply rate of 1.68m3 min-1 and 10.0 l min-1, respectively. The vertical and cross-sectional wind speed profiles exhibited a substantial degree of non-uniformity. The airflow was turbulent, although Reynolds numbers were low indicating it to be close to laminar. The non-uniform wind speed profiles and CO concentration profiles illustrate the difficulty in obtaining representative samples from which to calculate emission rates. Further work is required to improve aerodynamic characteristics and hence performance of the tunnel.