Assessing airflow rates of a naturally ventilated test facility using a fast and simple algorithm supported by local air velocity measurements

摘要

The high spatial and temporal variations of airflow patterns in ventilation openings of naturally ventilated animal houses make it difficult to accurately measure the airflow rate:This paper focusses on the development of a fast assessment technique for the airflow rate of a naturally ventilated test facility through the combination of a linear algorithm and local air velocity measurements. This assessment technique was validated against detailed measurement results obtained by the measuring method of Van Overbeke et al. (2015) as a reference.The total air velocity vertical bar(U) over bar vertical bar, the normal vertical bar(Y) over bar vertical bar and tangential velocity component vertical bar(X) over bar vertical bar and the velocity vector vertical bar(U) over bar vertical bar measured at the meteomast were chosen as input variables for the linear algorithms. The airflow rates were split in a group where only uni-directional flows occurred at vent level (no opposite directions of vertical bar(Y) over bar vertical bar present in the airflow pattern of the opening), and a group where bi-directional flows occurred (the air goes simultaneously in and out of the opening). For airflow rates with uni-directional flows the input variables vertical bar(U) over bar vertical bar and vertical bar(Y) over bar vertical bar yielded the most accurate results. For this reason, it was suggested to use the vertical bar(Y) over bar vertical bar instead, of vertical bar(U) over bar vertical bar in ASHRAE's formula of Q = E x A x vertical bar(U) over bar vertical bar.For bi-directional flows a multiple linear model was suggested where input variable vertical bar(U) over bar vertical bar gave the best results to assess the airflow rate.