In this paper, the possibility of reversed airflow was investigated.
There was a possibility of reversed airflow in a supply duct
system with one main duct and branches.
The possibility of reversed airflow was found to be eliminated
if the ventilation system is designed with a manifold. The main
fan maintains a positive pressure in the manifold. This prevents
reversed airflow. Theoretical and experimental investigations of
a manifold ventilation system with equal airflows in all branches
were performed where one fan was turned off to simulate a malfunctioning,
while the others stayed turned on. This did not result
in reversed airflow in the branch with the turned-off fan. The air-
flow in the branch was decreased while the airflow in the other
branches was increased.
It was found that there was a possibility of reversed airflow in
case the main fan malfunctioned. The main fan delivers the pressure
to maintain a positive pressure in the branch with the least
pressure and therefore also in the manifold. The pressure in the
branch with th