An analytical model of stack ventilation in a shaft with controllable air volume

Abstract

This work investigates a stack ventilation system in a shaft with controllable air volume suitable for large public buildings, which can adjust natural ventilation volume on demand and avoid heat loss in winter. The driving force and resistance of this system was analysed, a correction coefficient C0 for air confluence in the shaft was proposed based on the local resistance of a confluent T-junction, and a quantitative model of ventilation volume and height of a neutral plane was developed. Then, the inlet air volume obtained from field tests of the shaft in an actual project during the autumn, as well as the driving temperature obtained from computational fluid dynamics (CFD) simulations of the airflow in the shaft (using the test results as the boundary conditions), were used to solve for C0. Finally, the model was validated by the comparison of predictions with the inlet air volume obtained from tests of the shaft in the same project during the winter and heights of the neutral plane from the simulations. The results showed that this model was reasonably accurate and suitable for the design of stack ventilation systems in shafts for large public buildings with controllable air volume.