Performance evaluation of alternative tunnel longitudinal ventilation systems using two inclined jets

摘要

This paper advances a novel design for providing longitudinal ventilation which utilizes the principle of induction while ensuring energy efficiency and allowing a better use of space. The induced longitudinal flow is generated by two inclined jets located about the midpoint between the floor and the ceiling allowing jets to entrain stagnant air freely necessary to guarantee the longitudinal air flux in tunnel. A mono-dimensional model and a CFD model have been developed in a parametric study to investigate the influence of inclination and the effect of confinement on the installation efficiency. It was found that by controlling the pitch angle of the two jets, the induction effect and then the installation efficiency are enhanced in order to achieve a successful use of the new ventilation system. Results show also that there exists an optimal confinement ratio assuring a better use of the longitudinal systems by producing the maximum induced air flow rate.