THE IMPACT OF WALL HEATING ON LONGITUDINAL VENTILATION

When a downgrade tunnel is ventilated longitudinally, the increase of air temperature due to a fire has two main negative consequences: a loss of efficiency of the jet-fans and adverse buoyancy effects. To estimate air velocity, bulk air temperature therefore has to be computed precisely. In this paper, a simplified model is first described, showing the importance of taking into account wall heating. The code Camatt, which incorporates a finite volume formulation of the heat equation in the walls of tunnels, is then used. It shows that such a computer program should be used systematically when designing a ventilation system for a tunnel, at least as a verification, but preferably as early as the first definition calculations. (A)