Performance evaluation of solar chimney in tunnel for passive ventilation and smoke exhaustion: A numerical approach

Solar chimney applied in building ventilation can passively regulate indoor air quality without electricity cost and carbon emissions, but its application in tunnel is limited. This study conducted a numerical modelling and theoretical analysis to investigate the volumetric flow rate through multi-channel solar chimney group in tunnel under normal and fire conditions. The influences of the solar chimney arrangements on ventilation and smoke exhaustion capacity were analyzed. Results show that the solar chimney group can afford natural ventilation in tunnel without compromising the performance of smoke exhaustion through shaft. With absorbed more solar energy, increasing cavity amount and cavity width can effectively improve the ventilation performance but limited effect on smoke exhaustion. The volumetric flow rate increases with cavity height and cavity depth that is proportional to hc1/3 and L2/3 under natural ventilation. The volumetric flow rate under natural ventilation and smoke exhaustion both increase with total chimney channel area. A theoretical model considering horizontally semi-parabolic temperature distribution inside each channel was developed to correlate the volumetric flow rate, the predictions agree reasonably with numerical results under normal and fire conditions. This study contributes to the application of solar chimney group in urban tunnels and guides extraction design.