Numerical simulation on ventilation and heat transfer of long-distance underground municipal tunnels across fire-prevention divisions

In view of the mismatch that the ventilation section of the comprehensive municipal tunnels is larger than the fire-protection section in engineering applications, the influence of the fire doors on the ventilation cooling in the underground municipal tunnel and the airflow movement law at the fire doors are studied. The CFD method is used to establish the numerical models of the municipal tunnel and the cable tunnel. The operating temperature changes along the length of the underground municipal tunnel during the three typical seasons (winter, summer, transition season) of the whole year are studied. It is concluded that the ventilation and heat transfer mode of the ventilation section across the fire-prevention division is feasible. In the summer condition without across the fire-prevention division, the municipal tunnel needs 4 h-1 air change rates to achieve the cooling effect, and the cable tunnel needs 6 h-1 air change rates. In the condition across the fire-prevention division, setting the fire door can strengthen the local heat transfer behind the fire door and reduce the air change rates.