Network Flow Modelling for Optimizing Fire Smoke Control in Complex Urban Traffic Link Tunnels: Incorporating Heat Loss and Gas Species Generation Rate Calculation into Models

Abstract

We propose the use of network flow analysis for designing and optimizing the smoke control in urban traffic link tunnels (UTLT) with multiple branches. Up-to-date, there have been no specified codes and standards for the application of conventional smoke control measures, such as jet-fan induced longitudinal ventilation and centralized smoke extraction using axial fans, in such tunnels. The use of network flow analysis could avoid the huge computational cost in large and complex tunnels. A self-developed network code incorporated with basic conservation equations was employed in a practical UTLT. The simplification algorithms for calculating the heat transfer rate at the tunnel envelopes and the gas species generation around the fire source were newly presented in this paper. The network analysis results are compared against a three-dimensional numerical simulation, and good agreements were obtained between them. Then, a hybrid mode including a combination of longitudinal ventilation and centralized extraction was simulated using the network code. The benefits and applicability were discussed.