Piston-wind ventilation strategy for thermal environment improvement of heat-supply compartment in utility tunnels

The thermal environment of the heat-supply compartment in utility tunnels is essential for the safe operation and easy maintenance of the pipeline system. Mechanical ventilation is usually employed to improve the thermal environment. However, the inevitable low outdoor air temperature in winter brings great difficulty to the mechanical ventilation effectiveness. This paper firstly performs a detailed simulation on the thermal environment in the heat-supply compartment under mechanical ventilation using the Fluent software. The results indicate that the air temperature in the first 50 m of a ventilation interval even falls below 0 °C under extreme conditions, hindering the pipeline operation and maintenance work. Therefore, a novel piston-wind ventilation strategy, which employs the piston-wind generated in a subway tunnel as the air source of ventilation, is proposed to solve the above problem. The piston-wind's applicability and superiority are validated through numerical comparison. The results demonstrate that the piston-wind ventilation exhibits higher suitability for the heat-supply compartment, since it creates superior temperature distribution than the mechanical ventilation. Further, the effect of vent size, piston-wind temperature, and piston-wind interval are simulated and discussed in detail. The results indicate that the larger vent size and the piston-wind interval between 2 and 4 min produce better ventilation effectiveness. The research finding is anticipated to provide an encouraging pathway for effective ventilation organization for the heat-supply compartment in utility tunnels.