Heat transfer enhancement effect of local ventilation inlong-distance utility tunnels

The ventilation and heat dissipation method of the existing utility tunnels is mainly the air exchange rate method. When the length of the utility tunnel increases, a very large amount of ventilation is required to meet the requirement that the temperature is not higher than 40 ℃ in the specification, the front end of the utility tunnel will be too cold, and the overall heat dissipation effect is not good. In this paper, a local ventilation method that can be used for long-distance utility tunnels is proposed, a numerical model of the local ventilation is established by CFD method, and its accuracy is verified by the scaled model experiment. The air distribution of local ventilation formed after the addition of jet fans is studied. The results show that the local thermal environment of the utility tunnel can be improved by setting the jet fan under the condition that the total air supply volume is the same, and the average temperature of the local section can be reduced by 0.5 ℃ under the working conditions studied in this paper. The comparative results show that the ratio between the inlet air volume of the utility tunnel and the air volume of the jet fan has little impact on the thermal environment in the utility tunnel. The jet angle of the jet fan has a significant impact on the optimization of the thermal environment in the utility tunnel, when the jet angle is 90°, the average temperature of the rear end section of the tunnel is reduced 0.41 ℃ and 0.33 ℃ compared with 0° and 45°, respectively, and 90° is the optimal jet angle.