Effect of ventilation on thermal and humidity environment of the underground utility tunnel in the plum rain season in southern China: Field measurement and CFD simulation

Abstract

The underground utility tunnel (UUT) is one of the typical urban underground structures, which usually requires mechanical ventilation systems for forced ventilation. In addition to the ventilation scheme for accident scenarios, the normal operating ventilation scheme deserves equal attention as it has a great impact on the air quality as well as the thermal and humidity environment inside the UUT. In this study, a UUT located in southern China is taken as the research object, and the effect of ventilation on its internal thermal and humidity distribution is explored with a combined use of field measurements and numerical simulations. The results of field measurements show that the average temperature inside the closed UUT is 20.5 ℃ and the average humidity ratio is 14.1 g/kgdry; both are lower than those of the external environment. In the plum rain season, if the tunnel is ventilated without any treatment of the external airflows, surface condensation tends to occur near the air inlet while the region with high relative humidity would be distributed on both sides far from the air inlet. The study also discusses the effect of different temperatures and humidity ratios of the inflow air on the humidity inside the UUT, and on this basis, the humidity control strategy for UUT in the plum rain season is proposed.