| With the development of science and technology,economy and society,the demands of urban construction and the laying of municipal pipelines are gradually increasing,and the contradiction between their occupation of above ground space has gradually intensified.Developing and utilizing underground space rationally and planning and construction of pipeline can effectively solve this contradiction,so utility tunnel is gradually becoming one of the infrastructure of urban planning and construction.The research and application of utility tunnel in China is still in the early stage,some problems shall be solved urgently.After reviewing the literature,it is found when utility tunnel is operated normally,elimination of its waste heat is less studied.In this paper,ventilation mode of utility tunnel under normal condition is studied through combination of on site measurement and numerical simulation.The output of this paper may provide necessary theory and data reference for utility tunnel design.First of all,a lot of reliable data were obtained through on site measurement in power cabins in two utility tunnels in Suzhou,and they were sorted and analyzed.Data concludes air temperature,wall temperature and cable temperature of Tunnel A during some days in summer,and the same temperature of Tunnel B during all year.Secondly,a mathematical model was established based on the measured utility tunnel,and the reliability of the simplified geometric model,meshing,boundary condition setting and soil thermal performance parameters setting was verified by the measured data.Finally,the influence of pipeline heat dissipation intensity on natural ventilation and mechanical ventilation of utility tunnel is studied by using a validated mathematical model.The research conclusion can be summarized as follows:(1)When conducting unsteady numerical simulation of temperature field of underground structure or infrastructure,such as utility tunnel,the influence of surrounding soil water content and its variation with time on thermal properties of soil should be taken into comprehensive consideration.(2)Under natural ventilation conditions,The calculation method of maximum allowable heat dissipation intensity of pipeline under natural ventilation condition is determined.The estimated calculation method of air temperature and wall temperature in utility tunnel after stable operation is given.(4)Under mechanical year-round ventilation conditions,with the increase of heat dissipation intensity and air volume,the ratio of calculated air volume not considering soil heat transfer to simulated air volume decreases.The heat dissipation intensity could be regarded as the critical value when the ratio goes down to 1.When the heat dissipation intensity is less than the critical value,the actual required air volume is less than the calculated air volume.When the heat dissipation intensity is greater than the critical value,a certain air volume should be added to the calculated air volume which is not considering the soil heat transfer to ensure the safe operation of the utility tunnel. |
