Simulation results of a subway environment ventilation using a developed code “SSES”

washers, fans and other devices may be required. This kind of setup is typically a requisite for the warm air in the summer to create a comfortable environment for the passengers. The last type of ventilation is in the case of an emergency, like the times the train is caught in fire. This kind of situation requires larger amounts of ventilation, which needs to be provided by mechanical means. For a further discussion on these cases, one may consult the subway environmental design handbook [1]. In this article, our main concern is about the piston action of the train and the natural ventilation of the subway environment in normal operating conditions. In our model for the piston action, we only consider the one-dimensional changes along the subway track. This is in contrast to the costly 2D and 3D simulations by the commercial software, e.g. Fluent. Such a 1D simulation, although less accurate, can give results which are physically acceptable and a primitive design may be based on them. The velocity and pressure profiles in a coordinate system traveling with the train and a fixed coordinate at the stations are derived and shown to be true, physically. The second important part of the article is about the section added to the code so that by considering parameters of the patron, train and station data, the code calculates the total heat gain production and the required ventilation can be calculated. The ventilation fluxes are given for each of the channels in a single station. So this amount of ventilation, along with the natural ventilation effect of the piston action of the train may be used as design criteria of the subway ventilation system. Also the effect of the various parameters on the ventilation can be investigated. Formerly, some codes have been developed for such calculations. The most eminent software in this field is the SES software (Subway Environmental Simulation) [1], designed by the U.S. department of transportation. This code has been used before for the design of some subway systems around the world and can calculate ventilation parameters for natural, forced and emergency ventilation occasions. Also some articles are published about the designs which have been carried out, using this specific code [2]. The current code provides some of the data generating mechanisms of that software, but it is designed for the natural and mechanical (and not emergency) ventilations only. This code is used in the design and simulation of the ventilating systems of 5 stations of a track in the Tehran subway system. The installation of the ventilation equipment system of one of the stations has been completed and it is now under public use. Abstract The piston action of a moving train in an underground subway can act as a ventilator of the subway environment. The modeling and simulation of this type of ventilation, provides a means to investigate the natural ventilation of the system and to ensure that the pressure changes doesn’t bother the passengers. A visual Basic GUI code has been developed to calculate the velocity and pressure distributions that may be generated due to the natural ventilation, caused by the piston action of a moving train. The outcome of the software includes the Lagrangian and Eulerian velocity and pressure profiles along the track. The other results is the heat flux generated due to different mechanisms like the train braking, car accessories, lighting and etc. These data are used in the code to calculate the required forced ventilation (without considering the natural ventilation). Using the heat generation data, one can design the subway equipments and incorporating natural ventilation outputs, the comfort criteria can be evaluated. The code is used to simulate a subway track in Tehran and the results are in a very good agreement with the physical anticipations. The track includes 5 stations in its way, namely Enghelab, Valiasr, Ferdowsi, Darvaze Shemran and Shohada, for which we have done a heat generation analysis and calculated the required mechanical ventilation. The code is developed by the cooperation and team work of the “Sharif Subway Environmental Design Team” (SSEDT). Accuracy verification and realization of the code's capabilities, eases the future work of the team, that may be conducted for the other lines of the Tehran subway system.