Tunnels have very severe air quality constraints that typically require good ventilation system. The process of removing air from any space by mechanical means is known as evacuation. Evacuation of exhaust and smoke in case of fire emergencies is very necessary to bring in fresh air as it leads to pressure and temperature build up which causes discomfort to the passengers travelling especially in long tunnels. Generally, in longitudinal ventilation, a jet blower fan enclosed in a cylindrical casing is used for ventilation. These jet fans accelerate the air by imparting it an impulse in the desired direction. The main aim is to optimize the design and replace the jet blower fan cylindrical enclosure by a CD Nozzle. The suction fan along with rotor is exactly placed at the throat of the nozzle. The modeling is done using CATIA V5 software and CFD flow and modal analysis is carried out using ANSYS V 15.0. Various parameters like pressure, temperature, density, humidity and mass flow rate of air are measured and compared with the conventional model by experimentation and the results are validated.

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