Occupiable areas within the vicinity of tunnel portals, for example residential buildings, office buildings etc... require proper air management to reduce or eliminate portal emissions. Traditionally fan stations upstream tunnel exits consists of large axial fans to extract polluted tunnel air to the atmosphere. The recently opened E4/E20 motorway tunnel: The Northern Link Tunnel in Stockholm, Sweden, employs a new fan station concept which is based on the principle of using jet fans. This paper describes the design behind this type of fan station, the follow up with flow measurements, CFD simulations in the design phase and on as-built constructions, lift cycle cost analysis and benefits achieved from employing such a design as well as functionality and operability.
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