Tunnel and Enclosed Space Ventilation Duty
Tunnel, car park and shaft ventilation: reversible and emergency duty, corrosion protection and the axial decision.
The duty
Low pressure, high volume, and it must work in an emergency
Ventilation of an enclosed space is dominated by volume rather than pressure: the air has to move a long way with as little head as the civil works will allow. Below roughly 50 mmWC an axial machine is usually the efficient answer; above it, or where the duct is short and dirty, a centrifugal exhauster takes over. Our own range documentation draws exactly that line between axial fans and centrifugal blowers.
The difference between a ventilation fan and a tunnel fan is what happens when it is called into emergency mode. Reversal, second-speed start, fire-rated insulation on cable, corrosion protection against a damp underground atmosphere and a control interface that survives a power change-over are all specified before the machine is built, not discussed afterwards.
Noise and the boundary
Fan noise scales with about the fifth power of tip speed, so a larger wheel run slower is often the only way to meet a boundary limit at a portal or a street-level grille.
Data we need
Ventilation data for a selection
Tunnel and shaft data
- Volume per cell, per shaft or per portal in CMH
- Available total pressure, from the ventilation study
- Normal, boost and emergency duty modes and the change-over time
- Whether reversal is required, and in which direction
- Air temperature in fire mode and for how long
- Corrosivity: damp, saline, grime or chemical exposure
- Mounting: inline, shaft, portal or plant room
- Control interface, starter type and the applicable standard
Next step
Fans for this duty
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