Extended Rankine-Betz Theory for Design of Tunnel Ventilation Systems

1.5 System & Preliminary Design

Today the system design of tunnel ventilation systems including jet fans neglects the stream tube contraction being covered by the Rankine-Betz theory. Thus, the presented system design tool extends in a truly physical manner the current method.
The influence of the stream tube contraction is discussed and compared to the design method. In addition, the traffic is treated as a peristaltic flow at high Reynolds number and friction losses are modeled with common approaches. The new model allows analysis of several extreme situations, like normal traffic flow, traffic jam and fire in a tunnel.
The results of the design tool are suitable velocity ratios of fan and tunnel as well as power consumption and operation condition.