• Organisation

Today, the system design of tunnel ventilation systems including jet fans neglects the stream tube contraction being covered by the Rankine-Betz theory. 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 common but simplified design method by Meidinger dated back to 1964. 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. With the help of the new tool, tunnel design parameters (the number of jet fan units and the cross section ratio of jet fans and tunnel) and the operating conditions (velocity ratio of jet fan velocity and tunnel velocity) are predictable.