Tunnel Ventilation

Using the constant tracer injection method one can measure the volume flow in a tunnel. As we can accurately measure down to the ppb and ppt-range only very small amounts of tracer gas are required.
As an example: An injection rate of just 10 ml/min is sufficient to measure a flow of 300.000 m³/h. The downstream concentration then will be 2 ppb.
Using multiple tracer gases more than one volume flow can be measured, e.g. for ventilation systems with exhaust one could measure the flow from the right and the flow from the left side.

 

 

Almost in all relevant questions in practice the tracer gas method is superior to the state-of-the-art flow measurement techniques in tunnel using pitot-traverses, averaging pitot tube, anemometers, ultra-sonic etc. Tracer gas tests can be done without any interference of the normal traffic. Also long term test are feasible without spending amounts of tracer gas.

The following questions can be quantitatively answered:

  • In tunnels with natural ventilation the influence of pressure differences on the airflow induced by traffic, temperature differences or meteorological changes between the portals
  • Measurement of short-circuiting between tunnel outlets
  • Measurement of local immissions of tunnel air in the vicinity of the portals
  • Validation of gas sensor placement for fan and damper control
  • Investigation of escape ways integrity
  • Validation of assumptions for ventilation system design
  • investigation of fume dispersal in case of fire
  • Simulation of special events and measurement of influence on ventilated air