Ventilation Measurements

Measurements of combustion gases flows at the surface are necessary for calibration of the different dynamic and static models. In addition to the measurements of the summer field campaign 2004, GGA is planning to install a permanent pressure head measuring device in the near future.

Total gas flows through high and low temperature vents (T between 35°C and >400°C) as well as emissions from undisturbed soil covers have been measured.

The measurements have been performed by Stefan Schloemer for the BGR and, on behalf of DMT, by Jens Wiegand (University of Wuerzburg) and Tom Litschke (University of Essen).

It was planned to apply several methods to determine the gas flow, i.e. pressure head and flux chamber measurements, vane and heat wire anemometers,. However, it turned out that latter ones were only of restricted usefulness. In many cases the temperature was well exceeding the working range of vane and heat wire anemometers (i.e. T > 80°C) and often the ventilation zones were very small (less than a few centimeters) so that the instruments could not be positioned appropriately.

Pitot-static tubes (pressure head or dynamic pressure measurements) can be built of welded high-grade steel, therefore it is the airflow measurement system of choice for high temperatures (of up to 400 °C) that can be found in the cracks above the burning coal seams. For low temperature vents / cracks and for measurements of undisturbed soil flux chamber measurements have been applied.