Measurement of Air Flow Rate in a Naturally Ventilated Double Skin Facade

Air flow rate in a naturally ventilated space is extremely difficult to measure due to the stochastic nature of wind, and as a consequence non-uniform and dynamic flow conditions.

This paper describes three different methods to measure the air flow in a full-scale outdoor test facility with a naturally ventilated double skin façade. In the first method, the air flow in the cavity is estimated on the basis of six measured velocity profiles. The second method is represented by constant injection of tracer gas and in the third method a measured relation in the laboratory is used to estimate the flow rate on the basis of continues measurement of the pressure difference between the surface pressure at the opening and inside pressure of the double skin façade.

Although all three measurement methods are difficult to use under such dynamic air flow conditions, two of them show reasonable agreement and can be used for experimental validation of numerical models of natural ventilation air flow.