Airflow in Automobiles

Measurement of Airflows in Automobile Ventilation Systems

Unique measuring technique

The measurement of airflow in automobile air-conditioning systems is under normal circumstances a thankless job, with the results obtained rarely measuring up to the effort expended. However, higher quality measurements with less effort can be obtained by changing to the tracer-gas measuring technique that has proved particularly well suited for measurements performed on compact air-conditioning and ventilation systems such as those in automobiles.

Reliable and accurate measurements

The following article presents the principles of the tracer-gas measurement method along with the techniques used to determine the different flows of a ventilation system. Examples are presented both of measurement of flow from the individual inlet vents and of the total flow under varying operating conditions. Several of the measurements have been performed as field tests, allowing for the determining of the influence of travelling speed on the ventilation systems.

Quick and easy measurements

The time required for tracer-gas measurements is quite moderate. Installation of the equipment takes approximately one hour, after which each flow measurement takes 10-15 minutes. The amount of tracer-gas required is quite modest, also. For the measurement illustrated 0.4 litres of SF6 was used, which is equivalent to 0.03% of the canister.

Instrumentation for air exchange measurements