Propagation of localized, unsteady heat loads in aircraft cabin air flows

Abstract

We studied experimentally the propagation of heat, released from a local source, in aircraft cabin air flow using two different ventilation systems. Besides the state-of-the-art mixing ventilation system, a ceiling-based cabin displacement ventilation system was employed. As test environment we used the Do 728 test facility of the German Aerospace Center in Gottingen. To measure the response of the cabin temperatures to the released heat, we evaluated the cross-correlation function between the local temperatures and the normalized surface temperature of the heat source. The latter was heated periodically at three different nominal heating powers, ranging from 100 W through 400 W. By analyzing the data, we could observe the gradual change of the temperature from a passive to an active scalar. While the two ventilation systems reveal a similar behavior at the lower source powers, the distinguished air-guiding principles of the momentum-driven mixing ventilation and the buoyancy-driven ceiling-based cabin displacement ventilation imply different propagation paths at higher power settings of the heat source. For the first time, the spatial spreading of locally released heat in mixing ventilation and in ceiling-based displacement ventilation was determined in an aircraft cabin.