Dynamic Behavior of Aircraft Cabin and Air Conditioning System 2003-01-2397

During cruise flight, aircraft cabin environmental conditions are different from that found in a building. The relative humidity, mean radiant temperature and air density are lower than that found in a building environment. The relative humidity is around 15 to 20 %, the mean radiant temperature is lower than air temperature and the air density is lower than 1.18 kg/m³. The low relative humidity provides a higher evaporation and heat loss while the low mean radiant temperature imposes higher radiation heat loss. Besides, low air density implies a reduction of the convection heat loss due to lower heat transfer coefficients. The combination of these three factors requires different air temperature settings, compared to the ones usually applied in building environments.

In this paper, a comparison of two environmental control systems was considered. The first one was based on controlling the air conditioning system using the predicted mean vote (PMV) index as feedback signal, where the effects of air temperature, relative humidity, and mean radiant temperature were considered. The second used the cabin temperature as a feedback signal to the system.

The results showed that the combination of the effects of low relative humidity, low mean radiant temperature and low air density required higher cabin air temperature than that for building environments for thermal neutrality.