Fog formation study in non-ventilated aircraft cargo compartment

The high level of humidity within aircraft non-ventilated cargo compartment during shipment of perishables causes problems to the fire detection system. The goal of this research is to study the possibility of fog formation in cargo compartments. A test chamber capable of reproducing the conditions of pressure, relative humidity and temperature prevailing in a non-ventilated aircraft cargo compartment was built. A prediction model of these parameters was also achieved. Tests with no fog formation (40% relative humidity) were conducted for three depressurization airflows (0.19, 0.26 et 0.32 L/s). Another series of tests were completed for seven different relative humidities (13, 40, 50, 60, 70, 80 et 90%) with an airflow of 0.32 L/s. The initial temperature was set at 23.7°C for each test. The first series of tests showed the good behavior of the prediction model. Furthermore, the temperature drop was not influenced by the airflow. For the second series of tests, fog did form for tests at 80 and 90% relative humidity.