IGNITION BEHAVIOR OF HYGROSCOPIC MATERIALS IN HUMIDITY CONTROLLED ENVIRONMENT IN SMALL-SCALE TEST APPARATUS

摘要

The impact of equilibrium moisture content (4 to 12.5%) on piloted ignition times of hygroscopic material, such as corrugated paper cardboard samples has been measured over a range of incident radiant heat flux (up to 60 kW/m2) in the fire propagation apparatus (FPA – ASTM E 2058) under controlled humidity environment (20% to 90% RH). The variation of moisture content in corrugated cardboard is expected to have an effect on the ignition delay time as well as on the rate of fire growth. The results suggest that for a fixed radiant heat flux, the piloted ignition times increase by about 35% with the increase in moisture content from 4 to 12.5%. It has been concluded that, for incident radiant heat flux up to 60 kW/m2, the samples behave as a thermally thin materials. A simple thermally thin model is developed based on the energy required for ignition for a given net radiant heat flux delivered to the surface of the sample. This model predicts the time to piloted ignition for a given net heat flux, thermal properties and moisture content. Based on moisture dependent thermal property values obtained from the literature, the model has been extended to piloted ignition for thermally thick conditions.