Coupled effects of the internal and external heat sources on flame spread behaviors over wires in a real building fire scenario

Abstract

Electrical fires are a major cause of building fires. In real fire scenarios, the combined effects of internal Joule heating and external radiation are crucial in determining flame spread and dripping behavior in electrical wires. To investigate wire flame behavior under the combined influence of internal and external heat sources, experiments were conducted using current generators and radiation panels. The results indicated that, under external radiation, the balance temperature increased proportionally to the square of the current, which led to an increase in flame spread rate and droplet frequency. External radiation also significantly accelerated the flame spread rate. When only internal Joule heating was applied, droplet mass was measured to develop a predictive model for droplet frequency, which was then validated by experimental data. External radiation increased both the length and flow rate of the flame, resulting in a significant decrease in wire flame height. It was found that radiation and current had nearly equal effects on flame spread and dripping behavior. As a result, wire flame behavior remained consistent, regardless of the heating direction. Understanding the interaction between internal and external heat sources is crucial for enhancing building fire safety and reducing the incidence of electrical fires.