Experimental Study Of The Temperature Field In Air Ducts When Sediment Burning

With the development of the society and progress of the science and technology, heating and air-condition systems are used more and more in modern buildings. The ventilation and air-condition system of building supplies comfortable environment for work and life, however, because of the existence of sediment in ventilation ducts, air-condition system possibly become importance approach of fire spread and diffusion in buildings. At present, the influencing factors of fire and it's jeopardize are regarded importantly by correlative study organization in some countries, however, the influence of fire by sediment in ventilation and air-conditions system of buildings is referred rarely.The thesis analyzed influential factors of happening and spreading of fire which was brought by sediment in air-condition system, and investigated variation rule of temperature field when sediment burning. It analyzed influence of sediment on building fire. Experiment selected sawdust as a kind of sediment. It was conducted with sediment burning in rectangular ductwork, which approximate to ventilation ducts using real HVAC materials. These ducts were fabricated from galvanised steel. The scopes of the testing included temperature distribution in air duct under fire circumstance. Numerous thermocouples were installed at various cross sections and different measure dots within ventilation tube to measure temperature field.Results indicated that the factors such as air velocity and thickness of sediment had influence in speed of temperature distribution and length of hot smoke. Temperature variation in ducts had a sharp rise. Generally, after 2~10 minutes when sediment caught fire, temperature reached tiptop. Results indicated that the factors such as wind velocity and thickness of sediment and time of burning had influence in temperature maximum. When sediment burning, temperature grads along duct and maxima of temperature could not appear simultaneously. Downward grads of tip surface temperature were smaller than underside temperature in air ducts.Otherwise, this thesis used uniformity design to design experiment and utilized multiple linear regression analysis to acquire relation of every fact and temperature. Finally, some measures including design, maintence and management of the systems need to be taken in order to reduce the probability that the sediment became source of fire and pipeline of fire spreading in a building. Thesis afforded referrence for establishing the criterion on analysis of fire cause and fire's prevention.