Research And Analysis Of Model And Mechanism Of Heat Transfer Within Fire Extinguishing Foam

Foam fire-fighting agent is an important approach to deal with fire accidents,its extinguishing ability relates closely with the safety of life and possession,therefore it's of major importance to conduct a research on the extinguishing ability of foam agent.Recent years extensive literature about experimental work on the ability of foam agent has been report,the experiment subjects include gas-liquid two phase foam and gas-liquid-solid three phase foam,and the experiment contents embody foamability,liquidity,static stability,thermal stability and heat-shielding ability.However,numerical models about heat transfer within fire-fighting foam are rarely seen.At the beginning of this article,the classification and research progress of fire-fighting foam agent are summarized.Then the research ideas aiming at solid closed-cell foam are introduced into the consideration of heat transfer process within gas-liquid two phase foam,meanwhile the influence of evaporation,foam expansion are also taken into account,and the convective contribution inside the tiny foam cells is ignored.With the help of Stefan boundary condition,the evaporation problem is turned into an geometric problem with a moving boundary,consequently the conduction-radiation-evaporation heat transfer model of gas-liquid two phase foam is put forward.Afterwards,on the basis of two phase foam heat transfer model,nanoparticle dispersion's influence on the thermal parameters and heat transfer mechanism of the foam layer is considered,thus the two phase model is expanded to gas-liquid-solid three phase foam model.The research results show: the thermal stability and heat-shielding performance of the two kinds of foam layers both decrease as initial gas volume percentage and top temperature increase,however the initial height of the two foam layer has nothing to do with thermal stability;As for the three phase foam,more nanoparticle content and smaller nanoparticle diameter contribute positively to the improvement of thermal stability and heat-shielding performance.