Study On Protection Of Window Glass With Water Mist Curtain Under A Fire Scenario

Glass may break easily due to influence of excessive heat flux during a fire,leading to increase of ventilation in fire room and significant acceleration even cross-regional spread of enclosure fire.It is significant for fire prevention and control through studying how to prevent breaking and falling off of window glass.Thus,we adopt a window glass protection method to resist flame heat flux and decrease radiation received by glass in fire disaster by water mist curtain(WMC).The protective effect of WMC on window glass has been firstly studied under different operating pressures and different time of opening WMC.In addition,the protective effect of WMC and water film on float glass has also been compared.The results indicate that the time of window glass pane maintaining its integrated structure under the protection of WMC or water film extended.Under the installation condition of this paper,the results illustrate that the time of window glass pane maintaining its integrated structure under the protection of WMC or water film extends to more than 600 s comparing to that of 150 s without the protection of WMC and water film.The protective effect of WMC on float glass is better than water film with same flow rate.And as the pressure of water mistsystem increased,the protection efficiency of WMC improved.However,the protective effect of WMC is not obvious when work pressure is beyond 1 MPa.The effect of the time to open WMC or water film on thermal performance of glass was also investigated.It was found that the protection effect of separated WMC on window glass is not affected by delaying the activation of the WMC.However,delaying the activation of water film,the initial breakage time of window glass decreased.The protective effect of WMC on window glass has been firstly studied under different thickness of WMC.Several critical parameters,such as the first time of breakage occurrence,heat release rate,glass surface temperatures,temperature differences of window glass and loss of integrity of the glazing assembly,were recorded.The results show that the protective effect of WMC on window glass defers markedly when the thickness of WMC changes.And as the thickness of WMC increased,the protection efficiency of WMC improved,the time of window glass pane maintaining its integrated structure under the protection of WMC extended.Meanwhile,the total transmissivity and the attenuation factor of WMC with different thickness were calculated.The results indicate that the attenuation factor increases with the increase of the thickness of WMC.However,the attenuation factor of WMC is not obvious when thickness is beyond a critical value(the value is 7.5 cm in this paper).Based on the the attenuation factor of WMC,theoretical model for single glazing protected by WMC was developed to predict the breakage time of window glass.Comparisons between the predicted and experimental values have been conducted.It was found that the predicted results agree well with the experimental data.