To prevent spread of a fire, the glass that has fire prevention performance has to be used in windows of fire proof walls. The glass called
fire glass is generally used for that, and now fire glass panes have been used very much. On the other hand, from the point of view of energy saving, windows tend to be the weak point in the daily life, and the glass of which high heat insulation and the solar shading effect of the Low emissivity (Low-E) Insulated Glass Unit (IGU) is widely used. Although Low-E glass is used to shade solar radiation heat of infrared wavelength domain, the effect can also be shown to the radiant heat by fire as well as sunshine. Now many Japanese window-manufacturers acquire the certifications as the Low-E IGU combined with wired glass or heat-resistant tempered glass for house windows. If it would be possible to reduce the radiant heat flux of fire, Low-E glass can be expected as glass for prevention of fire spread from windows in a crowd uptown.
Therefore the purpose of this study was to clarify fire prevention performance of the Low-E glass on fire by checking the breakage of glass and the radiant heat reduction effect.
The fire test condition is shown below.
·Fire tests were performed for Low-E coating single glass pane coated one side, and each Low-E glass pane was heated with the both sides along the ISO834 Heat Curve for each specimen. (Figure3)
·The temperature of the glass was measured by thermocouples and ΔT was defined as the temperature difference of the center of glass and the edge of glass. The radiant heat flux was measured 1.0m away from glass surface by a heat flux gauge. (Figure4)
·In these fire tests, Low-E coating glass panes of emissivity value 0.05±0.02 , 0.15±0.02 and no coating glass panes were used.
Findings are as follows.
1) Figure8 and Table 3 shows that when Low-E coating glass is heated on coating side, temperature difference(
ΔT) decreases by the radiant heat reduction effect of the Low-E coating. Therefore if the Low-E coating side is heated, the strength of the Low-E glass can be lowered.
2) Figure12 shows that by the data obtained from the fire test, relations with ΔT and the surface compression is led, the relation has a strong correlation by being classified in every emissivity value.
3) Figure15 shows that by consideration of glass surface heat balance, temperature reduction by Low-E coating is obtained, the relation of glass surface compression and temperature difference can be expressed in the same way as no coating glass.
4) Figure13 shows that radiant heat flux is lowered as the value of Emissivity of Low-E glass is Low, Low-E coating glass which has emissivity value 0.05±0.02 can reduce around 90% of radiant heat in comparison with no coating glass.
5) Figure24 shows that radiant heat flux from glass on fire can be explained by transmission of spectral characteristic of the radiant energy on fire and radiant heat flux from the unheated glass surface temperature. The radiant heat flux from a fire can penetrate no coating glass, that can’t do the Low-E coating glass with emissivity value 0.05±0.02. That is, if Low-E is coated on heating side, radiant heat flux depends only on the glass surface temperature.
In this study, the strength of glass was defined as glass surface compression. However not only the surface compression but also glass edge strength is very essential for glass breakage evaluation, so that needs further consideration.
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