Analysis on Practical Thermal Responsiveness of the Glass Bulb Sprinklers

In Taiwan, qualified glass bulb sprinklers must be validated by the Approval Criteria for Close Sprinkler Head. However, the actuation temperature marked on the sprinkler head is the temperature as tested in water, not the ordinary air temperature In the actual scene of the fire. The difference in the thermal conductivity between water and air is 23 times. This study uses heat transfer principles for derivation and FDS software for a thermal responsiveness analysis of glass bulb sprinklers. Fire loads of 0.5, 1.5 and 2.5 MW are simulated with both ultra-fast and slow burning rates; the cracking temperature of the glass bulb and the hot air velocity are recorded. The results show that there are significant differences in actuation and detecting environment when the sprinklers head contact the hot air at the fire scene. The marked detection result can only serve as a qualification because of the differences in fluid properties. In addition, the actuation time of the sprinkler head is closely related to the burning rate.