Experimental studies on sprinkler and fire interaction

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Experimental studies on sprinkler and fire interaction


Author: Cheng, Sau-tong
Title: Experimental studies on sprinkler and fire interaction
Degree: M.Sc.
Year: 1997
Subject: Fire extinction
Fire sprinklers
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: x, 82, [138] leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1403335
URI: http://theses.lib.polyu.edu.hk/handle/200/4415
Abstract: Experimental studies on sprinkler and fire interaction under forced ventilated and nonventilated conditions were reported. A series of 23 burning tests with sprinklers were performed in the fire chamber of the Department of Building Services Engineering, The Hong Kong Polytechnic University. Three types of commercial sprinkler heads commonly used in Hong Kong including spray pendent, conventional and fast response were tested. Three different water pressure and flow settings in the sprinkler system, 1 bar at 4.2 m3hr-1, 0.7 bar at 3.42 m3hr-1 and 0.3 bar at 2.24 m3hr-1 were considered. The mass flux density, discharge distribution, droplet size distribution, response time of sprinkler, fire extinguishing time, air temperature variation in fire chamber and rate of fuel consumption were measured and analyzed. The effects of a sprinkler water spray on the stability of smoke layer and heat release rate of burning object were studied. Further, effects of venting on sprinkler performance were investigated. Experimental results indicate that the required design mass flux density of 5 mm min-1 was achieved when the water pressure and flow were set at 1 bar and 4.2 m3hr-1 respectively. At 0.7 bar and 3.42 m3hr-1, the required mass flux density is marginally within the range. All three types of sprinkler heads tested could reduce the heat within the range. All three types of sprinkler heads tested could reduce the heat generated by a fire source. However, the actuation time for the spray pendent and conventional types of sprinkler heads were much longer, meaning that it would take a long time to reach their nominal release values which were determined by immersing them in hot water bath heating at a rate of 0.5 C min-1. The traditional method in specifying the nominal release temperature of sprinkler head is not practical. A ratio of fire extinguishing time after sprinkler activated and the burning time of fuel without sprinkler installed was proposed to specify the performance of the sprinkler system. It was found that the higher the pressure and flow setting, the lower would be the ratio. The smoke layer interfacing height was found to be between 0.8 m to 1.0 m above floor level. The layer was disturbed by the operation of sprinkler spray and caused smoke logging. The results also show that the forced ventilation system studied in this project could increase the visibility in a fire environment, but would delay the operation of sprinkler.

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