Elucidating the effects of particle sizes on the fire extinguishing performance of core-shell dry water
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pISSN: 0256-1115 eISSN: 1975-7220
INVITED REVIEW PAPER
INVITED REVIEW PAPER
Elucidating the effects of particle sizes on the fire extinguishing performance of core-shell dry water Eungwoo Lee*,‡, Hyunwoo Son**,‡, and Youngbo Choi**,† *Korea Aerospace Research Institute, 169-84 Gwahangno, Yuseong-gu, Daejeon 34133, Korea **Department of Safety Engineering, Chungbuk National University, 1 Cungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Korea (Received 18 February 2020 • Revised 11 June 2020 • Accepted 11 July 2020) AbstractCore-shell dry water (DW) has attracted significant attention as a promising candidate for future fire extinguishing agents, owing to its high water content, powdery structure and ease of handling. However, the lack of detailed information regarding the characteristics of DW has considerably hindered efforts to improve its fire extinguishing performance. This study is the first attempt to elucidate the origin of the effects of particle size of DW on fire extinguishment. Pristine DW was fractionated into three different particle sizes via careful sieving. Through systematic analyses, it could be determined that smaller DW could be vaporized at lower temperatures, thereby facilitating good cooling and smoldering of flames. However, small DW cannot sufficiently penetrate flames, which makes it difficult to reach the burning surface. However, medium-sized DW exhibited a balance in its cooling, smoldering, and penetration effects. Thus, it achieved better performance in fire extinguishment when compared to small- and large-sized DWs. It was also demonstrated that the fire extinguishing capability of medium-sized DW can be significantly enhanced by adding NaHCO3 in the water core of the DW. Keywords: Hydrophobic Silica, Core-shell Dry Water, Fire Extinguishing Mechanism, Particle Size Effects, Chemical Additives
agent that has excellent fire extinguishing performance without detrimental side effects. Recently, there has been a growing interest in core-shell structured dry water (DW), which contains up to 98 wt% of water and exhibits characteristics similar to those of dry powders [9]. The core of DW is a significantly small water droplet with a porous shell of branched hydrophobic silica network that surrounds this water core [10]. It is considerably easy and convenient to handle and store DW because it maintains its powdery features even though it is mainly liquid water. The water core of DW can be released by evaporation or under mechanical stress [10]. Due to these characteristics, several studies have attempted to employ DW in various fields such as gas sensing [11], water pollution [12], storage and transportation [13,14], and fire extinguishing agents [15]. Dry core-shell DW has achieved excellent performance for extinguishing gasoline pool fires, and it is expected to possess sufficient scalability to enable its use in actual fire accidents [16]. Although previous studies have successfully demonstrated the potential of DW as a fire extinguishing agent, only a few studies have been able to un
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