Abstract
In this paper, the effect of initial water temperature on the cooling performance of a water mist fire suppression system has been investigated. A zero-dimensional analytical model was first developed to study the thermal and dynamic behavior of a single water droplet. The developed model was validated against available experimental data in the literature. The developed model was further extended to simulate the transient heating, evaporation, break-up, and liquid penetration length of a hollow-cone water spray. Results indicated that increasing the initial temperature of the water spray before injection resulted in a decrease in the initial size distribution of the spray droplets. It was further found that the evaporation time of the injected droplets decreased by about 11% and the cooling power of the pre-heated water mist system enhanced by 12% in exchange for increasing the initial temperature of the water spray by 10˚C. It was concluded that pre-heating the sprayed water droplets would likely improve the cooling efficiency of the water mist system. It could be also inferred that at equal cooling power, less water was consumed by the pre-heated spray compared to conventional water mist systems.
Highlights
Over the last decades, water spray systems have been utilized in a variety of applications within the areas of fire suppression, air conditioning, heat exchangers, and manufacturing processes [1,2,3,4,5]
The developed analytical model for a single water droplet was extended to a hollow-cone water spray by incorporating the Rosin-Rammler distribution function for calculating the droplet sizes at the nozzle exit
The primary purpose of the current study was to study the effect of the pre-heating of the sprayed water droplets on the water mist cooling efficiency
Summary
Water spray systems have been utilized in a variety of applications within the areas of fire suppression, air conditioning, heat exchangers, and manufacturing processes [1,2,3,4,5]. Water mist systems are one of the recent high-pressure water spray systems that are widely used in fire suppression applications. The water mist systems suppress the fire through three main factors: direct cooling of the fire, lessening the thermal radiation and oxygen displacement [6]. These factors are mainly prompted by the evaporation of the water droplets. Adiga et al [12] designed a numerically total flooding fire test for an ultra-fine water mist in a 28 m3 compartment Alongside these practical studies, some parametric investigations on fire suppression mechanisms have been done in small test scales [13,14]
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