Experimental and numerical study of high-pressure water-mist nozzle sprays

Mahmud, H. M. Iqbal; Moinuddin, Khalid; Thorpe, Graham

doi:10.1016/j.firesaf.2016.01.015

Cited by 27 publications

(10 citation statements)

References 7 publications

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“…The water droplets may become unstable under the action of aerodynamic forces induced by their motion in the continuous phase. According to Hsiang and Faeth model [31], breakup takes place if We = > 12 (20) and, the droplet diameter changes due to secondary breakup can be calculated from [31]:…”

Section: The Secondary Breakup Of Dropletsmentioning

confidence: 99%

“…Researches have shown that the efficiency of the water mist systems can be considerably influenced by the injection conditions at the nozzle exit [15]. Using additives and chemicals [16,17], changing the characteristics of nozzle [18,19] and increasing the backpressure of the nozzle [20] are among the most important ways proposed to reduce the droplet mean diameter and change the initial size distribution at the nozzle exit. In addition to the above-mentioned factors, the initial droplet size distribution is largely dependent on the thermophysical properties of the water.…”

Section: Introductionmentioning

confidence: 99%

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A Simulated Study on the Effect of Water Temperature on Cooling Efficiency of Water Mist Fire Extinguishers

Omidvar

Mahdavi

Mehryar

2020

Journal of Thermal Engineering

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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 preheated 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.

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Section: The Secondary Breakup Of Dropletsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Simulated Study on the Effect of Water Temperature on Cooling Efficiency of Water Mist Fire Extinguishers

Omidvar

Mahdavi

Mehryar

2020

Journal of Thermal Engineering

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“…The water-mist spray comprises fine mists with a higher surface area/volume ratio, resulting in rapid evaporation [2]. However, the efficacy of water-mist sprays in suppressing fires is strongly influenced by the characteristics of the sprays [3,4]. These characteristics are ultimately governed by the initial spray parameters [5].…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, computational fluid dynamics (CFD) models have been increasingly used to investigate the growth and suppression of fires, including the dynamics of sprays [3]. There can be an alternative way to use a CFD-based model to determine the spray parameters of a water mist nozzle.…”

Section: Introductionmentioning

confidence: 99%

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An Approach to Determine the Median Diameter of Droplets in a Water-Mist Spray

2022

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The physical characteristics of water sprays profoundly influence the efficacy with which fires are extinguished. One of the most important physical characteristics of water sprays is the median diameter of the water droplets. However, this parameter is difficult to measure without resorting to the use of specialised equipment. Furthermore, the distribution of the size of water droplets and their initial velocity are profoundly sensitive to the pressure at the nozzle head. This paper presents a simple technique to determine the median droplet size of a water spray produced by a nozzle. The method required only two experiments to determine the mass flux distribution generated by a nozzle operating at two known pressures. A computational fluid dynamics (CFD) program was then used to estimate the median diameter of the water spray under these conditions. The median droplets generated when the nozzle was operating under a different pressure can be calculated using an established empirical relationship. The approach advocated in this paper is supported by invoking Whewell’s principle of consilience of inductions. This was achieved by observing that the CFD software accurately predicts the mass flux distribution when the new pressure and estimated median diameter of the droplets were used as inputs. This provides independent evidence that the proposed approach has some merit. The findings of this research may contribute to establish a technique in calculating the median diameter of droplets when direct measurement of droplet diameter is not available.

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