Assessment of fire protection performance of water mist applied in exhaust ducts for semiconductor fabrication process

Shu, Yi Liang; Jeng, Wei Jin; Chiu, Chen Wei; Chen, Chiun-Hsun

doi:10.1002/fam.890

Cited by 4 publications

(3 citation statements)

References 5 publications

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“…Water-mist droplets can cool the surrounding air and attenuate thermal radiation, and the water vapour produced by evaporation reduces the fuel vapour/air ratio by displacing oxygen [22][23][24][25][26][27]. Evidence supports the idea that water-mist spray can remove 100% of the heat produced by a fire either by extinguishing it or allowing enough evaporation to keep the compartment's temperature at or below the boiling point of water [21,28].…”

Section: Introductionmentioning

confidence: 99%

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

Mahmud

Thorpe

Moinuddin

2022

Fire

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This paper presents work on investigating the effect of the initial size of water mist droplets on the evaporation and removal of heat from the fire-induced hot gas layer while travelling through the air in a compartment. The histories of the temperature, diameter and position of droplets with different initial diameters (varied from 100 µm to 1000 µm) are determined considering surrounding air temperatures of 75 °C and 150 °C and a room height of 3.0 m. A water droplet evaporation model (WDEM) developed in a previous study (Fire and Materials 2016; 40:190–205) is employed to navigate this work. The study reveals that tiny droplets (for example, 100 µm) have disappeared within a very short time due to evaporation and travelled a very small distance from the spray nozzle because of their tiny size. In contrast, droplets with a larger diameter (for example, 1000 µm) reached the floor with much less evaporation. In the case of this study, the relative tiny droplets (≤200 µm) have absorbed the highest amount of energy from their surroundings due to their complete evaporation, whereas the larger droplets have extracted less energy due to their smaller area/volume ratios, and their traverse times are shorter. One of the key findings of this study is that the smaller droplets of spray effectively cool the environment due to their rapid evaporation and extraction of heat from the surroundings, and the larger droplets are effective in traversing the hot air or smoke layer and reaching the floor of the compartment in a fire environment. The findings of this study might help in understanding the behaviour of water-mist droplets with different initial diameters in designing a water-mist nozzle.

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Section: Introductionmentioning

confidence: 99%

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

Mahmud

Thorpe

Moinuddin

2022

Fire

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“…Due to its advantages of cleanness and good fire suppression effectiveness, water mist fire suppression technology has been a subject of many investigations over the last decade 18‐24 . Many achievements have been made in the methods of generating water mist, the measurement of spray characteristics, the fire suppression mechanisms and effectiveness, the influence factors, etc 17,25‐34 . However, the low pressure water mist systems with higher water flow rates, larger droplet sizes, high cost pipe network and nozzle and high requirements for water quality, are barely used in industrial and building fire, hence the applicability of water mist under low pressures has not been given enough research attention.…”

Section: Introductionmentioning

confidence: 99%

Pool fire suppression performance by twin‐fluid water mist under low pressures in an altitude chamber

Wan

Shao

et al. 2020

Process Safety Progress

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Fire suppression tests using low pressure twin‐fluid water mist under low pressure environments were carried out to exam the performance of water mist systems at low pressure environments. The experiment results show that the suppression time gets shorter for lower chamber pressure, and relevant total weight of water and nitrogen used decreases as the chamber pressure gets lower. For the case of 30‐cm diameter pool fire, the suppression times are 20.19, 7.5, and 2.24 under the chamber pressure of 60, 38, and 24 kPa, respectively. In case of a cargo compartments fire, it is suggested to open the ventilation valve of the cargo compartment at a high cruising altitude to relieve pressure, so as to achieve rapid fire suppression. When a fire happens at the position off the center below the water mist nozzle, the water mist suppression effects will be weakened. The fire size has little effects on the fire extinguishing process under pressure of 24 kPa. Under the critical atomization condition with the pressure differential between the inlet and outlet of the nozzle for water as 0.05 MPa (5.04 L/min), and the pressure differential for nitrogen as 0.10 MPa (10.97 L/min), the suppression time is the shortest as 18.66 seconds.

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“…The performance of WMFSS depends on many interacting factors, such as the mass flow rate of water, and the diameters, velocities and spatial distributions of the droplets. The droplets have the potential to cool the surrounding air, attenuate thermal radiation and the water vapour produced by evaporation reduce the fuel vapour/air ratio by displacing oxygen [1][2][3][4][5][6][7][8]. Not all droplets evaporate before striking burning surfaces, and this provides a direct method of suppressing fires [2,3,6,7,9,10].…”

Section: Introductionmentioning

confidence: 99%

Study of water‐mist behaviour in hot air induced by a room fire: Model development, validation and verification

2014

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Summary Water‐mists are emerging as an effective agent for the suppression of fires. However, the mechanisms of suppression are complex and the behaviour of individual water droplets in a smoke layer generated by fires must be quantified. This study investigates the behaviour of individual droplets injected from a nozzle into a hot air environment induced by a room fire. A semi‐empirical model has been developed based on the conservation of mass, momentum and energy to evaluate the heat and mass transfer phenomena in an air‐water droplet system. The model has considered the effect of change of momentum of an evaporating droplet. A forward finite difference approach is applied to solve the governing time dependent ordinary differential equations. The droplets are considered to be ‘lumped mass’ and variable thermo‐physical properties of water and air and the change of Reynolds number of the droplets, due to the change of their diameter and velocity are considered. The effect of high evaporation rate on the mass and heat transfer coefficient and the contribution of radiation emanating by a flame and the surrounding boundary walls are also considered in the model which were not taken into account in the previous studies. Experimental data on terminal velocity and adiabatic saturation temperature are used to validate and verify the model. The validation and verification indicate that the proposed model predicted the terminal velocity within 4% of the experimental data and predicted the saturation temperature within 5% of the adiabatic saturation temperature. This semi‐empirical model is also used as a tool to validate a more comprehensive computational fluid dynamics (CFD) based tool, Fire Dynamics Simulator (FDS). It is found that FDS results agree well with the results of the proposed model. Furthermore, the proposed model can be used to evaluate the temperature, velocity, diameter and other physical properties of a droplet travelling through a layer of hot air. Copyright © 2014 John Wiley & Sons, Ltd.

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Assessment of fire protection performance of water mist applied in exhaust ducts for semiconductor fabrication process

Cited by 4 publications

References 5 publications

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

Pool fire suppression performance by twin‐fluid water mist under low pressures in an altitude chamber

Study of water‐mist behaviour in hot air induced by a room fire: Model development, validation and verification

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