Modelling Aspects of Sprinkler Spray Dynamics in Fires

doi:10.1205/095758204322972744

Process Safety and Environmental Protection

Volume 82, Issue 2, March 2004, Pages 97-104

https://doi.org/10.1205/095758204322972744 Get rights and content

Sprinklers are used extensively in a variety of fire protection applications. These systems are required to perform effectively over a wide range of extremely harsh and complex operating conditions. The sprinkler performance depends on the initiation, formation, dispersion and surface cooling characteristics of the sprays created by these devices. The behaviour of sprinkler sprays is strongly coupled with the fire dynamics in the surrounding environment, making characterization of these sprays and their corresponding performance quite challenging. The present paper provides a discussion of the important fundamental transport process for sprinkler sprays in fires. Mathematical models are provided for these processes in order to quantitatively characterize sprinkler spray performance. These mathematical models are well suited for incorporation into CFD codes or other fire modelling tools in order to analyze and predict fire suppression performance.

References (21)

T. Aihara et al.
Effect of droplets-size distribution and gasphase flow separation upon inertia collecting droplets by bluff-bodies in gas-liquid mist flow
Int J Heat Mass Transfer
(1986)
M. di Marzo et al.
Evaporative cooling due to a sparse spray
Fire Safety J
(1996)
M. di Marzo et al.
Evaporative cooling due to a gently deposited droplet
Int J Heat Mass Transfer
(1993)
N. Dombrowski et al.
The aerodynamic instability and disintegration of viscous liquid sheets
Chem Eng Sci
(1963)
G. Grant et al.
Fire suppression by water sprays
Prog Energy Combus Sci
(2000)
W.M. Grissom et al.
Liquid spray cooling of a heated surface
Int J Heat Mass Transfer
(1981)
V. Novozhilov
Computational fluid dynamics modeling of compartment fires
Prog Energy Combust Sci
(2001)
I.I. Paleev et al.
Phenomena of liquid transfer in two-phase dispersed annular flow
Int J Heat Mass Transfer
(1966)
M.R. Berry et al.
An integral analysis of condensing annular-mist flow
AIChE J
(1972)
C. Bonacina et al.
Dropwise evaporation, Trans ASME
J Heat Transfer
(1979)

There are more references available in the full text version of this article.

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The fire sprinkler head design was optimized using a micro-Genetic Algorithm to produce a uniform distribution of droplet size and water flux. The optimization process consisted of two steps. The first step optimized the injection pattern at a radial distance of 0.05 m from the center of the sprinkler head to produce a uniform water flux. In the second step, the sprinkler head design which produces the optimized injection pattern was derived. The optimized injection pattern was a sinusoid pattern with a large amplitude and wide width. Also, the water is targeted upward in the tine stream. The large amplitude of the injection pattern helped to achieve a uniform distribution of droplet sizes by delivering large droplets directly to the region near the sprinkler head at the floor level. Also, the water flux in the radial direction showed a more uniform distribution in the optimized design. The final optimized design shows that the section angle should be larger, the tines should be more protruding, and the slots should be more concave to improve the water flux distribution. Caution must be exercised in applying these results to conditions different from those used in this study.
Investigating the impact of oxygen concentration on fire dynamics using numerical simulation with FDS
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The world is experiencing an increase in demand for medical facilities due to the worsening of environmental and political conditions leading to emergencies that could suddenly increase the patients count in hospitals. The extensive use and storage of oxygen in hospitals and violation of the fire safety management practices lead to the occurrence and worsening of fire accidents. Though many researchers documented the influence of O₂ enrichment on fire dynamics, there are only limited studies present. This article attempts to investigate the effects of varying oxygen concentrations - 21% (v/v), 22% (v/v), and 23% (v/v) - on fire dynamics in a hospital environment using Fire Dynamic Simulator (FDS). The changes in Mass Loss Rate (MLR), Heat Release Rate (HRR), temperature profile, flash over occurrence and thermal intensity were reported and compared with varying oxygen concentration. The results show a significant increase in MLR and HRR with the increase in O₂ concentration, which directly contributed to the earlier occurrence of flashover. For oxygen concentrations of 21% (v/v), 22% (v/v), and 23% (v/v), the highest temperatures achieved were 1395 °C, 1421 °C, and 1494 °C and the thermal intensity values were found to be 966 kW.m^-2, 1027 kW.m^-2, and 1074 kW.m^-2, respectively. The variation in peak temperature and thermal intensity at 21% (v/v) and 23% (v/v) O₂ concentration, is found to be 7.1% and 11%, respectively. The findings provide a valuable insight that the oxygen concentration in a fire can impact the fire dynamics. This study can aid in the development of effective fire safety management systems for hospital environments. In addition, the process industries have a key role to play in supporting hospitals to adopt proper approaches, drawing on lessons learned from managing flammable and explosive atmospheres in chemical processes. These simulation results will give better understanding to adopt relevant safety codes for the hospitals.
Factors affecting water flux distribution of fire sprinklers and effect of water flux uniformity on fire suppression characteristics
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The water flux distribution of the sprinkler spray is not uniform due to the spray formation mechanism impinging on the deflector. In this study, the effect of factors such as installation height, flow rate, and deflector design on the uniformity of the water flux was investigated by experiment. Then, the water flux distribution has been reproduced with simulation and compared with measured data. When the installation height was increased, there was no significant change in the water flux pattern, only radial direction mixing. The water flux distribution predicted by changing the installation height through simulation showed excellent reproducibility with an R² value over 0.77. Increasing the flow rate maintained the water flux and its pattern near the sprinkler head, however increased the water flux away from the sprinkler head. The modified sprinkler deflector has a deep slot design that increases the water flux near the sprinkler head, which improves the water flux uniformity. Also, the large tines of the modified sprinkler deflector restored the flow after the frame arm, eliminating the effect of the frame arm.
Resolving the initial spray structure of fire sprinklers with a volume-of-fluid modeling
2022, Fire Safety Journal
Citation Excerpt :
Therefore, a large amplitude of waves was observed on the upper surface. The length measured diagonally from bottom to top of the surfaces was 955 μm, which is in a similar dimension of film thickness and corresponds to the droplet size(dv50) generally produced by sprinkler heads [38]. A strong vortex was formed before the ligament formation on the surface and it disappeared after disintegration.
The initial spray formation process of commercial fire sprinklers was investigated with a Large-eddy simulation and a Volume-of-Fluid model. The water-supply flow rate was set to 80 L/min corresponding to the minimum required flow rate in South Korea. From the study of grid dependency, a mesh size of 62.5 μm was adopted. Using this size of the mesh, unstable wave growth on the surface of the liquid sheet was captured, which corresponds to 1/16 the size of a sprinkler droplet that was derived in a previous study to be 1 mm. Sprinkler spray consisted of horizontal sheets generated by tines and vertical sheets generated by slots. Ligaments were produced by vortices on the air-water interface and droplets were generated by both longitudinal and lateral stretching. The flow rate of the tine section was larger than that of the slot section due to the large section angle. The water at the tine section was delivered to neighboring slot sections as flowing downstream. A formula for the sheet thickness was calibrated with measured mass outflow, which showed a more accurate value than the original formula driven by the mass conservation for the plate.
Effect of soot on thermal radiation shielding performance of water mist
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Citation Excerpt :
The shielding performance of water mists against intense radiation from fires has been extensively studied to devise water mist barriers that can effectively contain radiation [1–7]. Water spray can be distributed using various types of firefighting equipment, including sprinklers [8,9], portable blowers, blowing vehicles, self-defense sprays for firefighting vehicles, water screen hoses to prevent fire spread, drenchers for building facilities, and fire protection in coastal areas, such as on offshore installations or transport ships [10]. Soot is generated as a scattering medium in actual fires.
Water droplets and soot serve as important scattering media during fire suppression. From this standpoint, the present study sought to develop a method to determine the effect of soot smoke on the thermal radiation shielding performance of water mist. The radiative properties of single-diesel and propane soot particles and water droplets covered by soot were evaluated using the Mie scattering theory. The radiative transfer in the composite layer of mist and soot smoke was calculated. The analysis determined that the diameter of the primary or secondary soot particles affected the spectral reflectance of the water droplets, and the soot smoke layer and degree of soot dispersion affected the radiative transfer. The composite mist layer absorbed less thermal radiation than the uniformly dispersed mist and soot layer because smaller particles have a larger specific surface area, and can therefore adsorb more of the dispersed soot particles. Overall, the results could serve as a basis for the development of efficient mist barrier devices to prevent fire spread.
Protection from thermal radiation of hazardous fires: Optimizing microscale droplet size in mist barriers using radiative transfer analysis
2020, Process Safety and Environmental Protection
Citation Excerpt :
Water sprays have been widely used as an efficient shield against thermal radiation from fires. Water spray can be used within several firefighting equipments, including sprinklers (Marshall and di Marzo, 2004; Ruffino and diMarzo, 2004), pipes, portable blowers, blowing vehicles, self-defense sprays for firefighting vehicles, water screen hoses for preventing the spread of fire, drenchers for building facilities, and fire protection in coastal areas, on offshore installations or transported ships (Dombrovsky et al., 2020). Spray barriers are interposed between the source of radiation (fire) and burnable material to prevent fire spread.
The incidence of large-scale fires continues to rise, and the effects of radiation from these fires contributes to their continued spread. Water sprays have been widely used as an effective method to contain thermal radiation from fires. Results from previous studies on the sizes of water droplets in the spray barrier have limitations due to the significant computational time or complex analytical procedure involved. The aim of this study is to determine the optimal size of water droplets in the barrier mist using radiative transfer analysis for effective shielding of the radiation from the surroundings. The radiative properties of water droplets were analyzed using the Mie scattering theory and a radiative transfer analysis of the mist layer was performed. This demonstrated that the spectral reflectance of the mist layer can be controlled by the water droplet diameter. The effectiveness of optimizing the water droplet size in the mist layer to maximize protection from thermal radiation was also validated by experiments to evaluate the radiation shielding performance of the mist barrier.

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Review PaperModelling Aspects of Sprinkler Spray Dynamics in Fires

Int J Heat Mass Transfer

Fire Safety J

Int J Heat Mass Transfer

Chem Eng Sci

Prog Energy Combus Sci

Int J Heat Mass Transfer

Prog Energy Combust Sci

Int J Heat Mass Transfer

An integral analysis of condensing annular-mist flow

AIChE J

Dropwise evaporation, Trans ASME

J Heat Transfer

Review Paper
Modelling Aspects of Sprinkler Spray Dynamics in Fires