• 설비공학논문집
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• 제10권4호
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• pp.475-482
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• 1998

In this paper, an experimental study was conducted to investigate the performance of the spherical ice particle production system which uses the technology of water spray in a vacuum chamber for increasing the heat transfer area. As a result, following conclusions were obtained. The diffusion-controlled evaporation model agreed relatively well with experiments. The spray flow rate influences the performance of the system rather than any other factors, for example, the spray nozzle position, the nozzle number. As the spray rate increases, the system efficiency increases. It is due to the entrainment of small droplets among the spray with the exhausted vapor. Thus the system should be designed and operated to prevent the entrainment. Assuming the compressor efficiency to be 70%, the COP of the system reaches highly up to 6 at a maximum spray rate. Under the conditions, however, the rigid ice layer is obtained because ice particles bond together with increase of the spray rate. Therefore, the spray rate should be controlled properly to make the spherical ice particles.

• 한국건축시공학회지
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• 제3권2호
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• pp.141-148
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• 2003

This study deals with the estimation of material properties according to the construction condition for water-soluble rubberized asphalt waterproofing material of spray type. In this study, the waterproofing material property by the spray construction method is suggested by means of estimation its tensile performance and temperature dependency according to mix proportion ratio(4:1, 8:1), referenced viscosity and solid content (A:360cps, 76%, B:580cps, 79%, C:490cps, 70%), spray angle($30^{\circ}$, $45^{\circ}$, $60^{\circ}$), and spray distance(30cm, 50cm, 70cm). The result of testing are as follows. (1) The mix proportion ratio of principal agent and hardener is 4:1. (2) The viscosity referenced and solid content are 490cps and 70%. (3) The spray angle referenced is $45.^{\circ}$ (4) The distance referenced from concrete surface to spray gun is 40~50cm.

• 한국분무공학회지
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• 제28권2호
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• pp.97-104
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• 2023

A sprinkler is a fire suppression system that extinguishes combustible materials in the early stages of a fire, creating a spray. However, spray formation method of the sprinkler can result in an uneven distribution of water spray on the surface of combustible materials. It is necessary to ensure a consistent water flux density regardless of the spray direction and angle. In this study, the water flux distribution was analyzed for the various types of sprinkler head: circular, flush, pendent, and upright types. All sprinkler heads have a K-factor of 80 LPM/(0.1MPa)^0.5. In this study, water collection cubes were used to examine the water flux distribution. The upright type sprinkler head showed a low standard deviation in total sprayed area, indicating a high level of uniformity. The upright type head showed the lowest standard deviation in the radial direction, and also showed the lowest standard deviation in the azimuthal direction. Upright sprinkler head has no obstructing structure along the path of droplets after they are generated. For this reason, upright sprinkler head showed the most uniform water flux distribution on the floor.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 춘계학술논문발표회 논문집
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• pp.218-221
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• 2008

The real scale fire suppression test inside a road tunnel were carried out for water spray systems. The dimension of the tunnel is 7.5m in height and 11.6m in width. 3 different water spray nozzle systems with low operating pressure less than 3.5 bar were used in the experiment. Two types of fires were tested. One is a $1.4m^2$ heptane pool fire and the other is a 2000CC passenger car fire. From the experiment, the spray densities of tested systems were about $6.0\;l/min/m^2$ which is currunt domestic guideline. Although all the systems cannot extinguish the tested fires, it was found that they can reduce the tunnel temperature and have a capability to control and suppress the tested fire.

• 한국분무공학회지
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• 제22권4호
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• pp.175-184
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• 2017

The numerical investigation on the effects of water-mist characteristics has been carried out for the fire suppression mechanism. The FDS are used to simulate the interaction of fire plume and water mists, and program describes the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The numerical model is consisted of a rectangular enclosure of $L{\times}W{\times}H=1.5{\times}1.5{\times}2.0m^3$ and a water mist nozzle that be installed 1.8 m from fire pool. In the present study, the parameters of nozzle for simulation are the droplet size and the spray velocity. The droplet size influences to fire flume on fire suppression more than the spray velocity because of the effect of the terminal velocity. The optimal condition for fire suppression is that the droplet size and the spray velocity are $100{\mu}m$ and 20 m/s respectively.

• 한국분무공학회지
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• 제13권3호
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• pp.143-148
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• 2008

In the present study, the correlation between the Nusselt number and Reynolds number was developed for forced convection and nucleate boiling region in spray cooling. Also the effect of droplet subcooling on spray cooling heat transfer was investigated. Full cone spray nozzles were employed for spray cooling experiment, and water and FC-77 were used for developing the correlation. From the experimental results, the correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for water and FC-77.

• Journal of Advanced Marine Engineering and Technology
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• 제24권5호
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• pp.25-32
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• 2000

In this paper, experiments investigating the high-temperature region heat transfer coefficients for the spray cooling of hot flat plates were performed by down spray water using flat spray nozzles. The heat transfer surface is made of copper and is 100mm in length and 40mm in width and 15mm in thickness. The experimental condition of spray are as follows: temperatures of the water droplets are T=20~$80^{\circ}C$ and droplets volume fluxes are D=0.001565~0.010438$m^3/m^2s$. Next, correlating equations for the heat transfer characteristics of spray cooling in the high temperature region are developed from the effects of droplets volume flux and the surface temperature of heat transfer plate.

• 한국분무공학회지
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• 제26권1호
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• pp.9-17
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• 2021

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.83-84
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• 2020

In present study, we have deposited the Zinc coating using arc thermal spray and plasma arc spray processes onto the steel substrate and durability of the deposited coating was evaluated. The bond adhesion result shows that plasma arc sprayed Zn coating exhibited higher in its value compared to arc thermal spray. SEM shows that Zn coating deposited by plasma arc process is more compact, less porous and adherent compare to arc spray process. The corrosion resistance properties are evaluated in artificial ocean water solution with exposure periods. EIS results show that total impedance at 0.01 Hz of plasma arc sprayed coating is higher than arc thermal spray owing to the compact and less porous morphology. It is concluded that plasma arc sprayed Zn coating is better than arc thermal spray process.

• 대한조선학회논문집
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• 제59권2호
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• pp.80-88
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• 2022

A systematic experimental study is carried out for the fire fighting monitor nozzle of 65A diameter to design and manufacture a new nozzle with better water spray performance than available domestic nozzles. The nozzle inlet pressure, flow rate and reach for the discharged water from the nozzle are measured by utilizing the experimental facility consisting of two pumps and piping system with a flow meter and pressure gauges. It was found that the baffle position and baffle head chamfering were the most sensitive design factors to be remarkably changed in the flow rate of the discharged water. Also, It was confirmed that the baffle position and the water exit area had the significant effect on the change in reach distance. The results obtained from this study are expected to be used effectively to design new nozzles with excellent spray performances and also to validate numerical analysis results for evaluating the water spray performance of fire fighting monitor nozzles.