• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.2
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• pp.244-249
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• 2000

Thermal gradient chemical vapor infiltration (TG-CVI) process, which is one of the CVI techniques to densify a porous fiber preform, requires for a heater to have uniform surface temperature distribution. Thus, it is essential to design the shape of the heater and to predict the temperature distribution when the heater has a profile which is not a simple cylinder. In this study, an analytical method has been used to design the inner profile of a conical heater showing uniform temperature distribution, if its outer shape is specified. Temperature distribution on the heater surface has been calculated with the finite difference method and compared with the experimental results. When a heater had a combined profile with a large cone and a small cylinder, temperature was higher in the cylindrical part. To reduce the temperature difference between these areas, a hole-machining method has been proposed including other possible ones. A shape design and optimization program has been made to improve the temperature uniformity of the TG-CVI heater better than that designed with the analytical method.

• Journal of the Korean Society of Safety
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• v.22 no.6
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• pp.46-54
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• 2007

The purpose of this study was to examines the burning rate of fire retardant treated wood in the cone heater with a one-dimensional integral model. The wood samples used in this study were four species. The species of woods are Redwood, White oak, Douglas fir and Maple. Each sample was nominally 50mm thick and 100mm square. Samples were exposed to a range of incident heat fluxes 10 to $35kW/m^2$ using the cone heater. A one-dimension integral model has been used to predict burning rate, heat of gasification, flame heat fluxes, charring rate and char depth of samples. As a result measurement of mass loss rate, softwoods(Redwood and Douglas fir) has relatively low value than those for hardwoods(White oak and Maple). Average charring rate of woods in case of fire retardant treatment showed reduction effect of 41.29%, 50.00%, 48.18% and 60.82% for Redwood, Douglas fir, White fir and Maple, respectively. Almost all the predictions from integral model showed faster charring than those measured. Average difference between predictions and experimental data was 16%, 9.5% and 11.8% for N, F1 and F2 respectively. Water-soluble fire retardant used in this study find out more effect in hardwood than softwood from the result of measurement of mass loss rate and average charring rate.

• Fire Science and Engineering
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• v.18 no.4
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• pp.86-92
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• 2004

We tested five specimens of each species at each of five constant external heat flux levels (10, 15, 20, 25. and 35㎾/㎡). An Cone heater was used to expose the wood specimens to the heat flux. The 100-by 100-by 50-㎜ specimens were of four species: Redwood, White oak, Douglas fir, Maple. In result of test, charring of wood exposed to a constant external heat flux can be considered a linear with function of time. As compared with the charring rates Redwood is most rapidly, but on the other hand Douglas fir is most slowly. When the external heat flux is 35㎾/㎡, the charring rate is rapidly about twice then 10㎾/㎡. Using the Equation (2), the estimates for u were 1.02, 1.16, 1.23, 1.32, and 1.44 for the 10, 15, 20, 25, and 35 kw/m2 constant external exposure levels, respectively.

• Fire Science and Engineering
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• v.24 no.3
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• pp.39-44
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• 2010

The cone calorimeter method which is currently used to measure the heat release rate has a fixed rate of radiation. However, in the real fire, when flame combustible material burns, it releases the identical heat flux. We measured the changes of temperature of a fire using FDS in order to analyze flexible heat flux of combustion characteristics. In this study, the rate of radiation of cone calorimeter was adopted by using FDS. Follow those results, it produce between the rate of radiation in the growth period and decline period have a significant impact on heat release rate of PMMA.

• Fire Science and Engineering
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• v.24 no.3
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• pp.52-57
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• 2010

Fire protection countermeasure were considered on the straw thatched roof and wooden structure. For the fire resistant treatment, rice straw was soaked in the fire resistant liquid with different soaking time. After treatment, some rice straw sample was washed with water then the rice straws were tested to check the fire resistance performance. And the wood was soaked in the fire resistant liquid at an atmospheric pressure, vacuum-pressure condition and painted with brush on the surface. To analyse the fire resistant performance of rice straw, ignition delay time was measured under the radiant heat flux of cone heater. And the fire resistant performance of wood samples were tested with 45 degree fire resistant test apparatus and cone heater. Based on the cone heater test, the rice straw which most easily ignitable material shows the longer ignition delay time than not treated ones and even in the water washed straw show a longer ignition delay time than not treated ones. And fire resistant treated woods of vacuum-pressure treated sample showed the most excellent performance on fire resistance. And the fire resistant treated by brush and soaking showed a longer ignition delay time than not treated ones. From this experiment, it was found that a fire resistant treatment of rice straw and wood of the house can be protected from the fire spread.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.179-184
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• 2007

The boiling heat transfer was experimentally investigated for the FC-77 sprays impacting a square heated test surface in a downward direction. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made under the test conditions of $Q=3.32{\times}10^{-6}{\sim}2.30{\times}10^{-5}\;m^3/s$, ${\Delta}T_{sub}=20{\sim}70^{\circ}C$. Also, heat transfer measurements were made using the copper block of $10{\times}10\;mm^2$ test area heated by nine cartridge heater. From the experimental results, 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 FC-77.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.938-944
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• 2008

The boiling heat transfer was experimentally investigated for the PF-5052 sprays impacting a square heated test surface in a downward direction. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made under the test conditions of Q=$3.32{\time}10^{-6}{\sim}\;12.98{\time}10^{-6}m^3/s$, ${\Delta}T_{sub}=5{\sim}25^{\circ}C$. Also, heat transfer measurements were made using the copper block of $10{\time}10mm^2$ test area heated by nine cartridge heater. From the experimental results, 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 PF-5052.

• Journal of the Korean GEO-environmental Society
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• v.13 no.10
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• pp.43-53
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• 2012

This study deals with the conventional consolidation methods like preloading and vertical drains. For it, Two different mechanism, i.e., increasing of permeability and evaporating of pore water were studied. The marine clays excavated in Incheon were heated at low temperature($90^{\circ}C$) to increase the permeability. Also, Microwave oven and high-temperature electric heater were used for pore water evaporation. Several points raised from the experiments. To fix them, the electric heating system was revised to upgrade the field application and drain efficiency of pore water, and the marine clays were heated by revised electric heater at high temperature($250^{\circ}C$). From Experimental result showed that results, high-temperature heater induced the pore water evaporation and displayed the excellent consolidation behavior. In addition, the cone index of heated clays were increased about 19 times, which suggested that electric heating system could be applied for ensuring the trafficability of heavy equipments.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.98-104
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• 2005

This study experimentally and theoretically examines the fire characteristics of 100- by 100- by 50-mm samples of flame retardant treated Douglas fir. Samples were exposed to a range of incident heat fluxes 10 to $50kW/m^2$. The time to ignition measurements obtained from the cone heater were used to derive characteristic properties of the materials. A one-dimensional integral model has been used to predict the, time to ignition, critical heat flux and ignition temperature of samples. Ignition data and best-fit curves confirm ${{\dot{q}}_i}^{'}{\rightarrow}{{\dot{q}}_{cr}^{'}\;then\;t_{ig}{\rightarrow}{\infty}$ and when ${{\dot{q}}_i}^'{\gg}{{\dot{q}}_{cr}^'\;then\;t_{ig}{\rightarrow}0$. And Ignition of flame retardant treated samples occurred not at incident heat flux of bellow $10kW/m^2.$. By a one-dimensional integral model, the critical heat flux of each samples was predicted $10.21kW/m^2,\;11.82kW/m^2,\;and\;14.16kW/m^2$ for the D-N, D-F2, and D-F4, respectively. In ignition temperature of each samples, flame retardant treated samples were measured high about $50^{\circ}C$ than non-treated samples. Water-soluble flame retardant used in this study finds out more effect in delay of time to ignition when incident heat flux is low than high.

• Fire Science and Engineering
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• v.27 no.6
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• pp.15-20
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• 2013

The convective heat transfer coefficient, emissivity, and flame heat flux on the surface of Duglas fir are estimated by using repulsive particle swarm optimization. The surface temperature, mass loss rate, and ignition time are measured for various incident heat fluxes from a cone heater of the cone calorimeter. The calculated surface temperatures obtained by using the optimized convective heat transfer coefficient, emissivity and flame heat flux on the surface in this study match well with those obtained from the test. The maximum error between the predicted and measured surface temperatures for the three different external heat fluxes is within 2% showing reasonable agreements. The methodology proposed in this study can be used to obtain various values related to heat transfer on a flaming surface that are difficult to measure in experiments.