• Journal of the Korea Safety Management & Science
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• v.26 no.1
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• pp.31-38
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• 2024

In this paper, as there are many cases of fires occurring due to the failure or inoperability of the thermostat of electronic products, the purpose is to test and analyze the risks and probabilities through fire cases and reproduction experiments, and suggest countermeasures. Among electronic products, water purifiers are composed of a refrigerant system with a compressor to make cold water, a heating device to make hot water, and an electric device used as an energy source. Due to the nature of the water purifier manufacturing, these devices are subject to a lot of moisture and dust. etc. exist in large quantities and use electrical energy, so there is a possibility of fire due to short circuit in the wire, electrical abnormal overheating (tracking phenomenon) in the thermostat, electronic board, starting relay, etc., and overheating of the heating device (Band Heater). there is. Therefore, in order to prevent fires from these devices, a system to remove foreign substances inside the water purifier is necessary, the use of heat-resistant (fire-resistant) wires for electrical devices is essential, and the use of non-combustible materials (semi-combustible materials) for each part is necessary to prevent fire. The risk must be eliminated through prevention and combustion expansion prevention devices.

• Current Optics and Photonics
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• v.8 no.2
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• pp.138-150
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• 2024

This study is essential for advancing our knowledge about the interaction between long-range high-power lasers and energetic materials, with a particular emphasis on understanding the response of a 155-mm shell under various surface irradiations, taking into account external factors such as atmospheric disturbances. The analysis addresses known limitations in understanding the use of non-realistic targets and the negligence of ambient conditions. The model employs the three-dimensional level-set method, computer-aided design (CAD)-based target design, and a message-passing interface (MPI) parallelization scheme that enables rapid calculations of the complex chemical reactions of the irradiated high explosives. Important outcomes from interaction modeling include the accurate prediction of the initiation time of ignition, transient pressure, and temperature responses with the location of the initial hot spot within the shell, and the relative magnitude of noise with and without the presence of physical ambient disturbances. The initiation time of combustion was increased by approximately a factor of two with atmospheric disturbance considered, while slower heating of the target resulted in an average temperature rise of approximately 650 K and average pressure increase of approximately 1 GPa compared to the no ambient disturbance condition. The results provide an understanding of the interaction between the high-power laser and energetic target at a long distance in an atmospheric condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.740-746
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• 2017

Infrared signatures emitted from hot exhaust gases generated by the internal combustion engine and generator of naval ships and from the metal surfaces of the funnel have become the targets of infrared homing missiles, which is the main cause of a reduced survivability of naval ships. The infrared signatures from the exhaust gas and the metal surface of a funnel can be reduced by installing an infrared signature suppression (IRSS) system on a ship. The IRSS system consists of three parts: an eductor that generates turbulent flow of the exhaust gas, a mixing tube that mixes the exhaust gas with ambient air, and a diffuser that forms an air film using the pressure difference between the inside and outside air. As a basic study to develop an IRSS system using domestic technology, this study analyzed the model test conditions of an IRSS system developed by an overseas engineering company and installed on a domestic naval ship, and a numerical heat-flow analysis was conducted based on the results of the aforementioned analysis. Numerical heat-flow analysis was performed using a commercial numerical-analysis application, and various turbulence models were considered. As a result, the temperature and velocity of the exhaust gas at the educator inlet and diffuser outlet and that of the metal surface of the diffuser were measured, and found to agree well with the measurement results of the model test.

• Fire Science and Engineering
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• v.18 no.3
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• pp.30-38
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• 2004

An important characteristics during fire growth is the phenomena of flashover, which is the transition from the local combustion to the full-room fire. The aim of this study is to predict the flashover times, the ignition times and HRR(heat release rate) of flashover for building interior materials. By using the literature data and RSM(response surface methodology), the new equations for predicting the flashover time, the ignition time and the HRR of building interior materials are proposed. The A.A.P.E.(average absolute percent error) and the A.A.D.(average absolute deviation) of the reported and the calculated flashover times were 38.74sec and 51.24sec respectively, and the correlation coefficient was 0.975. The A.A.P.E and the A.A.D of the reported and the calculated ignition times were 10.96sec and 1.97sec, and the correlation coefficient was 0.962. Also the A.A.P.E and the A.A.D. of the reported and the calculated the HRR of flashover by means of times were 29.92 and 514, and the correlation coefficient was 0.830. The values calculated by the proposed equations were in good agreement with the literature data. Therefore, it is expected that this proposed equations will support the use of the research for other building interior materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.563-569
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• 2012

The superheater and reheater tubes of a heavy-load fossil power plant boiler can be damaged by overheating, and therefore, the degree of overheating is assessed by measuring the oxide scale thickness inside the tube during outages. The tube temperature prediction from the oxide scale thickness measurement is necessarily accompanied by destructive tube sampling, and the result of tube temperature prediction cannot be expected to be accurate unless the selection of the overheated point is precise and the initial-operation tube temperature has been obtained. In contrast, if the tube temperature is to be predicted analytically, considerable effort (to carry out the analysis of combustion, radiation, convection heat transfer, and turbulence fluid dynamics of the gas outside the tube) is required. In addition, in the case of analytical tube temperature prediction, load changes, variations in the fuel composition, and operation mode changes are hardly considered, thus impeding the continuous monitoring of the tube temperature. This paper proposes a method for the short-term prediction of tube temperature; the method involves the use of boiler operation information and flow-network-analysis-based tube heat flux. This method can help in high-temperaturedamage monitoring when it is integrated with a practical tube-damage-assessment method such as the Larson-Miller Parameter.

• Plant Journal
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• v.13 no.2
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• pp.46-51
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• 2017

In this study, the boiler efficiency and the change of boiler combustion state with the burner operation of the uppermost layer of 870MW opposite fired coal boiler were measured. Test results showed that the boiler efficiency was high in the order of the uppermost layer simultaneous operation of the front and rear burners, the front burner, and the rear burner operation. When the front and rear burners were operated simultaneously, the heat absorption rate of water walls in the boiler furnace was uniform at four side, and the temperature deviation of the left and right steam on the convection front surface decreased. As the heat absorption rate of the boiler improved, the loss of boiler exhaust gas decreased and the coal supply amount decreased by 8 tons/hour compared to the operation of the rear burner. This will contribute not only to the reduction of fuel cost but also to the reduction of greenhouse gas emissions.

• Fire Science and Engineering
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• v.33 no.1
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• pp.69-75
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• 2019

In this study, the combustibility of five types of plastic plates, fiber reinforced plastic (FRP), polystyrene (PS), polycarbonate (PC), polypropylene (PP), and polyvinyl chloride (PVC), were tested using a cone calorimeter (ISO 5660). The PVC plate showed a $44.65kW/m^2$ lower peak heat release rate (HRR) and a $30.97kW/m^2$ lower maximum average rate of heat emission than the other four types of plastics, whereas the PS plate showed a $773.44kW/m^2$ higher peak HRR and $399.14kW/m^2$ higher maximum average rate of heat emission. The PC plate and PS plate showed the highest HRR by a maximum of 3.88 times in $CO_{mean}$ yields, while the PS pate and PP plate showed the highest HRR by a maximum 4.88 times in $CO_{2mean}$ yields. In addition, the smoke performance index (SPI) of the PS plate decreased by 74.81%~95.99%; the smoke growth index (SGI) increased to 76%~300%; the smoke intensity (SI) also increased to 917.73% ~ 9607.57%, and the danger of smoke increased. The PS plate was found to have the highest risk of life damage due to smoke on the thermal and smoke sides.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.639-647
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• 2022

The use of flames is essential in cutting, bending, and welding steel during a ship's construction process. While acetylene fuel is commonly used in steel cutting and the manufacturing process in shipyards, the use of propane as an alternative fuel has recently been increasing, due to the lower risk of explosion and propane's relatively low calorific value. However, propane fuel has a relatively slow processing speed and high slag generation frequency, thereby resulting in poor quality. Propylene is another alternative fuel, which has an excellent calorific value. It is expected to gain wider use because of its potential to improve the quality, productivity, and efficiency of steel processing. In this study, the combustion characteristics of propane and propylene fuel during steel plate processing were analyzed and compared. The reduction of greenhouse gases and other harmful gases when using propylene flame was experimentally verified by analyzing the gases emitted during the process. Heat distribution and tensile tests were also performed to investigate the effects of heat input, according to processing fuel used, on the mechanical strength of the marine steel. The results showed that when propylene was used, the temperature was more evenly distributed than when propane fuel was used. Moreover, the mechanical tests showed that when using propylene, there was no decrease in tensile strength, but the strain showed a tendency to decrease. Based on the study results, it is recommended that propylene be used in steel processing and the cutting process in actual shipyards in the future. Additionally, more analysis and supplementary research should be conducted on problems that may occur.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.73-84
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• 2018

Recently, the importance of flame retardation treatment technology has been emphasized due to the increase in urban fire accidents and fire damage incidents caused by building exterior materials. Particularly, in the utilization of wood-based building materials, the flame retarding treatment technology is more importantly evaluated. An Intumescent system is one of the non-halogen flame retardant treatment technologies and is a system that realizes flame retardancy through foaming and carbonization layer formation. To apply the Intumescent system, composite material was prepared by using Ethylene vinyl acetate (EVA) as a matrix. To enhance the flame retardant properties of the Intumescent system, a nano-clay was applied together. Composite materials with Intumescent system and nano - clay technology were processed into sheet - like test specimens, and then a new structure of cross laminated timber with improved flame retardant properties was fabricated. In the evaluation of combustion characteristics of composite materials using Intumescent system, it was confirmed that the maximum heat emission was reduced efficiently. Depending on the structure attached to the surface, the CLT had two stages of combustion. Also, it was confirmed that the maximum calorific value decreased significantly during the deep burning process. These characteristics are expected to have a delayed combustion diffusion effect in the combustion process of CLT. In order to improve the performance, the flame retardation treatment technique for the surface veneer and the optimization technique of the application of the composite material are required. It is expected that it will be possible to develop a CLT structure with improved fire characteristics.

• Clean Technology
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• v.25 no.3
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• pp.245-255
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• 2019

Pressurized oxy-fuel combustion is a promising technology for $CO_2$ capture with a benefit of improving power plant efficiency compared with atmospheric oxy-fuel combustion. Prior to $CO_2$ compression in this process, a flue gas condenser (FGC) is used to remove $H_2O$ while recovering the latent heat. At the same time, the FGC has a potential for high-efficiency removal of $SO_x$ and $NO_x$ by exploiting their good solubility in water. In this study, experiments were carried out in a lab-scale, direct contact FGC under different pressures varying between 1 and 20 bar to evaluate the removal efficiency of $SO_2$ and $NO_x$ for individual gases and their mixture. In the tests for individual gases, 20% and 76% of $NO_x$ was removed at 1 bar and 10 bar, respectively. Even higher removal efficiencies were achieved for $SO_2$, and also these were maintained for longer as the pressure increased. In the tests for $SO_2$ and $NO_x$ mixture, the removal efficiency of $NO_x$ increased from 13% at 1 bar to 56% at 20 bar because of higher solubility at elevated pressures. $SO_2$ in the mixture was initially dissolved almost completely and then increased by 1,219 ppm at 1 bar and by 165 ppm at 20 bar. Overall, the removal efficiency of $SO_2$ and $NO_x$ was increased at elevated pressures, but it was lower in the mixture compared with individual gases at identical conditions because of a lower pH and associated chemical reactions in water.