• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.8
• /
• pp.99-109
• /
• 2022

In this study, an electric resistance-heated surface friction spot-welding process was proposed and tested for the spot-welding ability of copper and aluminum dissimilar metal sheets using electric resistance heating and surface friction heating. This process has welding variables, such as the current value, energizing cycles, rotational speed, and friction time. The current value and energizing cycle can affect the resistance heat, and the rotational speed of the rotating pin and friction time influence frictional heat generation. Resistance heating before friction heating has a preheating effect on the Cu-Al contact interface and a positive effect on preventing friction heat loss during the friction stage. However, because resistance preheating can soften the copper sheet and affect the contact stress and friction coefficient, it has difficulties that may adversely affect frictional heat generation. Therefore, the optimal combination of welding variables should be determined through simulations and experiments of the spot-welding process to determine the effects of electric resistance preheating on the suggested process. Through this procedure, it is known that the proposed spot-welding process can improve the welding quality during the spot welding of Cu-Al sheets.

• Journal of the Korean Society of Safety
• /
• v.33 no.3
• /
• pp.15-20
• /
• 2018

There have been a number of major fatal fire accidents in Korea recently. The number of fires in 2017 were 44,178, which is not only increasing number of fires but also increasing in casualties. Particularly, the fire at Jecheon Sports Center, which suffered many casualties, is expected to have a huge impact. The cause of the fire has not been determined yet, but heat waves on the ceiling have also been pointed out. As such, the copper heating waves, which are used as a preventive measure against damage of pipes due to freezing of pipes, etc., always have a fire hazard. To determine the possibility of a flame-resistant heated fire, a positive electric cable product was used to artificially ignite and analyze the results. In case of a short circuit, the external covering of the positive electric cable is damaged, but not short circuit unless the heating material surrounding the wire is damaged. Due to the characteristics of heating cable for preventing copper waves, the chances of insulation becoming more severe due to moisture and temperature changes are higher than normal wires. If the internal heating system is carbonized by insulating deterioration without damage to the outer coating, it is likely to cause trekking, to form a winding loop in the heating materials, and to cause short circuit in the heated materials. For the positive temperature line, if the middle is shorted, the current continues to flow to the short circuit unless the breaker disconnects. Consequently, a heated fire that does not cut off the power immediately may leave multiple marks or cuts.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.9
• /
• pp.4197-4203
• /
• 2013

In order to investigate the heating performance of multi-heat pump applying an inverter compressor, the experiment on heat pump with 3 indoor units was performed under the heating standard and heating low-temperature conditions. The performance data of heat pump with 3 indoor units were measured by the multi-psychrometric calorimeter. The operation characteristics and the behavior of the refrigerant cycle of the heat pump with 3 indoor units were understood from the heating capacity, heating COP, and P-h diagram by indoor-unit combination. The present experimental results show that the operating load and performance of the multi-heat pump depends on the indoor-unit combination. The heating capacity and heating COP of the low temperature condition were smaller than those of the standard one. Also the refrigerant cycles on indoor-unit combination were analyzed by using P-h diagram.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.20 no.1
• /
• pp.77-84
• /
• 2006

For a fire cause judgement this paper describes the heating characteristics of electric bare wire melted by AC current. The cower wires prepared for the experiment were 1.2[mm], 1.6[mm], and 2.0[mm] in diameter. Through the cross section analysis(CSA), it was confirmed that the dendrite structure grew at the angle of about 40[$^{\circ}$] or 60[$^{\circ}$] when the fusing current was applied to the wires. The larger the fusing current is, the more decreased the growth angle of the dendrite structure is. It was confirmed that the dendrite structure was arranged like the columnar structure.

• Journal of Biosystems Engineering
• /
• v.32 no.5
• /
• pp.316-323
• /
• 2007

This study was carried out to obtain the basic data for the development of the solid fuel with investigating the characteristics of mixtures of animal wastes and wasted coal and supply it as an energy resource to agricultural farms for heating of agricultural facilities. It was investigated for the characteristics of animal wastes (swine waste, swine waste with sawdust, cattle waste), wasted coal, the mixtures of animal wastes and wasted coal with or without mixing seawater. The characteristics of solid fuel according to the mixture ratio of animal wastes and wasted coal were analyzed. The effects of seawater affecting on calorific value and thermal pyrolysis of solid fuels were investigated. The results of this study are as follows: 1) The calorific value was improved with mixing seawater into wasted coal due to chemical reaction. 2) The diverse solid fuels of various calorific values can be made with adjusting the ratio of animal wastes and wasted coal. 3) Animal wastes and wasted coal had each different reaction temperature of thermal pyrolysis and the decreasing rate of weight. 4) The mixture of animal wastes and wasted coal would be ignited easily. Therefore, the solid fuel could be ignited more conveniently when seawater is mixed with it.

• Culinary science and hospitality research
• /
• v.14 no.3
• /
• pp.196-209
• /
• 2008

This study was conducted to mass-produce brown stock optimized by using a high-pressure heating extractor and to use brown stock as a material for developing various products. For these purposes, we attempted to produce standardized brown stock by extracting brown stock using a high-pressure heating extractor and compared it with brown stock extracted by the traditional method in terms of general elements and mechanical and sensory characteristics. With regard to how to prepare optimal brown stock, the best brown stock was that extracted seven times repeatedly by the traditional method, but the method had a large economic loss in terms of material consumption and took a long time in extraction. Thus, considering time and labor, it was concluded that extraction at 120$^{\circ}C$ for 15 hours using a high-pressure heating extractor is the optimal extraction condition in terms of economic efficiency and quality. The results of this study are expected to be useful as a practical material for making brown stock production process more convenient, applying cooks' traditional cooking techniques to mass production, maintaining standardized superior quality and taste, and improving shelf life.

• Journal of Magnetics
• /
• v.4 no.4
• /
• pp.123-127
• /
• 1999

The Ga-stabilised $Sm_2Fe_{17-}$type alloy can hardly be disproportionated under ordinary HDDR condition. The HDDR characteristics of Ga-substituted $Sm_2Fe_{17-}$type alloy were examined, and, in particular, the effect of particle size on the disproportionation of the Ga-substituted alloy was investigated in detail. The reaction characteristics of the $Sm_2Fe_{17-}$type alloys with or without Ga-substitution with methane (CH4) gas are also examined. The Ga-stabilised $Sm_2Fe_{17-}$type alloy was able to be disproportionated significantly on heating up to 80$0^{\circ}C$ under hydrogen with normal pressure. The particle size influenced significantly on the disproportion-ation of the Ga-substitute alloy, and the materials with finer particle size (<40 ${\mu}{\textrm}{m}$) was fully disproportionated on heating up to around 80$0^{\circ}C$ under hydrogen gas with normal pressure. The Ga-substituted alloy has a very sluggish recombination kinetics with respect to the alloy without Ga-substitution. The $Sm_2Fe_{17}C_{x-}$type carbide was stabilised significantly by the Ga-substitution for Fe in the parent alloy. While the $Sm_2Fe_{17}C_x$ was disproportionated below 80$0^{\circ}C$ the Ga-stabilised $Sm_2Fe_{14}Ga_2C_x$ carbide remained intact even on heating up to 80$0^{\circ}C$.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.17 no.4
• /
• pp.413-421
• /
• 2014

Since the structural temperature of a flight vehicle flying at high speed rises rapidly due to aerodynamic heating, it is necessary for optimum structural design to obtain proper material properties at high temperature by taking into account of its operational environment. For a special alloy, analysis data on strength change due to exposure time to high temperature are very limited, and most of them are for an exposure time longer than 30 minutes for long term operations. In this study, base and weld metal samples of Ti-6Al-4V alloy had been prepared and high temperature tensile tests with induction heating were performed, and then high temperature strength characteristics and strength recovery characteristics through cooling have been analyzed. Pre-tests to determine maximum heating rate were performed, and response characteristics for temperature control were confirmed. As a result, high temperature tensile strength appeared to be lower than that of room temperature, but it was higher than that of high temperature of 30 minite exposure listed in MMPDS. In strength recovery through cooling Ti-6Al-4V alloy has shown higher recovery rate compared with other alloys.

• Journal of Surface Science and Engineering
• /
• v.52 no.1
• /
• pp.43-51
• /
• 2019

The environmental pollution which is global warming and abnormal climate is caused by increasing population and activated economics. To reduce environmental pollution, we have being efforts into reducing $CO_2$ emission and use of energy, resources. Especially, for the sake of light weight and fuel efficiency of automotive industry, many countries have defined the restrict environmental regulation which stipulate high magnitude of reducing $CO_2$ emission. In this study, we have predicted the problem of Mu-cell injection molding through the finite element analysis as a function of temperature controlled by Joule heating or in terms of mold temperature. From the result of finite element analysis, we have determined the optimized process and made the injection mold included electric current heating system with Mu-cell manufacturing. Lastly, we analyzed the surface characteristics of the injection products with mold temperature.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.17 no.4
• /
• pp.36-45
• /
• 2021

In this study, to improve the indoor thermal environment of the radiant floor heating system, a study was conducted on the temperature change characteristics and energy consumption according to the change of the indoor air set temperature, the supply hot water temperature and the outdoor temperature. As for the control method, the on/off control and the thermal difference proportional control method proposed through previous studies were applied. In addition, in consideration of field applicability, numerical analysis was performed for the case where the indoor air temperature sensor was affected by the wall temperature. As a result, it was found that the temperature difference proportional control method is more effective for thermal comfort and energy saving than on/off control.