• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.122-123
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• 2017

As the building is becomes bigger and larger, it can lead to big damage in case of fire. Also, tunnel, machine room and underground joint are spaces that can cause high temperature fire above 1,350℃ in case of fire. Therefore, a refractory material is need that can be withstand in high temperatures for long time. One side, the composition of oyster shell is CaCO₃ of 90% or more. It is expected that it will be possible to use it as a high calcium natural material which is the material of the refractory board. According to, Study on bending, compressive strength of mortar according to temperature and heating time change using classified oyster shell as aggregate.

• Advances in concrete construction
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• 제5권5호
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• pp.513-537
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• 2017

In this study, the fracture toughness $K_{IC}$ of high performance concrete (HPC) was investigated by conducting three-point bending tests on a total of 240 notched beams of $500mm{\times}100mm{\times}100mm$ subjected to heating temperatures up to $450^{\circ}C$ with exposure times up to 16 hours and various heating and cooling rates. For a heating rate of $3^{\circ}C/min$, $K_{IC}$ for the hot concrete sustained a monotonic decrease trend with the increasing heating temperature and exposure time, from $1.389MN/m^{1.5}$ at room temperature to $0.942MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.906MN/m^{1.5}$ for 8-hour exposure time and $0.866MN/m^{1.5}$ for 16-hour exposure time. For the cold concrete, $K_{IC}$ sustained a two-stage decrease trend, dropping slowly with the heating temperature up to $150^{\circ}C$ and then rapidly down to $0.869MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.812MN/m^{1.5}$ for 8-hour exposure time and $0.771MN/m^{1.5}$ for 16-hour exposure time. In general, the $K_{IC}$ values for the hot concrete up to $200^{\circ}C$ were larger than those for the cold concrete, and an inverse trend was observed thereafter. The increase in heating rate slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.893MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.839MN/m^{1.5}$ for $10^{\circ}C/min$ for the hot concrete and from $0.792MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.743MN/m^{1.5}$ for $10^{\circ}C/min$ for the cold concrete after an exposure time of 16 hours. The increase in cooling rate also slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.771MN/m^{1.5}$ for slow cooling to $0.739MN/m^{1.5}$ for fast cooling after an exposure time of 16 hours. The fracture energy-based fracture toughness $K_{IC}$' was also assessed, and similar decrease trends with the heating temperature and exposure time existed for both hot and cold concretes. The relationships of two fracture toughness parameters with the weight loss and the modulus of rapture were also evaluated.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.136.1-136.1
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• 2011

This paper proposes the method to implement the railroad switching point heating system using the hybrid of the photovoltaic and wind power. The goal of the implementation of the railroad switching point heating system is to prevent freezing of the snow in the winter. The heating system of railway used to supply electricity through photovoltaic and wind power to prevent freezing. Hot wires of the railroad switching point heating system are used about 2kW of electric energy at the day. The electric energy of 2kW used the length of the hot wires about 3m. As the ON and/or OFF mode considering the tracks temperature and the ambient temperature, so the way the use of power-saving effect. In addition, the system can be used the railroad switching point heating system in winter and railway signal and street lights around the track in summer. In experiment, we acquired the power data according to time at the day of photovoltaic and wind power. We confirmed the temperature rise using the heating cable for 3m of $85^{\circ}C$, 30W/m. The temperature rise of the heating cable changes the temperature of $5^{\circ}C$ after 10 minutes and $11^{\circ}C$ after 10 minutes. We have confirmed the possibility of the railroad switching point heating system using the hybrid of the photovoltaic and wind power.

• 소성∙가공
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• 제31권2호
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• pp.96-102
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• 2022

The multi-point dieless forming technology is one of flexible forming technologies that can form 3D curved surfaces of various shapes utilizing a lot of punch arrangements. A new technology that can simultaneously apply high-temperature forming and flexible forming technology by fusing local heating effect to such multi-point dieless forming technology was proposed in the present study. A simple local heating multi-point dieless forming apparatus was fabricated to confirm the applicability of this new technology. This equipment was designed to be used as a heat source by inserting heating cartridges in the head of the multi-point punch. Cartridges were used for all individual punches. Using the manufactured equipment, the time to raise the temperature to the target temperature and the surface temperature of the punch head part in contact with the plate were measured. In addition, forming experiments were carried out according to sheet material temperature (100 ℃, 200 ℃, and 300 ℃) to obtain forming results for each condition. The applicability and feasibility of this technology were confirmed through experimental results.

• 설비공학논문집
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• 제11권4호
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• pp.528-536
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• 1999

This work studies the effects of transient reflectance on the thermal responses of a metal(gold) thin-film during ultrashort laser heating. The heating process is calculated using the conventional conduction model (parabolic one-step: POS), parabolic two-step model (PTS) with and without variable properties, hyperbolic two-step model (HTS). Results from the HTS model are very similar to those from the PTS model, since the laser heating time in this study is greater than the electron relaxation time. PTS model with variable properties, however, results in totally different temperature profiles compared to those from POS models or calculation with constant properties. Transient reflectances are estimated from electron temperature distributions and based on the linear relationship between the electron temperature and complex dielectric constants. Reflectance of the front surface can be changed with respect to dielectric constants, while those of the rear surface remain unchanged.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권1호
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• pp.1-9
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• 2002

Effects of temperature coefficients fur dielectric constants on transient reflectances and thermal responses have been investigated for a metal(gold) thin-film during ultrashort pulse laser heating. Heating processes are simulated using the conventional conduction model(parabolic one-step, POS), the parabolic tow-step model(PTS), the hyperbolic two-step model(HTS). Results fro the HTS model are very similar to those from the PTS model, since the laser heating time in this study is considerably greater than the electron relaxation time. PTS and HTS models, however, result in completely different temperature profiles from those obtained by the POS model due to slow electron-lattice interactions compared to laser pulse duration. Transient reflectances are directly estimated from the linear relationship between electron temperature and complex dielectric constants, while conventional approaches assume that the change in reflectances is proportional to that in temperatuer. Reflectances at the front surface vary considerably for various dielectric constants, while those at the rear surface remain unchanged relatively.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1095-1100
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• 2006

An experimental study has been performed to investigate the correlation on compressor discharge temperature of system A/C in heating mode. Indoor and outdoor temperatures, the heating capacity, compressor discharge temperature and loading time are measured by the psychrometric calorimeter. The system is controlled by applying the scroll compressor, which Is operated by PWM valve and loading duty. With increasing outdoor temperature, the heating capacity increases, With increasing indoor temperature, it decreases. Also, with increasing loading duty the heating capacity increases. According to the increase in outdoor temperature and loading duty, compressor discharge temperature increases. From these experimental data, the correlation on compressor discharge temperature is proposed. It is expressed as a function of indoor temperature, outdoor temperature, and loading duty. The correlation obtained from the present study is agreed with the experimental data within $2^{\circ}C$.

• Journal of Biosystems Engineering
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• 제31권6호
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• pp.529-534
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• 2006

The greenhouse heating system with far-infrared heater was built to analyze various thermal characteristics, such as greenhouse air temperature, soil temperature, energy flow, energy consumption in far-infrared heater, and other factors, which could be used in comparison with other greenhouse heating system in this study. The results showed that the inside air temperature of the far-infrared greenhouse heating system was $5^{\circ}C$ higher than that of hot air heating system. Heat loss of daytime was found to be larger than that of night time as much as 44.8% for the heating system with far-infrared heater. In the heating system with far-Infrared heater, when the lowest ambient temperature was -8 $\sim$ -7$^{\circ}C$, the air temperature of greenhouse was 12 $\sim$ 15$^{\circ}C$, thus the far-infrared heating system was shown to be feasible for heating system. Energy consumption of far-infrared heating system was shown to be less than that of hot air heating system.

• 한국가금학회지
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• 제17권2호
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• pp.127-133
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• 1990

가열온도와 시간, pH 및 NaCl 농도가 난백겔의 열안정성에 미치는 영향을 검토하기 위하여 가열처리 후 난백겔의 특성을 검토하였으며 그 결과는 다음과 같다. 난백을 90~$170^{\circ}C$까지 온도와 시간별 가열처리 한 결과. 110~$130^{\circ}C$ 영역에서 경도가 떨어졌으나 온도가 높아짐에 따라서 급격히 증가하였다. 응집성의 경우는 12$0^{\circ}C$까지 감소한 후 $130^{\circ}C$에서 급격히 증가하였다. 명도는 온도가 높아질수록 시간이 길어질수록 낮아졌으며 황색도는 높아졌다. 난백의 경도는 pH 7을 중심으로 산성영역에서는 고온처리가 높았으며 알카리영역에서 밝았다. 고온처리의 경우가 저온처리에 비해 산성영역에서는 보다 밝았으며 알카리 영역에서는 보다 어두웠다. 염의 첨가에 의해 난백의 경도는 저온처리 시에는 큰 변화가 없었으나 고온처리시 다소 증가하였고 응고집성은 저온처리시 서서히 증가하였으며 고온처리시 0.5%까지 급격히 증가하였다. 색택은 고온고리시 명도가 증가하였고 황색도는 감소하였으며 농도별 차이는 크지 않았다.

• 한국군사과학기술학회지
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• 제17권4호
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• pp.413-421
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• 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.