• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.476-482
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• 2019

Regulatory protocols such as the Convention on Climate Change and the regulation of greenhouse gas emissions act as catalysts for the development of high-efficiency energy equipment and the efficient use of energy. Among the fields where energy consumption is high, the electric heating equipment is not efficient. The electric boiler mainly uses a method of circulating water by contacting the heater. When the existing electric boiler is used, the water minerals are contacted with the high-temperature heater to be carbonized and adsorbed, thereby promoting the corrosion of the heater and lowering the efficiency of the heater. For this reason, an electric induction boiler, which has high energy efficiency and is applied to an induction heating system that can uniformly heat the object to be heated rather than conduction or convection heating, is in the limelight. This method induces a boiler pipe And it is recognized as an alternative that can solve the problem that occurs when heating is performed by direct heating. Despite the fact that research on induction heating has been conducted for a relatively long period of time, there have been few studies on the electrothermal technology using induction heating. Therefore, in this paper, to improve the heat efficiency of electric induction boiler, the influence of the cross sectional area, number of windings and winding layers is analyzed by finite element method through parametric study method. The method of finding the design point which maximizes the total loss is proposed by the alternating winding design method which can maximize the heat generation by analyzing copper and iron losses.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.69-69
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• 2011

태양열 발전 플랜트에 사용되는 중고온 범위의 축열조에 고체-액체간 상변화를 수행하는 용융염을 축열물질로 사용하면 액체상 또는 고체상만으로 된 열저장 매체에 비해 축열조의 규모를 축소함과 동시에 축열온도의 균일성 향상에 기여할 수 있다. 중온인 $250{\sim}400^{\circ}C$ 범위에서 이용 가능한 용융염으로는 질산칼륨($KNO_3$), 질산리튬($LiNO_3$)등이 있다. 그러나 이러한 용융염의 가장 큰 단점은 열전도율이 매우 낮다는 것이며, 이로 인해 요구되는 열전달률을 성취하기 위해서는 많은 열접촉면적이 필요하다는 것이다. 이러한 단점을 극복하는 방법을 도입하지 않고서는 축열시스템의 소규화를 성취하는데 큰 효과를 가져올 수 없다. 한편 열수송 성능이 탁월한 히트파이프를 사용하면 열원 및 열침과 축열물질 사이의 열전달 효율을 증가시켜 시스템의 성능 향상과 동시에 소규모화에 기여할 수 있다. 중온 범위 히트파이프의 작동유체로서 다우섬-A(Dowtherm-A)는 $150^{\circ}C$이상 $400^{\circ}C$까지의 범위에서 소수에 불과한 선택적 대안 중 하나이다. 따라서 본 연구에서는 용융염을 사용하는 중온 태양열축열조에 적용 가능한 다우섬-A 히트파이프의 성능을 파악하여 기술적 자료를 제시하고자 하였다. 열원으로는 고온 고압의 과열증기, 그리고 열침으로는 중온의 포화증기를 고려하였다. 용융염 축열조를 수직으로 관통하는 히트파이프는 하단부에서 열원 증기와 열교환 가능하며, 중앙부에서 축열물질과 열교환하고, 상단부에서는 중온 증기와 접촉할 수 있도록 배치하였다. 축열모드에서는 히트파이프의 하단부가 증발부로 작동하고, 중앙부가 응축부로 작동하여 용융염으로 열을 방출하면 용융염의 온도가 상승하고 용융점에 도달하면 액상으로의 상변화가 진행되면서 축열이 활성화된다. 축열모드에서 히트파이프의 상단부는 단열부로 작동한다. 방열과정에서는 히트파이프의 하단부가 단열된 상태이고, 중앙부는 용융염으로부터 열을 받아 증발부로 작동하며, 상단부는 중온 증기로 열을 방출하므로 응축부로 작동한다. 즉, 축열시스템의 작동모드에 따라 하나의 히트파이프에서 증발부, 응축부, 단열부의 위치가 변하게 된다. 특히, 히트파이프의 중앙 부분이 응축부에서 증발부로 전환될 때에도 작동이 보장되려면 내부 작동유체의 연속적인 재순환이 가능해야 하므로, 일반 히트파이프에서와는 달리 초기 작동액체의 충전량을 증발부 전체의 체적보다 더 많이 과충전해야 한다. 이러한 히트파이프의 성능 파악을 위한 실험에서 고려한 변수들은 열부하, 작동액체의 충전률, 작동온도 등이며, 열수송 성능의 지표로서는 유효열전도율과 열저항을 이용하였다. 중온범위에서 적정한 작동온도를 성취하기 위해 실험에서는 전압 조절기로 열부하를 조절하는 동시에 항온조로 응축부의 냉각수 입구 온도를 제어하였다. 하나의 히트파이프에 대해서 최대 1 kW까지의 열부하에서 냉각수 입구 온도를 $40^{\circ}C$에서 $80^{\circ}C$ 범위로 변화시키면 히트파이프 작동온도를 약 $250^{\circ}C$ 내외로 조절 가능하였다. 히트파이프 작동액체 충전률은 윅구조물의 공극 체적을 기준으로 372%에서 420%까지 변화 시켰다. 실험 결과를 토대로 열저항과 유효 열전도율을 각각 입력 열유속, 작동온도, 작동액체 충전률 등의 함수로 제시했다. 동일한 냉각수 온도에서는 충전률이 높을수록 히트파이프의 작동온도가 감소하였다. 열저항 값의 범위는 최소 $0.12^{\circ}C/W$에서 최대 $0.15^{\circ}C/W$까지로 나타났으며 유효 열전도율의 값은 최소 $7,703W/m{\cdot}K$에서 최대 $8,890W/m{\cdot}K$까지 변화했다. 최소 열저항은 충전률 420%인 경우에 나타났는데 이때의 작동온도는 약 $262^{\circ}C$이었다. 히트파이프의 작동한계로서 드라이아웃(dry-out)은 충전률 372%의 경우에 열부하 950 W에서 발생하였으나, 그 이상의 충전률에서는 열부하 1060 W까지 작동한계 발생이 관찰되지 않았다. 실험 결과 본 연구에서의 히트파이프는 중온 태양열 축열조에 적용되어 개당 약 1 kW의 열부하를 이송하면서 축열물질 및 축방열 대상 유동매체와 열교환을 하는데 사용하는데 충분할 것이라 판단된다.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.503-513
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• 2006

Statement of the problem: The cold-cured resins used in fabrication of the provisional crown and fixed partial dentures could cause pulpal damage by heat generated during exothermic polymerization reactions. Purpose: In this in vitro study investigates the how external conditions such as material of the matrix, thickness of the matrix and thickness of dentin affect the temperature of the tooth during polymerization reaction of the cold-cured resins. Material and methods : To measure the temperature of the resin, metal die was maintained to the temperature of $37^{\circ}C$ with water bath to simulate the temperature of thetooth and thermocouple was placed in the center of the metal die. Acrylic pipe was cut in height of 1, 2, 3, 6, 10 mm and placed on the metal die and mixed resin was pored in the acrylic pipe As the resin polymerized temperature was recorded with the thermometer. Temperature of the resin using matrix was recorded by using the individual tray relieved in different thickness 2, 5, 7, 10 mm. The material of the matrix was irreversible hydrocolloid impression material, vinyl polysilloxane impression material and vacuum-formed template Temperature rise of the resin using different thickness of tooth section was record ed by placing tooth section on the metal die and placing resin over the tooth section. Results : Conclusion : 1. Temperature rise increased as the thickness of the resin increased but there was no significant differences over 3 mm thickness of the resin. 2. The lowest temperature rise was showed in irreversible hydrocolloid impression material and vinyl polysilloxane impression material vacuum-formed template as in orders. 3, Temperature rise of the resin decreased regardless of the thickness of the matrix when vinyl polysilloxane impression material was used as the matrix. 4 When irreversible hydrocolloid impression material was used as matrix, the temperature rise of the resin decreased as the thickness of the matrix increased and there was no temperature rise when thickness of the matrix reached 10 mm, 5. The temperature rise of the resin did not decreased when Polypropylene vacuum-formed template was used as the matrix. 6, The temperature of the resin increased as the thickness of the dentin decreased.

• Journal of Korea Water Resources Association
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• v.49 no.9
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• pp.799-807
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• 2016

The aim of this study is to determine and propose the by-pass rainwater sewer system in order to reduce the urban floodplain from the locality heavy rain every year during the dry season and the sinkholes in the city as well as the shortage of groundwaters due to extreme hot weather condition and urban heat island phenomenon. Heavy rain occurs more than the years of heavy rainfall probability, comparison between the place where uses the existing pipes and connect the sewer system with by-pass rain permeability and without expanding sewer pipe replacement at intersection of Gangnam station 3.07 ha at Gangnam-gu, Seoul Metropolitan area, it indicates that average of 27 million KRW (44%) maintenance cost savings and maintain existing sewer system without any other countermeasures. For the city flooded reduction, by-pass rainwater permeable rainwater pipe multiplying the probability the number of years during summer season and increase the water flow capacity during spring and fall when a small amount of rain that, it also contribute to the total amount of underground water secured through the by-pass penetration.

• Composites Research
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• v.37 no.3
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• pp.238-245
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• 2024

In this study, as part of the development of a monitoring system for the efficient maintenance of steel pipes, an experimental study was conducted to evaluate the performance of steel pipes treated with modified polyethylene coating. In the case of the conventional mechanical pre-coating method, there was a deterioration in polyethylene adhesion during expansion testing, which led to the application of a chemical pre-treatment process using a calcium-mixed phosphate zinc film to resolve this issue. SEM and EDX analyses showed that the densest structure was observed at a Zn/Ca ratio of 1.0, and improved heat resistance compared to the conventional method was confirmed. Additionally, to prevent coating detachment during expansion, an evaluation of adhesion and elongation was conducted on steel pipes with modified polyethylene coating, incorporating materials such as elastomers based on maleic anhydride grafting, metal oxides, blocking agents, and slip agents. Experimental results showed that the specimen (S4) containing all modified materials exhibited more than a 25% performance improvement compared to the specimen (S2) containing only metal oxides. Lastly, the development and performance evaluation of wedge-shaped socketing and pressing wheels, which are part of the pipe fixing accessories, were conducted to prevent surface coating damage on the completed pipes.

• Journal of Bio-Environment Control
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• v.30 no.4
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• pp.278-286
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• 2021

In this study, based on the Computational Fluid Dynamics (CFD) simulation model developed through previous study, inner environmenct of the modified glass greenhouse was predicted. Also, suggested the optimal shape of the greenhouse and location of the heat exchangers for heat energy management of the greenhouse using the developed model. For efficient heating energy management, the glass greenhouse was modified by changing the cross-section design and the location of the heat exchanger. The optimal cross-section design was selected based on the cross-section design standard of Republic of Korea's glass greenhouse, and the Fan Coil Unit(FCU) and the radiating pipe were re-positioned based on "Standard of greenhouse environment design" to enhance energy saving efficiency. The simulation analysis was performed to predict the inner temperature distribution and heat transfer with the modified greenhouse structure using the developed inner environment prediction model. As a result of simulation, the mean temperature and uniformity of the modified greenhouse were 0.65℃, 0.75%p higher than those of the control greenhouse, respectively. Also, the maximum deviation decreased by an average of 0.25℃. And the mean age of air was 18 sec. lower than that of the control greenhouse. It was confirmed that efficient heating energy management was possible in the modified greenhouse, when considered the temperature uniformity and the ventilation performance.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.477-484
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• 2009

It is important for the strategy of service to provide the weather information in the environment that the smart clothing has been changed focusing on the consumer center. Recently, the various applications of smart clothing concept have been presented by researchers and developers. Among them, the smart clothing based on the sensors is most likely to gain the highest demand rate in the market. In this paper, we proposed the life weather index monitoring system using the wearable based smart cap. By wearing the proposed smart cap, the weather status is gathered and its signals are transmitted to the connected UMPC. It can be easily monitored in real time. To provide the life weather index according to the sensors, the weather index was analyzed in terms of 6 factors, such as, the heat index, the food poisoning index, the discomfort index, the ultraviolet index, the water pipe freeze possibility index, and the windchill temperature index. Ultimately, this paper suggests empirical application to verify the adequacy and the validity with the life weather index monitoring system. Accordingly, the satisfaction and the quality of services will be improved the smart clothing.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.2
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• pp.67-87
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• 1991

The computer program which predicts the gas exchange process of multi-cylinder 4-Stroke cycle spark-ignition engine, can be great assistance for the design and development of new engine. In this study, the computer program was developed to predict the gas exchange process of multi-cylinder four stroke cycle spark ignition engine including intake and exhaust systems. When gas exchange process is to be calculated, the evaluation of the variation of the thermo-dynamic properties with time and position in the intake and exhaust systems is required. For the purpose, the application of the generalized method of characteristics to the gas exchange process is known as one of the method. The simulation model developed was investigated to the analysis of the branch system of multi-cylinder. The models used were the 2-zone expansion model and single zone model for in cylinder calculation and the generalized method of characteristic including area change, friction, heat transfer and entropy gradients for pipe flow calculation. The empirical constants reduced to least number as possible were determined through the comparison with the experimented indicator diagram of one particular operation condition and these constants were applied to other operating condition. The predicted pressures in cylinder were compared with the experimental results over the wide range of equivalence ratio and ignition timing. The predicted values have shown good agreement with the experimental results. The thermodynamic properties in the intake and exhaust system were predicted over the wide range of equivalence ratio and ignition timing. The obtained results can be summarized as follows. 1. Pressures in the exhaust manifold have a little influence on the equivalence ratio, a great influence on the ignition timing. 2. Pressures in the inlet manifold are nearly unchanged by the equivalence ratio and the ignition timing. 3. In this study, the behaviors of the exhaust temperature, gas in the exhaust manifold were ascertained.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.129.1-129.1
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• 2016

반도체, 디스플레이, PC 등 전자기기의 경우 소자 내 발생된 열로 인해 기기의 성능 및 효율, 수명 등이 감소하기 때문에 이러한 내부 열을 외부로 방출시켜줄 필요가 있다. 일반적으로 heat pipe나 냉각 팬(fan) 등의 외부장치에 의해 강제적으로 냉각해주는 기술이 있지만 휴대용 디바이스와 같이 작은 전자기기의 경우 소자 자체적으로 열전도 특성이 뛰어난 기판을 사용하여 열전도에 의해 열이 소자 밖으로 방출될 수 있도록 방열 설계를 해주어야 한다. 따라서 소자 전체를 지지해주고 열전도에 의해 방열 기능을 해주는 방열기판에 대한 관심이 증가하고 있다. 현재 가장 많이 사용되어지는 세라믹 방열기판으로는 알루미나가 있지만 보다 소자의 집적화와 고성능화로 인하여 열전도도가 높은 질화규소 기판의 요구가 증대되고 있다. 하지만 이러한 질화규소기판에 금속전극을 형성하는 기술은 종래의 알루미나 기판에 이용한 DPC(Direct Plated Copper), DBC(Direct Bonded Copper)기술을 적용할 수 없다. 그래서 현재는 메탈블레이징을 이용하여 전극을 형성하지만 공정비용 및 대형기판에 형성이 어려운 단점이 있다. 따라서, 본 연구에서는 질화규소 방열기판에 전기화학공정을 통하여 밀착력이 우수한 금속 전극 회로층 형성에 대한 연구를 진행하였다. 질화규소 방열기판에 무전해 Ni 도금을 통하여 금속층을 형성하는데 이 때 세라믹 기판과 금속층 사이의 낮은 밀착력을 향상시키기 위해 습식공정을 통하여 표면처리를 진행하였다. 또한 촉매층을 $Pd-TiO_2$ 층을 이용하여 무전해 도금공정을 이용하여 Ni, 전극층을 형성하였다. 질화규소 표면에 OH기 형성을 확인하기 위해 FT-IR(Fourier-transform infrared spectroscopy)분석을 실시하였으며 OH 그룹 형성 및 silane의 화학적 결합으로 인해 금속 전극층의 밀착력이 향상된 것을 cross hatch test 및 scratch test를 통해 확인하였고 계면 및 표면형상 특성 등을 분석하기 위해 TEM(Transmission electron microscopy), SEM(Scanning electron microscopy), AFM(Atomic-force microscopy)등의 장비를 이용하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.578-584
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• 2013

Ice slurry that is a mixture of fine ice crystals and liquid water is a widely used working fluid in the ice thermal energy storage system due to its flowability and large latent heat of fusion. Generally ice slurry is made from supercooled water. But the excessive supercooling causes the water to freeze even worse to block the pipe. Additionally large degree of supercooling of water degrades the efficiency of the ice thermal energy storage system. Therefore the effective method to control the phase change from supercooled water to ice slurry is needed. In this paper we experimentally studied a novel method to generate the ice slurry from the supercooled water using the ultrasonic vibration. It was found that the cavitation impact of supercooled water by ultrasonic vibration can help the generation of ice slurry.