• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.570-575
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• 2007

The thermal performance of the air receiver filled with porous material for 5kWt dish solar collector installed in Inha University, Korea, is experimentally investigated. The diameter of the parabolic dish is 3.2 m, and its focal length is 2 m. It consists of 10 small pieces of glasses which have their own curvatures, and the effective reflecting area is 5.9 m2. The reflectivity of the glass is 0.95, and the thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. A quartz window is installed at the receiver aperture to minimize the convective heat loss and prevent air leakages. In order to increase the heat transfer area, porous material (nickel-alloy) is inserted into the receiver. Air flows into the upper part of the receiver, which is the opposite side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 3 exits which are located near the aperture. The volumetric flow rates of air are varied from 600 to 1200 L/min. The thermal efficiency of the receiver ranges from 82% - 92% depending upon the flow rate. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases as expected. These results from the experiment will be useful for the applications to air heating receivers and solar reactors.

• Journal of Advanced Marine Engineering and Technology
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• 제33권8호
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• pp.1129-1136
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• 2009

본 논문은 EEV를 이용한 냉각시스템의 성능특성에 관한 논문이다. 산업용냉각기는 고속으로 운전하는 공작기기의 열 변형을 줄이기 위해 사용되었으며, EEV는 냉각기의 용량조절을 위해 사용되었다. 본 장치는 압축기 출구에서 나온 핫가스를 증발기 입구로 보내는 핫가스 바이패스 시스템을 위해 설계되었다. 본 실험은 PID제어를 통한 고정도 온도제어 연구의 중간결과물이다. 실험의 결과로 핫가스 바이패스의 EEV스텝 조절을 통하여 증발압력의 상승과 냉동능력의 감소를 알 수 있었다. 본 실험의 결과를 통하여 효율적인 냉각기의 설계에 있어 기초 자료로 이용할 예정이다.

• 조명전기설비학회논문지
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• 제30권2호
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• pp.71-77
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• 2016

The dielectric barrier discharge (DBD) has low efficiency due to about 70% input power is consumed as thermal energy in the discharge space. However, because of the usage of DBD ozone generator is easier than other methods. The DBD ozone generator has been widely applied for high concentration ozone generation in the industrial application. But, the low-capacity compact DBD ozone generator is not applied so far. Therefore, the DBD ozone generator is necessary to improve ozone production efficiency and reduce the capacity. In this paper, the stainless steel pipe inner electrode was designed with hall type and screw type to improve the ozone production yield. The manufactured two inner electrodes were experimented with normal type for comparison of the discharge characteristics and the ozone generating characteristics. As the experimental results, the discharge current effective value of designed inner electrodes with hall type and screw type are higher than the normal type, due to unequal electric field is formed at the boundary. However, the difference of designed and original electrodes is less than 0.1mA that has no effect on the discharge characteristic. On the other hand, the screw type inner electrode increased higher than original model about 7 times when the flow rate of the oxygen source gas was increased from $0.6{\ell}/min$ to $1.0{\ell}/min$ The reason was assumed by the flow rate of the raw gas through the inner electrode was became fast that has a cooling effect. The designed hall type and screw type inner electrodes have shown good performances in ozone generation and ozone production that better than normal type in the same electrode surface area.

• 한국구조물진단유지관리공학회 논문집
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• 제18권5호
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• pp.51-58
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• 2014

본 연구에서는 철근콘크리트 구조의 FRP를 이용한 보강에서 낮은 내화성능을 개선하기 위한 방안을 찾기 위하여, 보강된 FRP의 외부를 내화보강하는 방법에 대한 내화실험을 실시하였다. 특히 철근콘크리트 부재의 피복에 홈을 형성하여 FRP를 매입하는 보강 즉, NSM 보강을 대상으로 하였다. 실험에서의 주요 변수는 보강방법과 사용 내화재료로서, Perlite계 재료를 표면에 분사하여 보강하는 방법, Calcium silicate계 보드로 표면에 부착하는 방법, 그리고 추가로 홈내부에 Polymer mortar 또는 Calcium silicate조각을 삽입하여 보강하는 방법으로 보강한 뒤 가열로 내부의 온도변화에 따른 열전달을 관찰하였다. 실험결과, Perlite계 내화뿜칠로 표면을 보강하는 경우보다 Calcium Silicate계 내화보드로 표면을 보강하는 방법이 효과적인 것으로 나타났다. 홈 내부의 에폭시가 유리전이온도에 도달할 때의 외부 표면온도 $820^{\circ}C$까지 내화단열성능을 확보할 수 있는 것으로 나타났다.

• 한국산학기술학회논문지
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• 제17권1호
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• pp.591-596
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• 2016

굴뚝의 백연을 줄이기 위하여 6종의 전열판을 선정하여 각각에 대한 열유동 특성을 연구하였다. 본 연구에서는 전열판의 열전달 성능(열전달 능력, 압력강하, 난류운동 에너지, 열전달계수 등)을 조사하기 위하여 상용 전산유체역학 프로그램인 ANSYS CFX Ver.14를 활용하여 균일유동 조건에서 수치해석을 수행하였다, 다른 유로구조를 가지는 6종의 전열판에 대한 전산해석으로부터 기본형, 사각형, 삼각형, 파형 열교환기의 열유동 과정이 모사되었다. 균일유동 해석으로부터 6종 열교환기들의 열전달 능력, 압력강하, 난류운동 에너지, 열전달계수들은 다른 경향을 보였으며, 유로 내의 열유동 특성은 주어진 유량, 전열판 형상, 종횡비에 좌우됨을 알 수 있었으며, 동일 파형에서는 종횡비가 낮을수록 열전달 성능이 우수하였다. 본 연구의 결과는 백연저감용 열교환기의 설계 기초자료로 활용될 것이다.

• 한국가스학회지
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• 제17권5호
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• pp.8-14
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• 2013

천연가스에 수소를 첨가하는 수소-천연가스 혼합연료 (HCNG) 엔진 기술은 수소의 빠른 화염속도와 넓은 가연범위를 이용하여 출력 및 배기성능을 최적화하는 기술로서 희박연소 한계를 증가시킴으로써 열효율의 개선은 물론 유해배출물의 저감을 얻을 수 있다. 그러나 과급장치를 사용하는 희박연소 엔진의 경우 전부하 운전조건에서 희박연소 한계의 증가는 충분한 공기량을 공급할 수 있도록 과급용량의 증가가 선결되어야 구현될 수 있다. 본 연구에서는 HCNG 엔진 개발의 일환으로 과급시스템의 변경에 의한 엔진의 출력특성을 파악하고, 과급용량 증대의 적용가능성을 검토하고자 하였다. 터보차저가 과급압력의 증대 보다는 유량이 증가된 영역에서 효율이 높게 설계된 경우 농후한 혼합기 조건에서는 과급압력이 감소되더라도 제원상의 출력을 만족하며 효율적인 운전이 가능하였다.

• 설비공학논문집
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• 제28권11호
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• pp.421-427
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• 2016

The indoor temperature of a building increases during the day due to solar radiation. This behavior is significant in school buildings that are finished with high thermal capacity materials. Moreover, in school buildings, windows cannot be opened until the class has finished owing to the security policy of schools. Consequently, classrooms maintain a high temperature throughout the morning. It is thus important to remove the indoor heat before the commencement of classes in order to reduce the cooling energy needed. The Energy Recovery Ventilator (ERV) system is currently being installed in school buildings for ventilating the classrooms. Night-purge control using ERV can be a good strategy to cool the classroom in advance of the operation of the cooling system. However, the optimal operation method of the ERV for night-purge control has not yet been reported. In this study, the effect of night-purge control with ERV in school buildings is analyzed by simulation method. The results of this study showed that the energy saving effect of night-purge control with ERV is most effective in the case of 2 hours operation prior to the commencement of the first lass and when enthalpy based outdoor air cooling is used.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.240-244
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• 2001

Recycling process involving mechanical, thermal, hydrometallurgical, and sol-gel step has been applied to recover cobalt and lithium from spent lithium ion batteries and to synthesize LiCoO$_2$from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt could be concentrated with 2-step thermal and mechanical treatment. Leaching behaviors of the lithium and cobalt in nitric acid media was investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO$_3$solution turned out to be an effective reducing agent by enhancing the leaching efficiency. O f many possible processes to produce LiCoO$_2$, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO$_2$with nitric acid, the molar ratio of Li/Co in the leach liquor was adjusted at 1.1 by adding a fresh LiNO$_3$solution. Then, 1 M citric acid solution at a 100% stoichiometry was also added to prepare a gelatinous precursor. When the precursor was calcined at 95$0^{\circ}C$ for 24 hr, purely crystalline LiCoO$_2$was successfully obtained. The particle size and specific surface area of the resulting crystalline powders were 20 пm and 30 $\textrm{cm}^2$/g, respectively The LiCoO$_2$powder was proved to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.113-120
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• 2007

The 5kWt dish solar collector is designed and the preliminary performance test for this is carried out. The diameter of the parabolic dish is 3.2 m, and its focal length is 2 m. It consists of 10 small reflectors which have their own curvatures, and the effective reflecting area is $5.9\;m^2$, and the rim angle of the dish is $43.85^{\circ}$. The reflectivity of reflectors is 0.95, and the thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. A quartz window is installed at the receiver aperture to minimize the convective heat loss and prevent air leakage. In order to increase the heat transfer area, porous materials (nickel-alloy) are inserted into the receiver. Air flows into the upper part of the receiver which is the opposite side of the aperture. After the air flows through the inside of the receiver, that goes out of the receiver through 3 exits which are located near the aperture. The volumetric flow rates of air are varied from 600 to 1200 L/min. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases.

• 한국생산제조학회지
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• 제19권1호
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• pp.57-64
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• 2010

Metal Injection Molding (MIM) is attractive because it produces consistent, complex-geometry components for high-volume, high-strength, and high-performance applications. Also MIM using in optical communication field, display field, and semi-conductor field is a cost-effective alternative to metal machining or investment casting parts. It offers tremendous single-step parts consolidation potential and design flexibility. The objective of this paper is to study the suitability of design, flow analysis, debinding and sinterin processes, and capability analysis. The suitable injection conditions were 0.5~1.5 second filling time, 11.0~12.5 MPa injection pressure derived from flow analysis. The gravity of the product is measured after debinding an sintering. The maximum and minimum gravity levels are 7.5939 and 7.5097. the average and standard deviation are 7.5579 and 0.0122; when converted into density, the figure stands at 98.154%. According to an analysis of overall capacity, PPM total, which refers to defect per million opportunities(DPMO), stands at 166,066.3 Z.Bench-the sum of defect rates exceeding the actual lowest and highest limits-is 0.97, which translates into the good quality rate of around 88.4% and the sigma level of 2.47.