• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.237.1-237.1
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• 2010

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Ocean contains energy in form of thermal energy and mechanical energy: thermal energy from solar radiation and mechanical energy from the waves and tides. The current paper looks at generating power using waves. The primary objective of the present study is to maximize the primary energy conversion (first stage conversion) of the base model by making some design changes. The model entire consisted of a numerical wave tank and the turbine section. The turbine section had three components; front guide nozzle, augmentation channel and the rear chamber. The augmentation channel further consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. Different front guide nozzle configuration and rear chamber design were studied. As mentioned, a numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank inlet. The inlet which was modeled as a plate wall which moved sinusoidally with the general function, $x=asin{\omega}t$. In addition to primary energy conversion, observation of flow characteristics, pressure and the velocity in the augmentation channel, rear chamber as well as the front guide nozzle are presented in the paper. The analysis was performed using the commercial code of the ANSYS-CFX. The base model recorded water power of 29.9 W. After making the changes, the best model obtained water power of 37.1 W which represents an increase of approximately 24% in water power and primary energy conversion.

• 한국해양학회지:바다
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• 제3권1호
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• pp.1-8
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• 1998

하계에 연안혼합역과 외해성층역 사이에서 강력한 표층수온전선이 형성되는 한국 서해 중부의 태안반도 인근해역에서 1994년 7월, 1995년 5원 및 1996년 6월 등 3회에 걸쳐 취득한 해수물성자료를 분석하였다. 수직혼합역은 최저 15 m에서 최고 60 m 이상까지의 다양한 수심의 지형으로 이루어졌으며, 수심에 관계없이 표층과 저층의 수온차가 $1^{\circ}C$ 이내였다. 관측시기에 관계없이 혼합역 내의 수평적인 표층수온차는 작으면서도 수심에 반비례하는 특정을 보이고 표층수온이 가장 낮은 해역은 태안반도 서단에서 남서방향으로 형성되어있는 수심이 50 m 이상인 깊은 수로를 중심으로 관측되었다. 또한 6월에 관측한 표층수온전선이 태양복사열이 더 강한 7월에 관측한 표층수온전선에 비해 더 강한 특성을 보였다. 이러한 관측결과는 연구해역의 표층수온전선역은 수층의 수직혼합에 의해 형성되지만, 수온전선의 강도는 수직혼합역의 수성 및 외해성층역의 수온의 수직구조 등에 의해 결정되는 것으로 해석된다.

• 비파괴검사학회지
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• 제35권6호
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• pp.398-406
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• 2015

This paper explored the results of experimental investigation on carbon fiber reinforced polymer (CFRP) composite sample with thermal wave technique. The thermal wave technique combines the advantages of both conventional thermal wave measurement and thermography using a commercial Infrared camera. The sample comprises the artificial inclusions of foreign material to simulate defects of different shape and size at different depths. Lock-in thermography is employed for the detection of defects. The temperature field of the front surface of sample was observed and analysed at several excitation frequencies ranging from 0.562 Hz down to 0.032 Hz. Four-point methodology was applied to extract the amplitude and phase of thermal wave's harmonic component. The phase images are analyzed to find qualitative and quantitative information about the defects.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.307-311
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• 1997

This paper describes influence of thermal deformation on nosic characteristics in high speed spindle systems. Heat generation in front, rear spindle bearings and built in motor lead to diverse thermal deformation of headstock with time. This deformation changes assemble tolerance in bearing housing, especially to elliptic form. The elliptic assemble tolerance generate high nosie level with dominant amplitude in double rotational frequency.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.697-700
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• 2005

Aquifer Thermal Energy Storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop an ATES system which has certain hydrogeological characteristics, understanding of the thermo hydraulic processes of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermo hydraulic transfer for heat storage is simulated using FEFLOW according to two sets of pumping and waste water reinjection scenarios of heat pump operation in a two layered confined aquifer. In the first set of model, the movement of the thermal front and groundwater level are simulated by changing the locations of injection and pumping well in seasonal cycle. However, in the second set of model the simulation is performed in the state of fixing the locations of pumping and injection well. After 365 days simulation period, the temperature distribution is dominated by injected water temperature and the distance from injection well. The small temperature change is appears on the surface compared to other slices of depth because the first layer has very low porosity and the transfer of thermal energy are sensitive at the porosity of each layer. The groundwater levels and temperature changes in injection and pumping wells are monitored to validate the effectiveness of the used heat pump operation method and the thermal interference between wells is analyzed.

• 소성∙가공
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• 제27권3호
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• pp.171-176
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• 2018

In this study, the cooling characteristics of dies were investigated in the hot stamping process of front pillars for automobile. Two identical dies were manufactured out of tool steels with different thermal conductivities. The dies were designed with curved channels for uniform cooling of the blank. Computational fluid dynamics (CFD) simulations were also carried out, which can consider the heat transfer among the coolant, die, and blank. Measured and simulated thermal histories of dies were compared, and it was shown that high conductivity tool steel has an excellent cooling capacity compared to conventional tool steel.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1073-1082
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• 1998

When thermal diffusivity is measured by laser flash method, the thermal diffusivity call be calculated front the assumption of the uniformly heated whole surface of the specimen. It has been known that the approximate 5% error is made by the non-uniform energy distribution on the specimen surface of laser pulse heat source. In this study, to obtain the highly-uniformed laser beam, which has both the low non-uniform heating error from non-uniform laser beam and the energy loss, research was carried out on no transmitting loss by optical fiber and high repetitions. In addition, heating error and thermal diffusivity were measured as the measuring positions were varied and compared with the results using the uniform and the non-uniform laser beams. In addition, dole to using the uniformalized laser beam, the whole surface of the specimen was heated uniformly and as a result, it was the thought that this was very effective to reduce the variations of the errors of the thermal diffusivity as the measuring positions were varied. It can be obtained that when the thermal diffusivity of POCO-AXM-5Q1 of SRM in NBS was measured with both the uniform and the non-uniform laser beams, the dispersion error of the former was from 2 to 2.5%, which was more improved than that of the latter.

• 마이크로전자및패키징학회지
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• 제21권3호
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• pp.63-66
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• 2014

본 연구에서는 3차원 적층 집적회로 구조에서 Cu TSV를 활용한 열관리 가능성에 대해 살펴보았다. Cu TSV가 있는 실리콘 웨이퍼와 일반 실리콘 웨이퍼 후면부를 점열원을 이용하여 가열한 후 전면부의 온도 변화를 적외선 현미경을 이용하여 관찰하였다. 일반 실리콘 웨이퍼의 경우 두께가 얇아지면서 국부적인 고온영역이 관찰됨으로서 적층 구조에서 층간 열문제의 가능성을 확인할 수 있었다. TSV 웨이퍼의 경우 일반 실리콘 웨이퍼보다 넓은 영역의 고온 분포를 나타내었으며, 이는 Cu TSV를 통한 우선적인 열전달로 인한 것으로 적층 구조에서 Cu TSV를 이용한 효과적인 열관리의 가능성을 나타낸다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.696-700
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• 2004

In the Korean seas, Sea Surface Temperature (SST) and Thermal Fronts (TF) were analyzed temporally and spatially during 8 years from 1993 to 2000 using NOAA/AVHRR MCSST. As the result of harmonic analysis, distributions of the mean SST were $10~25^{\circ}C,$ and generally SST decreased as latitude increased. SST increased in the order as following; the South Sea $(20\~23^{\circ}C),$ the East Sea $(17\~19^{\circ}C)$, and the West $Sea(13\~16^{\circ}C).$ Annual amplitudes and phases were $4\~11^{\circ}C,\;210\~240^{\circ}$ and high values were shown as following; the West Sea $(A1,\;9\~11^{\circ}C),$ the Northern East Sea $(A5,\;8\~9^{\circ}C),$ the Southern East Sea $(A4,\;6\~8^{\circ}C),$ the South Sea $(A3,\;6\~7^{\circ}C),$ the East China Sea $(A2,\;4\~7^{\circ}C)$ and phases; $A3\;(238\~242^{\circ}),\;A4\;(235\~240^{\circ}),\;A5\;(225\~235^{\circ}),\;Al\;(220\~230^{\circ}),\;A2\;(210\~235^{\circ}),$ respectively, Both of them were related inversely except the area A2, therefore the rest areas were affected by seasonal variations. TF were detected by Soble Edge Detection Method using gradient of SST. Consequently, TF were divided into 4 fronts; the Subpolar Front (SPF) based on the Cold Water Mass (low SST and salinity Subartic Water), resulting from the North Korea Cold Current (NKCC) and the East Sea Proper Cold Water in the middle and low layer, and the Warm Water Mass (high SST and salinity Subtropical Water), resulting from the Tsushima Warm Current (TWC) in area A4 and 5, the Kuroshio Front (KF) based on the Kuroshio Current (KC) and shelf waters in the East China Sea (ESC) in A2, and the South Sea Coastal Front (SSCF) based on the South Sea Coastal Water (SSCW) and TWC in A3. Also, the Tidal Front was weakly appeared in AI. TF located in steep slope of submarine topography. Annual amplitudes and phases were bounded in the same place, and these results should be considered to influence of seasonal variations.

• 대한기계학회논문집B
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• 제21권1호
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• pp.113-124
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• 1997

This work is performed to investigate the pressure drop and heat transfer characteristics in the air side of finned-tube heat exchanger for air conditioner. Experimental apparatus and method are described to simulate the heat exchanger performance by using the three times enlarged model. The pressure drop and heat transfer coefficient were measured and compared for the heat exchangers with a plane fin and a commercial strip fin. The measured data for the strip fin agree well with those of prototype within a few percentages. For the plane fin, the measured data had similar trend to Gray & Webb's correlation at high air velocity, however a new correlation is needed to give more accurate prediction at low air velocity. It is found that most heat was transferred around the front row of the two-row heat exchanger, and the ratio of thermal load at the front tube row was increased for decreasing air velocity.