• 한국산학기술학회논문지
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• 제20권1호
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• pp.170-178
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• 2019

최근 에너지 절감에 대한 관심도가 높아짐에 따라 에너지 소비가 높은 형광등과 백열등을 대체하는 친환경소재인 LED의 조명을 활용하는 움직임이 활발하다. 그러나, 고출력 LED의 경우 발열에 의한 열화현상 때문에 수명이 단축되는 현상이 발생하게 된다. 이에 대한, 해결방안으로 본 논문은 LED Packing중 방열판표면의 거칠기 처리를 통하여 열전달 계수를 증대시킴으로서 LED 수명연장 효과를 평가하였다. 거칠기 공정은 사포 및 샌드블라스트를 이용하여 진행하였다. 각 표면처리 공정에 따른 거칠기 및 표면적 변화를 정량적으로 평가하였으며, 열전달 계수를 측정하였다. 샌드블라스트, 사포를 이용하여 알루미늄 표면에 거칠기처리를 진행했을 경우 미 처리 시 보다 높은 대류 열전달 계수를 얻을 수 있었고, 샌드블라스트 처리 시 약 82.76%의 높은 방열 효율 향상을 얻을 수 있어, 이를 방열판에 적용할 시 큰 경제적 부담 없이 기존대비 더 높은 방열효율 증대를 통해 LED 수명을 대폭 연장 시킬 것으로 기대된다.

• 공업화학
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• 제31권5호
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• pp.575-580
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• 2020

본 연구에서는 열 안정성 염 제거장치가 추가된 아민 재생 공정을 모사하고, 폐수 량, 열 안정성 염 제거 량, MDEA(methyl diethanolamine) 손실량을 고려한 최적 운전조건 도출 전략을 제시하였다. 산성 가스를 흡수 및 탈거하는 아민 재생공정에서 열 안정성 염은 공정 장비 및 아민 용액의 흡수 효율을 저해한다. 열 안정성 염 제거 방법 중 하나인 이온교환수지법은 NaOH와 같은 강 염기성 용액을 사용하여 중화반응을 통해 염을 제거시키는 방법이다. 공정 모델링 과정에서 산성 가스의 탈거 과정은 Radfrac 모델을 사용했고, 반응의 평형상수는 Gibbs 자유에너지를 사용하여 계산하였다. 탈거된 아민 용액의 일부는 열 안정성 염 제거 장치로 들어가게 되고, 제거 장치는 중화반응을 이용한 Rstoic 모델을 사용하였다. 실제 운전데이터와 시뮬레이션 결과를 비교하여 검증하였고, 제거 장치로 들어가는 질량 유량을 조절하여 사례연구를 하고 최적 운전 조건을 제시하였다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2002년도 춘계 학술발표회 논문집
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• pp.21-27
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• 2002

Catalytic combustor with heat exchangers are often employed in process technology where a compact design is required [1]. The use of fin and tube heat exchanger offers the enhanced surface area for heat exchange. The recent progress and performance of the fin-tube heat exchanger, especially airside, has been reviewed extensively by Wang[2].(Omitted)

• 한국기계연구소 소보
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• 통권19호
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• pp.23-30
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• 1989

Heat transfer phenomena of solidification process of the phase change material within cylindrical can is studied experimentally. N-Eicosane paraffin wax is used for phase change material and its melting temperature is 309.8 K. In order to achieve higher heat transfer rate of latent heat storage apparatus, fins in made of copper are used in the cylindrical can. If there are fins in cylindrical can, we can know that the inward latent heat energy in paraffin can be effectively transfered to cooling water than if finless.

• Journal of Ginseng Research
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• 제28권3호
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• pp.143-148
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• 2004

Brown color intensity has been a major factor to estimate the quality of red ginseng and its products. This study deals with the relationship between the browning reaction of ginseng root and two compounds, arginyl-fructosyl-glucose(Arg-fru-glc) and arginyl-fructose (Arg-fru), in the model system of steaming and heat-drying processes for the preparation of red ginseng. During the steaming process, a marked decrease of starch and a considerable formation of maltose occurred in main roots of raw ginseng, but the formation of glucose was scarcely observed. After the heat-drying process, the brown color intensity of the powdered preparation of steamed main roots was 3 to 4 times higher than that of the powdered preparation of raw main roots. Also, when the heat- drying process was done with the addition of L-arginine, brown color intensity of the powdered preparation of steamed main roots was 12 to 13 times higher than that of the powdered preparation of raw main roots. The amount ratios of browning reaction products formed from sugar compounds and amino acids in the model system of steaming and heat-drying treatments in vitro were in order of xylose > glucose > fructose > maltose > dextrin (DE 9) > sucrose > dextrin (DE 8) and soluble starch. Each solution of Arg-fru-glc and Arg-fru that were synthesized chemically from maltose plus L-arginine and glucose plus L-arginine, respectively, changed from colorless to brown color during the heat-drying treatment. Amino acids or sugars were effective on the acceleration of each browning reaction of Arg-fru-gIc and Arg-fru during the heat-drying treatment.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3017-3029
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• 2023

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m². The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

• 열처리공학회지
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• 제36권3호
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• pp.121-127
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• 2023

When high carbon steel is heated in an appropriate austenizing temperature range and subjected to austempering, the size and shape of lamellar structure can be controlled. The high carbon steel sheet having the pearlite structure has excellent elastic characteristics because it has strong restoring force when properly rolled, and is applied in a process known as patenting-process using lead bath. In the case of isothermal treatment using lead-medium, it is possible to quickly reach a uniform temperature due to high heat transfer characteristics, but it is difficult to replace it with process technology that requires treatment to remove harmfulness lead. In this study, we intend to develop fluidization technology using garnet powder to replace the lead medium. After heating the high-carbon steel, the cooling rate was changed by compressed air to the vicinity of the nose of the continuous cooling curve, and then maintained for 90 s and then exposed to room temperature. The microstructure of the treated specimens were analyzed and compared with the existing products treated with lead bath. The higher the flow rate of compressed air, the faster the cooling rate to the pearlite transformation temperature, so lamellar spacing decreases and the hardness tends to increase.

• 반도체디스플레이기술학회지
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• 제22권3호
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• pp.119-124
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• 2023

In this study, experimental approach of the measurement of condensation and evaporation heat transfer coefficients is discussed for mixed refrigerants using in the ultra low-temperature cooling system for semiconductor etching process. An experimental apparatus was described performing the condensation and evaporation heat transfer measurements for mixed refrigerants. The mixed refrigerant used in this study was composed of the optimal mixture determined in previous research, with a composition of Ar:R14:R23:R218 = 0.15:0.4:0.15:0.3. The experiments were conducted over a temperature range from -82℃ to 15℃ and at pressures ranging from 18.5 bar to 5 bar. The convection heat transfer coefficients of the mixed refrigerant were measured at flow rates corresponding to actual operating conditions. The condensation heat transfer coefficient ranged from approximately 0.7 to 0.9 kW/m2K, while the evaporation heat transfer coefficient ranged from 1.0 to 1.7 kW/m2K. The detailed discussion of the experimental methods, procedures, and results were described in this paper.

• 소성∙가공
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• 제7권6호
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• pp.530-538
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• 1998

Elimination of the heat treatment process is very important in automation of metal forming since controlling heat treatment by computer has many difficulties and it has bottle neck problem. non-heat-treated steels materials which are not in need of heat treatment have been developed for cold forging. However to apply non-heat-treated steel to structural parts. it is necessary to prove reliability of mechanical properties. In order to define the reliability of mechanical properties we have investigated microstructure, hardness, the tensile strength compressive strength and tensile fatigue strength for both steels. Considering the results of high cycle fatigue test for both specimen the characteristics of non-heat-treated steel are decided on the yield strength, It has same tendency for heat-treated steel. Therefore non-heat-treated steel which has the appropriate yield strength may be applied in cold forging.

• Journal of Welding and Joining
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• 제19권5호
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• pp.492-498
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• 2001

In the previous study, temperature monitoring of case about shrinkage fit process was performed and heat transfer model was developed in detail by feedback and tuning among monitoring result, process investigation, and analysis result. The gap element in contact between case and core was effectively used in analysis model. In present study, following things are performed to solve deformation of case due to shrinkage fit process on the basis of previous result. Above all, mechanical material properties of case are measured by case specimen for deformation analysis considering weldment of case. Deformation of case before and after shrinkage fit process is measured, too. Three dimensional deformation model is developed by the comparison and inspection between these experimental data and analysis results. Deformation analysis is simulated with the result of heat transfer analysis, in other words, non-coupled analysis is used. Finally the countermeasure for deformation is brought up through those.