• 한국표면공학회지
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• 제30권2호
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• pp.93-103
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• 1997

High temperature materials used in the elevated temperature and corrosive atmosphere must have the good oxidation resistance and preserve their own mechanical properties simultaneously. For the oxidation resistance, it is very important to form a protective oxide scale such as $Al_2O_3$ or $Cr_2O_3$ on the substrate. However, the additions of protective oxide forming elements such as Cr and Al in the alloy to enhance its oxidation resistance are limited due to the deleterious effects on their mechanical properties. PECVD(P1asma Enhanced Chemical Vapor Deposition) coating processes were employed to improve the oxidation resistance at high temperature. Cr and/or A1 were coated on the substrates of Ni and Inconel 600 at various temperatures of 400, 500, $600^{\circ}C$ and at different conditions of specimen surfaces. Then, coated specimens were exposed to isothermal and cyclic oxidation conditions in air at 1000 and $1100^{\circ}C$. In order to enhance the adhesion between the substrate and coated layer, heat treatments of the coated specimens were conducted in a vacuum. At isothermal oxidation experiments, Al-coated Ni specimen showed better oxidation resistance than pure Ni. At cyclic oxidation experiments at $1000^{\circ}C$. Cr and Al-coated specimen showed better oxidation resistance. Cr-coated Inconel 600 had also showed better oxidation resistance due to Cr in the substrate. By PECVD coating process, oxidation resistance could be improved, but it was not improved as expected due to the weakness of the adhesion between the substrate and the coated layer.

• 한국가시화정보학회지
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• 제21권2호
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• pp.34-45
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• 2023

When lithium-ion batteries operate out of the proper temperature range, their performance can be significantly degraded and safety issues such as thermal runaway can occur. Therefore, battery thermal management systems are widely researched to maintain the temperature of Li-ion battery cells within the proper temperature range during the charging and discharging process. This study investigates the cooling performance and isothermal maintenance of cooling materials by measuring the surface temperature of a battery cell with or without cooling materials, such as silicone oil, thermal adhesive, and phase change materials during discharge process of battery by the experimental and numerical analysis. As a result of the experiment, the battery pack filled with phase change material showed a temperature reduction of 47.4 ℃ compared to the case of natural convection. It proves the advanced utility of the cooling unit using phase change material that is suitable for use in battery thermal management systems.

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.420-424
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• 2019

포항산업과학연구원(RIST, Research Institute of Industrial Science & Technology)-고등기술연구원(IAE, Institute for Advanced Engineering)에서 제안한 합성천연가스(Synthetic Natural Gas, SNG) 제조공정(3개의 단열반응기와 1개의 등온반응기로 구성됨)에서, 합성가스와 함께 스팀을 공급함으로써 메탄화반응과 수성가스전환반응을 동시에 반응시켜 촉매층의 온도와 촉매 비활성화를 제어하였다. SNG 공정개발을 위해 본 연구에서는, 포항산업과학연구원에서 제조한 니켈계 촉매를 사용하여 낮은 $H_2/CO$ 비($CO_2$ 22% 포함) 조건에서의 메탄화반응 특성을 평가하였다. 운전조건(1차 단열반응기의 $H_2O/CO$ 비, 4차 등온반응기의 운전온도 범위 등)은 이전의 연구 결과를 반영하였으며, 동일한 조건을 유지하면서 파일럿 규모의 SNG 공정을 운전하였다. 그 결과, 파일럿 규모의 SNG 공정은 안정적으로 운전되었으며, CO 전환율 100%, $CH_4$ 선택도는 96.9% 그리고 $CH_4$ 생산성은 $660ml/g_{cat}{\cdot}h$의 값을 얻었다.

• Korea-Australia Rheology Journal
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• 제12권3_4호
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• pp.165-173
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• 2000

Three-dimensional numerical simulation of isothermal/nonisothermal coextrusion process of two immiscible polymers through a rectangular channel has been done using the finite element method. The encapsulation phenomenon with the less viscous layer encapsulating the more viscous layer was investigated with the generalized Newtonian fluids. The interface position around the symmetric plane obtained by numerical simulation nearly coincided with the one observed in experiments, but the degree of encapsulation was less than the one observed experimentally. Open boundary condition method was found to be applied to the simulation of nonisothermal coextrusion process, however, the results are not far from those using the fully developed boundary condition, because the temperature development along the downstream direction is very slow in the case of convection dominated flow. When the inlet velocity is increased, the interface profile does not change in isothermal flow, while it moves upward in nonisothermal situation. The degree of encapsulation decreases along the downstream direction in nonisothermal flow. When the inlet temperature increases compared to the wall temperature, the outlet interface moves downward and the degree of encapsulation increases. The difference of degree of encapsulation between the simulation and the experiments seems to arise from the viscoelastic effect of the materials. It was concluded that the nonisothermal effect alone does not explain the complex coextrusion process and the viscoelastic effect needs to be considered.

• 접착 및 계면
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• 제11권1호
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• pp.15-25
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• 2010

본 연구에서는 레이온직물에 대하여 $180^{\circ}C$ 및 $200^{\circ}C$의 비교적 낮은 온도영역에서 장시간 동안 등온 안정화공정을 수행하였다. 등온 안정화공정 전과 후의 변화된 레이온직물의 중량감소율, 치수변화율, X-선 회절, 그리고 전자현미경을 사용하여 섬유 형태를 관찰한 결과, 레이온 프리커서 섬유의 화학적, 물리적 변화는 $200^{\circ}C$ 이하의 안정화온도에서도 지속적이면서 서서히 진행되는 것으로 확인되었다. 그리고 안정화공정 전에 사용한 네 종류의 화학전처리제는 레이온직물의 특성변화에 서로 다른 영향을 주는 것으로 조사되었다. 결과적으로, 주어진 안정화 조건하에서 $H_3PO_4$와 $Na_3PO_4$$는 레이온직물의 안정화 반응을 촉진시키는 역할을 하는 반면, $NH_4Cl$과 $ZnCl_2$는 안정화 반응을 더디게 하거나 지연시키는 역할을 하는 것으로 판단되었다. 또한 $350^{\circ}C$에서 행한 2차 안정화에서는 $H_3PO_4$가 상대적으로 가장 낮은 직물의 중량감소율을 보여주었으며, 난연 기능을 가지고 있는 인산이 2차 안정화 단계에서도 후속 반응을 다소 더디게 하는데 기여한 것으로 사료되었다.

• Composites Research
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• 제33권2호
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• pp.44-49
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• 2020

본 연구에서는 시차주사 열량계(differential scanning calorimetry, DSC)를 이용하여 진공백 성형 공정에 사용되는 탄소 섬유 프리프레그의 경화 거동을 연구하였다. 프리프레그를 이용한 동적주사 시험을 통해 전체 발열량(ΔH_total = 537.1 J/g)을 측정하였고, 130℃~180℃에서 등온주사 시험을 실시하였다. 등온주사 시험의 결과는 온도가 올라감에 따라 발열 반응이 증가되는 것을 확인하였다. 시험 결과를 토대로 수지의 경화 거동을 분석하기 위하여 Kratz 모델을 적용하였다. 서로 다른 경화 사이클로 제작된 평판의 경화도를 경화 예측 모델과 실험값을 비교하였다. 경화 예측 모델은 실험값 대비 3.4% 이하의 오차율을 보여 결과가 잘 부합하는 것을 확인하였다.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.295-303
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• 2006

The pulp yield was improved by about 4.5-5% when polysulfide (PS) and anthraquinone (AQ) were added to the kraft cooking liquor (white liquor). The exchange of the black liquor with fresh white liquor further increased the yield. The highest pulp yield was obtained when the PS cooking liquor containing 70% of total active alkali (AA) and 100% of AQ was used from the beginning of the reaction and the black liquor was exchanged with fresh white liquor containing the residual 30% of AA just after temperature reached $135^{\circ}C$. There was a good correlation between kraft pulp yields of a hardwood species and the ratios of the amount of xylose to glucose (X/G ratio), liberated by an acid hydrolysis of the pulps. However, the correlation was dependent on raw material wood species. Therefore, it is required in advance to establish a correlation between the yields and X/G ratios for raw material wood species of a target pulp in order to estimate pulp yield using X/G ratio. The X/G ratios of relatively high yield pulps showed higher values than those expected from the correlation. In a mill trial, the superiority of the PS-AQ isothermal cooking (ITC) process over the kraft ITC process was confirmed by examining X/G ratio of pulps obtained. The pulp yield in the PS-AQ ITC process was estimated at about 57.0%. This yield is very high, which indicates that reaction conditions of the PS-AQ ITC process are optimal.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.174-181
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• 1999

In this paper the technique to predict tool wear theoretically in shearing process is suggested. The tool wear in the process affects the tolerances of final pans, metal flows and costs of processes. In order to predict the tool wear the deformation of workpiece during the process is analyzed by using non-isothermal finite element program. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. Results obtained from finite element simulation, such as nodal velocities and nodal forces, are transformed into sliding velocity and normal pressure on tool monitoring points respectively. The monitoring points are automatically generated and the wear rates on these points are accumulated during the process. It is assumed that the wear depth on the tool surface is linear function of the lot sizes based upon the known experimental results. The influence of clearance between die and punch upon tool wear is also discussed.

• 폴리머
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• 제25권3호
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• pp.359-366
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• 2001

본 연구에서는 유리섬유/에폭시수지 복합재료의 등온물리시효 거동을 torsional braid analysis (TBA)-torsion pendulum을 이용하여 따양한 경화도(유리전이온도로 모니터된)와 등온시효온도(T$_{a}$ )에 대하여 조사하였다. 이때 시효온도는 1$0^{\circ}C$에서 $130^{\circ}C$로, 경화도는 $T_g$=$76^{\circ}C$에서 완전 경화물의$ T_g$=$177^{\circ}C$로 변화시켰다. 모든 경화도에서 등온물리시효 효과가 $T_g$ 부근의 일정온도 영역에서 탄성율과 대수감소율의 변화로 나타났다. 일정 시효온도에서 시효시간에 따른 탄성율의 변화로부터 결정된 등온물리시효속도는 $T_a$=$90^{\circ}C$ 아래에서 경화도가 증가함에 따라 감소하다가 증가하는 양상을 보였다. 시효속도와 ($T_g$-$T_a$)의 그림에서 평행과 수직 이동에 의해 중첩이 됨을 확인할 수 있었으며, 이는 물리시효과정이 경화반응에 의한 화학구조의 변화에 영향을 받지 않는다는 것을 의미한다. 본 연구에서는 약 $70^{\circ}C$ 아래의 시효온도에서는 등온시효동안 수분이 흡수되며 그것으로 인해 시효속도가 감소한다는 전을 알 수 있었다. 이는 물분자와 사슬의 히드록 시기와의 강력한 극성결합으로 사슬의 운동성감소에 기인하는 것으로 생각된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.432-435
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• 1996

The performance of one-column isothermal PSA process is assessed by dynamic simulator, gPROMS. The four-step and five-step processes are compared. A five-step process is employed in order to show the effect of the addtional cocurrent depressurization step on the four-step PSA process. Two processes parameters, purity and recovery of SO$_{2}$ are used for the performance comparison. The results of dynamic simulation show that four-step process is superior to five-step process in recovery, but not in purity.