• International Journal of Fluid Machinery and Systems
• /
• 제8권2호
• /
• pp.113-123
• /
• 2015

The efficiency of the ventilation system is a key point for durable and reliable electric generators. The design of such system requires a detailed understanding of the air flow in the generator. Computational fluid dynamics (CFD) has the potential to resolve the lack of information in this field. The present work analyses the air flow inside a generator model. The model is designed using a CFD-based approach, and manufactured by taking into consideration the experimental and numerical requirements and limitations. The emphasis is on the possibility to accurately predict and experimentally measure the flow distribution inside the stator channels. A major part of the work is focused on the design of an intake and a fan that gives an evenly distributed flow with a high flow rate. The intake also serves as an accurate flowmeter. Experimental results are presented, of the total volume flow rate, the total pressure and velocity distributions. Steady-state CFD simulations are performed using the FOAM-extend CFD toolbox. The simulations are based on the multiple rotating reference frames method. The results from the frozen rotor and mixing plane rotor-stator coupling approaches are compared. It is shown that the fan design provides a sufficient flow rate for the stator channels, which is not the case without the fan or with a previous fan design. The detailed experimental and numerical results show an excellent agreement, proving that the results reliable.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
• /
• pp.676-683
• /
• 2003

A laboratory experiment using artificial fracture rocks was used to understand the 3-dimensional dispersion of a tracer and the mixing process in a fractured network. In this experiment, 12cm polystyrene foam cubes with two electrodes for monitoring electric conductivity (EC) were used as artificial fractured rocks. Distilled water with 0.5mS/m was used as a tracer in water with 35mS/m and the difference of EC between the tracer and the water was monitored by a multipoint simultaneous measurement system of electrical resistance. The results showed that even if the fracture arrangement pattern was not straight in the direction of the flow, the tracer did not diffuse along individual fractures and an oval tracer plume, which was the distribution of tracer concentrations, tended to be form in the direction of the flow. The vertical cross section of the tracer distribution showed small diffusivity in the vertical direction. The calculated total tracer volume passing through each measurement point in the horizontal cross section showed while that the solute passed through measurement points near the direction of hydraulic gradient and in other directions, the passed tracer volumes were small. Using Peclet number as a criterion, it was found that the mass distribution at the fracture intersection was controlled in the stage of transition between the complete mixing model and the streamline routing model.

• Bulletin of the Korean Chemical Society
• /
• 제31권11호
• /
• pp.3221-3224
• /
• 2010

This study investigates the requirements of lithium-air cathodes, which directly influence discharge capacity. The cathodes of Li-air cell are made by using five different carbon materials, such as Ketjen black EC600JD, Super P, Ketjen black EC300JD, Denka black, and Ensaco 250G. The Ketjen black EC600JD provides discharge capacity of 2600 mAh/g per carbon weight, while that of Ensaco 250G shows only 579 mAh/g. To figure out the differences of discharge capacity from carbon materials, their surface area and pore volume are analyzed. These are found out to be the critical factors in determining discharge capacity. Furthermore, carbon loading on Ni foam and amounts of electrolyte are significant factors that affect discharge capacity. In order to investigate catalyst effect, electrolytic manganese dioxide (EMD) is incorporated and delivered 4307 mAh/g per carbon weight. This infers that EMD facilitates to break $O_2$ interactions and leads to enhance discharge capacity.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.18-21
• /
• 2004

A GFRP based composite blade was developed for a 750kW wind energy conversion system of type class I. The blade sectional geometry was designed to have a general shell-spar structure. The load cases specified in the IEC61400-1 international specification were considered. For withstanding all relevant extreme loads, the structural analysis for the complete blade was performed using a commercial FEM code. The static load carrying capacity, buckling stability, blade tip deflection and natural frequencies at various rotational speeds were evaluated to satisfy the strength requirements in accordance with the IEC61400-1 and GL Regulations. For designing a lightweight blade, the thickness and the lay-up pattern of the skin-foam sandwich structures were optimized iteratively using the DOT program T-bolts were used for joining the blade root and the hub, which were modeled using a 3D FE volume model. In order to confirm the safety of the root connection, the static stresses of the thick root laminate and the steel. bolts were predicted by taking account of the bolt pretension and the root bending moments. The calculated stresses were compared with the material strengths.

• Geomechanics and Engineering
• /
• 제35권6호
• /
• pp.637-646
• /
• 2023

At present, the research on wave propagation in graphene platelet reinforced composite plates focuses on the propagation behavior of bulk waves, in which the effect of boundary condition is ignored, there is no literature report on propagation behaviors of guided waves in graphene platelet reinforced metal foams (GPLRMF) plates. In fact, wave propagation is affected by boundary conditions, so it is necessary to study the propagation characteristics of guided waves. The aim of this paper is to solve this problem. The effective performance of the material was calculated using the mixing law. Equations of motion of GPLRMF plate is derived by using Hamilton's principle. Then, the eigenvalue method is used to obtain the expressions of bending wave, shear wave and longitudinal wave, and the degradation verification is carried out. Finally, the effects of graphene platelets (GPLs) volume fraction, elastic foundation, porosity coefficient, GPLs distribution types and porosity distribution types on the dispersion relations are studied. We find that these factors play an important role in the propagation characteristics and phase velocity of guided waves.

• 한국수산과학회지
• /
• 제15권4호
• /
• pp.283-290
• /
• 1982

Sardine and mackerel so called dark muscled fish have been underutilized due to the disadvantages in bloody meat color, high content of fat, and postmortem instability of protein. Recent efforts were made to overcome these defects and develope new types of product such as texturized protein concentrates and dark muscle eliminated minced fish. Approach of this study is based on the rapid dehydration of foamed fish-starch paste by dielectric heating. In process comminuted sardine meat was washed more than three times by soaking and decanting in chilled water and finally centrifuged. The meat was ground in a stone mortar added Ivith adequate amounts of salt, foaming agent, and other ingredients for aid to elasticity and foam stability. The ground meat paste was extruded in finger shape and heated in a microwave oven to give foamed, expanded, and porous solid structure by dehydration. Dielectric onstant $(\varepsilon')$ and dielect.ic loss $(\varepsilon")$ values of sardine meat paste were influenced by wavelength and moisture level. Those values at 100 KHz and 15 MHz were ranged 2.25-9.86; 2.22-4,18 for E' and 0.24-19.24; 0.16-1.20 for E", respectively, at the moisture levels of $4.2-13.8\%$. For a formula for fish-starch paste preparation, addition of $20-30\%$ starch (potato starch) to the weight of fish meat, $2-4\%$ salt, and $5-10\%$ soybean protein was adequate to yield 4-5 folds of expansion in volume when heated. Addition of e99 yolk was of benefit to micronize foam size and better crispness. In order to provide better foaming and dehydration, addition of $0.2-0.5\%$sodium bicarbonate, foaming agent, was proper to result in foam size of 0.5-0.7 mm and foam density of $200-400\;/cm^2$ which gave a good crispness. Heating time was depended upon the moisture level of fish-starch paste. For a finger shaped paste (1.0cm. $D\times10cm.L$) heating for 150-200 sec. in a microwave oven (700W. 2.45GHz) was sufficient to generate foams, expand, and solidify the porous structure of fish-starch paste. When the moisture content was above $55\%$ browning and scorching was deepened due to over-expansion and over-heating whereas the crispness was hardened by insufficient expansion at lower moisture content. In quality evaluation of the product, chemical composition of $30\%$ starch and $3\%$ salt added product was moisture $8.8\%$, lipid $2.4\%$, carbohydrate $46.7\%$, protein $36.1\%$, and ash $6.0\%$. Eleven membered panel test evaluated that fish-starch paste was acceptable in color, crisp-ness, taste, except a trace of fishy odour which could be masked by the addition of spice extracts.

• 콘크리트학회논문집
• /
• 제23권2호
• /
• pp.151-158
• /
• 2011

선발포 방식을 통해 제조되는 기포 콘크리트에서 기포는 밀도, 강도, 공극 등의 물리적 특성에 영향을 끼치는 주요인이다. 기포 콘크리트에 대한 연구가 꾸준하게 진행되었지만, 기포 자체의 특성에 관한 연구는 화학적인 분야를 제외하고는 거의 없는 실정이다. 그러므로 용도에 적합한 기포 콘크리트를 제조하기 위해서는 기포의 성상에 대한 연구가 필수적으로 선행되어야 한다. 기포 콘크리트의 제조에서 기포를 유효하게 이용하기 위해서는 기포의 특성을 평가해야만 한다. 이 연구에서는 기포의 특성을 알아보기 위해 기포제 종류 및 농도 변화에 따른 기포의 특성에 관한 검토를 수행하였다. 기포의 특성을 알아보기 위해 사용한 기포제는 계면활성제계, 수지비누계, 단백질계 기포제를 사용하였고 기포제의 농도는 기포제 종류에 따라 0.05~13% 범위로 설정하였다. 측정 항목은 발포율, 기포 용적, 수용액 용적, 기포 크기 및 분포를 측정하였다. 분석 결과, 기포제 종류와는 상관없이 기포제 농도가 높을수록 발포율은 증가하는 것으로 나타났고, 기포제 농도는 기포, 수용액 용적 변화, 기포 크기 분포에도 영향을 끼치는 것으로 나타났다. 기포의 안정성 측면에서 단백질계가 계면활성제, 수지비누계 보다 높은 안정성을 나타냈다. 기포의 형상에서는 계면활성제계, 수지 비누계는 다각형의 기포를, 단백질계는 구형의 기포를 형성하였다.

• 생물환경조절학회지
• /
• 제11권3호
• /
• pp.108-114
• /
• 2002

CGF(cellular glass foam)는 폐기된 유리물질을 재가공하여 입자화한 것으로 통기성과 배수성이 뛰어난 펄라이트와 이화학적 성질이 유사하여 칼란코에 영양번식용 배지로의 가능성이 있다. 따라서 CGF와 펄라이트를 각각 입상암면과 피트모스를 다양한 부피비로 혼합하여 Kalanchoe blossfeldiana ‘Gold Strike’의 생육을 비교하였다. 배지의 입자크기는 CGF 2.0~4.0mm, 펄라이트 1.2~4.0mm를 사용하였다. 평균온도 18.2$^{\circ}C$와 상대습도 66.7% 조건의 미스트상에서 전조처리(명기 14h.d$^{-1}$, 암기 10h.d$^{-1}$)하여 재배하였다. 초장, 근장, 경경. 엽수, 엽면적, 발근율, 지상부와 지하부의 생체중과 건물중, 총 엽록소 농도, 그리고 배지의 이화학성을 조사하였다. 모든 처리구에서 100%의 발근율을 보였다. CGF와 펄라이트가 혼합된 배지의 이화학적 특성은 처리간 유의차가 적었다. 또한 CGF의 혼합배지에서 칼란코에의 생육은 펄라이트의 혼합 배지와 비교해 유사하거나 오히려 우수한 생육을 보였다 따라서 칼란코에의 영양번식용 배지로서 CGF의 사용 가능성이 입증되었으나 추후 CGf를 이용하기 위해 보다 폭넓은 실증실험과 분석이 필요하며, 높은 pH를 보정할 수 있는 적정 양액 개발되어야 할 것이다.

• 한국건축시공학회지
• /
• 제16권1호
• /
• pp.9-15
• /
• 2016

건물에서 에너지 손실이 가장 큰 부위는 외피로서, 이 부분의 에너지 손실을 감소하기 위한 연구가 활발히 진행되고 있으나 이는 대부분 창호 및 단열재를 사용한 연구이며 건물 외피의 70% 이상을 차지하고 있는 콘크리트에 대한 연구는 미미한 실정이다. 따라서 건물의 에너지 손실을 최소화하기 위해서는 콘크리트 자체에서 단열성능을 확보할 수 있어야 하며 이에 대한 연구가 필요하다. 이에 본 연구에서는 보통콘크리트보다 열전도율을 2배 이상 개선시킨 구조용 단열성능향상 콘크리트 개발 연구의 일환으로 마이크로기포제, 규조토 미분말, 경량골재를 사용하였으며, 콘크리트 내부공극을 다량확보하여 열전도율을 낮추고자 하였다. 실험결과, 슬럼프와 공기량은 양호한 결과를 나타내었으며, 단위용적질량에서는 마이크로기포제를 사용한 모든 배합에서 보통콘크리트보다 14.3~35.1 % 감소된 결과를 나타내었고 압축강도는 단열성능 향상 재료를 사용하여 다소 감소하는 경향을 나타내었으나 본 실험의 목표 강도(24MPa)를 모두 만족하였다. 또한 열전도율은 보통콘크리트 대비 최대 2배 이상 개선된 결과를 나타내었다.

• 지질공학
• /
• 제30권2호
• /
• pp.185-198
• /
• 2020

고밀도 급속 팽창재는 주입과 동시에 화학반응으로 인한 순간 발포반응이 생겨 주입재료의 고결부피를 증가시키는 공법으로써 구조물 축조 시 지반의 안정성 확보, 침하 구조물복원 및 차수에 효과적인 공법이다. 이와 관련하여 본 연구에서는 주입재료의 역학적 실험을 통하여 구조물 기초지반의 안정성 평가와 현장시공을 이용한 지내력 증대 효과를 분석하였다. 실험 결과, 사질토 지반의 경우 주입재의 주입 후 약 10.5% 정도 흙의 단위 중량이 감소 된 것으로 확인되었으며, 구조물에 대한 허용지지력 모두 안전하다고 판단되었고 지반개량 후 각 단면별 침하량은 허용 침하량 5 cm 이내인 2.28, 1.55, 0.46 cm로써 안전하다고 판단되었다. 현장 실험 후 대상 건축물의 최상층에 5개의 경사계를 설치하여 X, Y축에 대한 변위를 측정하였다. 계측결과, 시공 후 약 16개월(509일)동안 구조물의 부등침하 또는 침하균열 현상과 관련된 변위는 측정되지 않았다. 이는 급속 팽창재의 주입 후 지반의 안정성이 충분히 증대된 것이라고 판단할 수 있다.