Numerical investigation of dew condensation by using a phase change model considering the effect of non-condensable gases

Guangri Jin,Kwan-Soo Lee(이관수) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

동결융해시험에 의한 “CSG” 재료의 장기강도 및 내구 특성

김광일(Guangri Jin),김기영(Kiyoung Kim),문홍득(Hongduk Moon),권혁춘(Hechun Quan) 한국지반환경공학회 2016 한국지반환경공학회논문집 Vol.17 No.12

시공기술의 발전과 더불어 댐 · 제방 건설과 환경문제가 크게 대두되고 있는 실정이다. 최근 여러 국가에서 댐 · 제방 건설시 골재, 시공성, 기초지반에 대한 요구가 상대적으로 높지 않은 CSG(Cemented Sand and Gravel)재료를 활발히 연구, 적용하고 있다. CSG 재료는 시공현장 하상골재, 현장에서 발생하는 암버럭 등을 인위적으로 입도조정하지 않고 최대골재 치수만을 선별하여 소량의 시멘트와 혼합하여 강도증가 및 급속시공이 가능하다. CSG 재료는 인위적인 석산개발 등에 의한 환경파괴를 최소화함으로써 환경부하저감 및 공사비 등의 측면에서 비교적 경제적이며 친환경적이다. CSG 재료의 외부환경은 일반콘크리트가 접하는 수화열환경과는 달리 건습반복, 동결융해 등의 환경에 노출되게 된다. 그러므로 댐 · 제방구조물의 중요성을 감안하여 CSG 재료의 내구성에 대한 연구가 필요하다. 본 연구는 CSG 재료의 내구성에 대하여 고찰하고자 현장채취 CSG 코어재료에 대하여 동결융해 시험을 실시하였다. 시험결과, CSG 재료의 내구성 지수는 시멘트함량 0.4∼0.6kN/㎥의 경우 30∼40, 0.8∼1.0kN/㎥의 경우 40 이상으로 나타났다. 일축압축강도는 0.4∼0.6kN/㎥에서 동결융해 전의 30∼50%, 0.8∼1.0kN/㎥에서 동결융해 전의 40∼70%로 감소하는 것으로 나타났다. 결과적으로 시멘트함량 0.8kN/㎥ 이상의 경우 강도 및 내구성 측면에서 비교적 타당한 것으로 판단된다. With the development of construction technology, constructions of dam and levee (dike) as well as the environmental problems are becoming issues. Recently, many countries have tried to develop and used CSG (Cemented Sand and Gravel), which needs fewer requirements than others in aggregates, constructability and ground condition during the dam construction. Mixing up with small amount of cement, CSG is able to increase the strength and proceed accelerated construction without artificial gradation adjustment of riverbed aggregate and crushed rock on construction site. Thus, CSG can minimize environmental damage resulted from quarries mining and reduce cost of construction. Unlike heat of hydration condition that regular concrete usually met, CSG exposes to repeated dry-wet and freezing and thawing environment. Thus, consider the importance of structure of dam or levee, intensive study on the durability of CSG is needed. In this study, freezing and thawing experiment was carried out to evaluate the durability of CSG. In results, the durability factor of CSG is 30∼40 or >40 when the amount of cement is 0.4∼0.6kN/㎥ or 0.8∼1.0kN/㎥, respectively. The unconfined compressive strength is reduced to 30∼50% or 40∼70% when the amount of cement is 0.4∼0.6kN/㎥ or 0.8∼1.0 kN/㎥, respectively. Taken together, the strength and durability of CSG is reliable when the amount of cement is over 0.8kN/㎥.

Prevention of dew condensation on the case surfaces of ceiling-cassette indoor air conditioning units

Jin, Guangri,Lee, Kwan-Soo Elsevier 2018 Applied Thermal Engineering Vol.133 No.-

<P><B>Abstract</B></P> <P>We proposed a new method for preventing dew condensation on the case surfaces of ceiling-cassette indoor air conditioning units. We investigated the dew condensation problem numerically using a diffusion boundary layer phase-change model that incorporates the effect of non-condensable gases. By installing a blocking device on the case surface, we significantly reduced the suction flow of warm, humid air and the total condensation rate on the surface. We optimized the installation location, height, and angle of the blockage in order to minimize dew condensation. When the optimized blockage device was installed, and the air conditioning unit was operated at low discharge speed, we observed that the total numerical and experimental condensation rate fell by 41 and 30%, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new method for preventing dew condensation on the case surface of air conditioning indoor unit was proposed. </LI> <LI> The effect of non-condensable gases was incorporated in the phase change model. </LI> <LI> The installation of the optimized blockage led to a 41% reduction in the condensation rate. </LI> </UL> </P>

구속압에 따른 토사의 침투파괴 실험적 연구

김광일(Jin Guangri),임정열(Lim Jeong Yeul) 한국방재학회 2018 한국방재학회논문집 Vol.18 No.3

To study the properties of the base of sandy soil and internal erosion of dam body, we designed equipment for the experiment of seepage failure that was able to measure the confining pressure, changes of water head and amount of quicksand. In results, the amount of quick sand, differential head and flow velocity reduced with increase of confining pressure in the seepage failure experiment. In addition, the incident of erosion, differential head and critical velocity reduced with the increase of maximum particle diameter of sandy soil. In conclusion, the study showed the correlation of flow velocity of seepage failure with differential head and maximum particle diameter. 본 연구는 토사 지반 및 제체의 내부침식 특성을 분석하고자 구속압, 수두변화, 유사량을 측정 할 수 있는 침투파괴 실험 장비를 특수 제작하여 침투파괴 실험에 적용하였다. 분석결과 구속압이 증가할수록 파괴 시 발생하는 유사량이 적은 것으로 나타났으며, 파괴시의 수두차 및 유속은 구속압이 증가할수록 감소하는 것으로 나타나고 있다. 또한 토사의 최대입경이 증가할수록 침식 발생 및 파괴 수두차는 증가하고, 침식 발생 및 파괴 한계유속은 증가하는 것으로 나타나고 있다. 실험 결과를 통하여 수두차 및 최대입경에 따른 침투파괴 유속의 상관식을 제시하였다.

Soil-Bentonite 혼합토의 강도 및 투수 특성

김광일(Jin Guangri),임은상(Im Eunsang),김기영(Kim Kiyoung),신동훈(Sin Donghoon) 한국지반환경공학회 2010 한국지반환경공학회논문집 Vol.11 No.4

차수재로서 벤토나이트를 혼화재로 사용한 혼합토가 매립장, 제방, 댐 등의 다양한 구조물의 차수재로서 많이 이용되고 있다. 그러나 시공 시 외부하중, 성토하중 등에 의한 차수층의 전단파괴가 발생하여 침투수의 침투 등이 예상 되지만 일반적으로 혼합토의 투수계수만 고려할 뿐 혼화재양에 따른 강도변화는 고려하지 않고 있는 실정이다. 이에 본 연구에서는 벤토나이트 함량의 변화가 혼합토의 투수 및 강도에 미치는 영향에 대하여 고찰하고자 B댐 축조현장 부근 하상시료에 벤토나이트를 0~4%로 변화하면서 일련의 투수시험 및 강도시험을 실시하였다. 시험결과 투수계수는 벤토나이트 함량 4%에서 2.085E-07㎝/sec의 값을 가지는 것으로 나타났다. 일축압축강도 및 인장강도는 벤토나이트 함량이 증가함에 따라 증가하는 것으로 나타났으나, 삼축압축(CD)시험에 의한 벤토나이트 혼합토의 전단강도는 벤토나이트 함량 변화의 영향을 거의 받지 않는 것으로 나타났다. Soil mixture using bentonite as a cutoff material is used a lot for various structures such as landfills, banks and dams as cutoff materials. But seepage water is expected to seep since shear failure of filter layer occurs due to external load, embankment load when constructed. Generally, only coefficient of permeability of Soil Mixture is considered irrespective of the changes of intensity on amount of additives. This research is to study on how the changes of amount of bentonite affects permeability and strength of soil mixture. So successive experiments for measuring permeability and strength were conducted as the amount of bentonite changes from 0 to 4%, mixing with the bed material and then making specimens. Around construction site of B dam. As a result, 2.085E-07 ㎝/sec was shown when the amount of Soil Mixture was 4%. It is proved that unconfined compressive strength and tensile strength increase as the amount of bentonite increases, but saturation shear strength of bentonite soil mixture from the CD experiment is hardly influenced by the amount of bentonite.

A Dual Ionic pH-senstive copolymer for protein delivery

서영규,Li Guangri,강성우,이두성 한국고분자학회 2012 한국고분자학회 학술대회 연구논문 초록집 Vol.2012 No.10

Landslide Susceptibility Analysis in Baekdu Mountain Area Using ANN and AHP Method

Hechun Quan,Hongduk Moon,Guangri Jin,Sungsik Park 한국지반환경공학회 2014 한국지반환경공학회논문집 Vol.15 No.12

To analyze the landslide susceptibility in Baekdu mountain area in china, we get two susceptibility maps using AcrView software through weighted overlay GIS (Geographic Information System) method in this paper. To assess the landslide susceptibility, five factors which affect the landslide occurrence were selected as: slope, aspect, soil type, geological type, and land use. The weight value and rating value of each factor were calculated by the two different methods of AHP (Analytic Hierarchy Process) and ANN (Artificial Neural Network). Then, the weight and rating value was used to obtain the susceptibility maps. Finally, the susceptibility map shows that the very dangerous areas (0.9 or higher) were mainly distributed in the mountainous areas around JiAnShi, LinJiangShi, and HeLongShi near the china-north Korea border and in the mountainous area between the WangQingXian and AnTuXian. From the contrast two susceptibility map, we also Knew that The accuracy of landslide susceptibility map drew by ANN method was better than AHP method.

PCB channel을 이용한 LED light bulb용 히트싱크 설계

장대석(Daeseok Jang),김광일(Guangri Jin),김정한(Jung-Han Kim),이관수(Kwan-Soo Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

Light-emitting diodes (LED) are rapidly replacing conventional light bulbs in light applications because of their increased life span and energy efficiency. LED light bulb is used in various places, and the installation angle can vary based on the application and the environment, which significantly affects the cooling of the LED. If the heat dissipation performance of the LED light bulb is insuffi-cient, both the life of the LED and its luminous efficiency decrease. In this study, we analyzed the flow characteristics and thermal performance of cooling apparatus which has the vent in bulb case and is using the PCB as a heat sink. Furthermore, the thermal performance change of PCB heat sink according to the installation angle was analyzed.

Defrosting behavior and performance on vertical plate for surfaces of varying wettability

Kim, Hisuk,Jin, Guangri,Jeon, Jaehyeon,Lee, Kwan-Soo,rip Kim, Dong Elsevier 2018 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.120 No.-

<P><B>Abstract</B></P> <P>The defrosting behaviors and performances of super-hydrophilic, bare, and super-hydrophobic surfaces were experimentally investigated along different frost layer densities on a vertical plate. The defrosting behavior can be divided into three types based on the size of the water permeation layer. The defrosting behaviors of bare and super-hydrophilic surfaces were similar, whereas the super-hydrophobic surface behaved differently by allowing the frost layer to be easily removed from its surface. Defrosting performance was evaluated based on defrosting time and water retention ratio. Within the low frost layer density range, defrosting time did not depend on surface characteristics. However, as the density of the frost layer increased, defrosting time increased in the bare and super-hydrophilic surfaces, whereas in the super-hydrophobic surface, that time tended to decrease rather than increase. Water retention ratio was highest on the super-hydrophilic surface and lowest on the super-hydrophobic surface in all frost layer densities. Therefore, the defrosting performance of a super-hydrophobic surface was outstanding over a wide range of frost layer densities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The defrosting behaviors and performance were investigated with varying the surface wettability. </LI> <LI> The defrosting behaviors appeared in three types depending on frost layer density on all surfaces. </LI> <LI> The super-hydrophobic surface can easily remove the frost layer from the surfaces and has the best defrosting performance. </LI> </UL> </P>

Application of Artificial Neural Networks for Prediction of the Strength Properties of CSG Materials

Lim, Jeongyeul,Kim, Kiyoung,Moon, Hongduk,Jin, Guangri Korean Geo-Environmental Society 2018 한국지반환경공학회논문집 Vol.19 No.5

The number of researches on the mechanical properties of cemented sand and gravel (CSG) materials and the application of the CSG Dam has been increased. In order to explain the technical scheme of strength prediction model about the artificial neural network, we obtained the sample data by orthogonal test using the PVA (Polyvinyl alcohol) fiber, different amount of cementing materials and age, and established the efficient evaluation and prediction system. Combined with the analysis about the importance of influence factors, the prediction accuracy was above 95%. This provides the scientific theory for the further application of CSG, and will also be the foundation to apply the artificial neural network theory further in water conservancy project for the future.