• Transactions of the KSME C: Technology and Education
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• v.3 no.1
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• pp.23-28
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• 2015

In this paper, we performed the design optimization dual-shell and tube heat exchanger on exhaust waste heat recovery for gas heat pump using CFD and RSM. CFD analysis is useful to design the complex structure such as double shell and tube heat exchanger. By computer simulation, engineers can assess the feasibility of the given design factors and change them to get a better design. But if one wishes to perform complex analysis on the simulation, such dual-shell and tube heat exchanger for GHP, the computational time can become overwhelming. CFD is powerful but it takes a lot of time for complex structure. Therefore, the CFD analysis is minimized by the optimization using the RSM method. As a result, the number of baffle and tube are optimized by 6 baffles and 25 tubes for heat transfer and flow friction. And then pressure drop and heat transfer is improved about 12.2%. We confirm the design optimization using CFD and RSM is useful on complex structure of heat exchanger.

• Korean journal of food and cookery science
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• v.19 no.5
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• pp.616-623
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• 2003

Waxy barley brans were collected during the pearling process. The extraction of $\beta$-glucan from barley bran was effected by the extraction conditions. The $\beta$-glucan content increased with temperature, but not with pH. The highest yield, 6.5%, was achieved at pH 7.0 and 55$^{\circ}C$. At pH 10 and 45$^{\circ}C$, 48.5% of the $\beta$-glucan in barley bran was recovered in the gum product, with 54.6% purity. The protein and starch contaminations were high, reaching 13.6 and 23.7%, respectively. The $\beta$-glucan content was greatest in the subaleurone and aleurone regions (bran fractions 1, 2, 3 and 4), and declined considerably toward the inner layers. A monosaccharide analysis of the purified, $\beta$-glucan, from bran fractions 1, 2, 3 and 4, indicated that glucose constituted the majority of the gum. The small amounts of the arabinose and xylose found in the gum may indicate the presence of arabinoxylans as minor constituents. The molecular weights of the $\beta$-glucans isolated from bran fractions 1,2 and 3 were found to be 4.09${\times}$10$^{5}$ ∼-4.41${\times}$10$^{5}$ . The major glycosidic linkages of the $\beta$-glucans demonstrated the presence of 2, 4, 6-Me-Glc and 2, 3, 6-Me-Glc. When flow behaviors of barley bran $\beta$-glucan were examined, $\beta$-glucan exhibited pseudoplastic fluid properties.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.132-148
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• 2019

Recently, safety and environmental concerns have become major social issues. Especially, a special underground-safety law has been made and enacted to prevent ground subsidence around construction sites. For environmental problems, several researches have started or will start on characterization of contaminated sites, in-situ environmental remediation in subsurface, and monitoring of remediation results. As a part of the researches, geophysical surveys, which have been mainly applied to explore mineral resources, geological features or ground, are used to characterize not only contaminated areas but also fluid flow paths in subsurface environments. As a basic study for the application of geophysical surveys to detect contamination in subsurface, this paper analyzes previous researches to understand changes in geophysical properties of contaminated zones by various contaminants such as leachate, heavy metals, and non-adequate phase liquid (NAPL). Furthermore, this paper briefly introduces how geophysical surveys like direct-current electrical resistivity, induced polarization and ground penetration radar surveys can be applied to detect each contamination, before analyzing case studies of the applications in contaminated areas by NAPL, leachate, heavy metal or nitrogen oxides.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.8-13
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• 2016

A top-seeded solution growth (TSSG) is a method of growing SiC single crystal from the Si melt dissolved the carbon. In this study, multiphysics modeling was conducted using COMSOL Multiphysics, a commercialized finite element analysis package, to get analytic results about electromagnetic analysis, heat transfer and fluid flow in the Si melt. Experimental results showed good agreements with simulation data, which supports the validity of the simulation model. Based on the understanding about solution growth of SiC and our set-up, crystal growth was conducted on off-axis 4H-SiC seed crystal in the temperature range of $1600{\sim}1800^{\circ}C$. The grown layer showed good crystal quality confirmed with optical microscopy and high resolution X-ray diffraction, which also demonstrates the effectiveness of the multiphysics model to find a process condition of solution growth of SiC single crystal.

• Journal of Acupuncture Research
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• v.24 no.6
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• pp.45-61
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• 2007

Objectives : The purpose of this study is to observe the effects of Carthami Flos herbal-acupuncture (CF-HA) at Joksamni($ST_{36}$) on arthritis in mice induced by Collagen II. Methods : The author performed several experimental items, including arthritis evaluation, change in weight, spleen size and stenosis rate, change in cytokine level, IgG, IgM and anti-collagen II, change of immunocyte count and histological change of the CIA mouse joint. Conclusions are as follows: Results : 1. In the CF-HA, the arthritis index and rate and the incidence of arthritis were decreased as the experiment proceeded. 2. In the CF-HA, spleen swell and stenosis, joint edema and change were decreased. 3. In the CF-HA, the level of $IL-1{\beta}$, IL-6, $TNF-{\alpha}$ and $IFN-{\gamma}$ in blood serum were significantly decreased. 4. In the CF-HA, the level of IgG, IgM and anti-collagen II were decreased. 5. In the CF- HA, $IFN-{\gamma}$, $IFN-{\gamma}/IL-4$, IL-10 of the culture fluid was decreased. 6. In the CF-HA, the cell rate of $CD3e^+$ and $CD45R^+$, $CD4^+$ and $CD8^+$, $CD4^+/CD25^+$ in spleen was similar to the cell rate of the normal group. 7. In the CF-HA, the cell rate of $CD4^+/CD25^+$, $CD45R^+/CD69^+$ in a lymph node was decreased as in the normal group. 8. In the CF-HA, the cell rate of $CD3^+/CD69^+$, $CD11b^+/Gr-1^+$ in joints was decreased as in the normal group. 9. In the CF-HA, the cartilage destruction and the inflammation cell growth in the H&E stain were decreased. The collagen fiber in the M&T stain were less destructed, therefore the result was similar to the normal group. Conclusions : These results suggest that CH-HA at $ST_{36}$ has an effect in controlling immune reaction and suppressing inflammation in rheumatoid arthritis therefore, the continuous flow of the following study is expected.

• KIEAE Journal
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• v.17 no.1
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• pp.69-75
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• 2017

Purpose: Heat transfer analysis of recently developed 'slim type double-skin system window' were presented. This window system is designed for curtain wall type façade that main energy loss factor of recent elegant buildings. And the double skin system is the dual window system integrated with inner shading component, enclosed gap space made by two windows when both windows were closed and shading component effectively reflect and terminate solar radiation from outdoor. Usually double-skin system requires much more space than normal window systems but this development has limited by 270mm, facilitated for curtain wall façade buildings. In this study, we estimated thermophysical phenomena of our double-skin curtain wall system window with solar load conditions at the summer season. Method: A fully 3-Dimentional analysis adopted for flow and convective and radiative heat transfer. The commercial CFD package were used to model the surface to surface radiation for opaque solid region of windows' frame, transparent glass, fluid region at inside of double-skin and indoor/outdoor environments. Result: Steep angle of solar incident occur at solar summer conditions. And this steep solar ray cause direct heat absorption from outside of frame surface rather than transmitted through the glass. Moreover, reflection effect of shading unit inside at the double-skin window system was nearly disappeared because of solar incident angle. With this circumstances, double-skin window system effectively cuts the heat transfer from outdoor to indoor due to separation of air space between outdoor and indoor with inner space of double-skin window system.

• Geophysics and Geophysical Exploration
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• v.7 no.2
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• pp.109-116
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• 2004

Petroleum reservoir characterization is a process for quantitatively describing various reservoir properties in spatial variability using all the available field data. Porosity and permeability are the two fundamental reservoir properties which relate to the amount of fluid contained in a reservoir and its ability to flow. These properties have a significant impact on petroleum fields operations and reservoir management. In un-cored intervals and well of heterogeneous formation, porosity and permeability estimation from conventional well logs has a difficult and complex problem to solve by conventional statistical methods. This paper suggests an intelligent technique using fuzzy logic and neural network to determine reservoir properties from well logs. Fuzzy curve analysis based on fuzzy logics is used for selecting the best related well logs with core porosity and permeability data. Neural network is used as a nonlinear regression method to develop transformation between the selected well logs and core analysis data. The intelligent technique is demonstrated with an application to the well data in offshore Korea. The results show that this technique can make more accurate and reliable properties estimation compared with previously used methods. The intelligent technique can be utilized a powerful tool for reservoir characterization from well logs in oil and natural gas development projects.

• Korean Journal of Food Science and Technology
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• v.22 no.7
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• pp.852-857
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• 1990

The rheological properties and food functionality of the novel sugar derivatives, fructo-oligosaccharide, high maltose syrup(HMS), maltitol and sorbitol were examined and compared to those of sucrose. All samples tested showed Newtonian fluid property at the concentration range of 10% to the original concentrated products containing $69{\sim}81%w/w$ solid. HMS showed the highest viscosity. The viscosity increased(r=0.8038) as the average molecular weight of sugar derivatives were increased. The viscosity increased exponentially as the concentration increased, and sugar alcohols had lower value of the exponent compared to HMS and fructo-oligosaccharide. The viscosity of sugar derivatives solutions decreased by the increasing temperature following the Arrhenius equation. The flow activation energies of sorbitol and HMS were higer than that of sucrose. Substitution of sucrose with fructo-oligosaccharide in apple jam processing did not change the textural characteristics, but in redbean jelly(yanggaeng) it reduced the hardness, adhesiveness, springiness and cohesiveness. When sucrose was 100% replaced by HMS, the texture of apple jam and redbean jelly was not changed, but by mixing sucrose and HMS 1 : 1 ratio, the hardness decreased substantially The sugar alcohols reduced the hardness, adhesiveness, springiness of apple jam and redbean jelly significantly. Addition of fructo-oligosaccharide and HMS to sucrose did not influence the solidifying rate of candy, but sorbitol, even at 10% addition, retarded the candy moulding.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.1-11
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• 2021

POGO is a dynamic axial instability phenomenon that occurs in liquid-propelled rockets. As the natural frequencies of the fuselage and those of the propellant supply system become closer, the entire system will become unstable. To predict POGO, the propellant (oxidant and fuel) tank in the first stage is modeled as a shell element, and the remaining components, the engine and the upper part, are modeled as mass-spring, and structural analysis is performed. The transmission line model is used to predict the pressure and flow perturbation of the propellant supply system. In this paper, the closed-loop transfer function is constructed by integrating the fuselage structure and fluid modeling as described above. The pogo suppressor consists of a branch pipe and an accumulator that absorbs pressure fluctuations in a passive manner and is located in the middle of the propellant supply system. The design parameters for its design optimization to suppress the decay phenomenon are set as the diameter, length of the branch pipe, and accumulator. Multiple-objective function optimization is performed by setting the energy minimization of the closed loop transfer function in terms of to the mass of the pogo suppressor and that of the propellant as the objective function.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.107-120
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• 2021

Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.