• Corrosion Science and Technology
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• 제14권2호
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• pp.47-53
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• 2015

Recently, the bending process is greatly applied to fabricate the pipe line. Bending process can reduce welding joints and then decrease the number of inspection. Thus, the maintenance cost will be reduced. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. By this thermal process, corrosion properties and microstructure can be affected. This work focused on the effect of induction heating bending process on the properties of ASME SA106 Gr. C low carbon steel pipes. Microstructure analysis, hardness measurements, and immersion corrosion test were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. Hardness was measured using a Rockwell B scale. Induction heat bending process has influenced upon the size and distribution of ferrite and pearlite phases which were transformed into finer structure than those of base metal. Even though the fine microstructure, every bent area showed a little lower hardness than that of base metal. It is considered that softening by the bending process may be arisen. Except of I2, intrados area, the others showed a similar corrosion rate to that of base metal. But even relatively high rate of intrados area was very low and acceptable. Therefore, it is judged that induction heat bending process didn't affect boric acid corrosion behaviour of carbon steel.

• 설비공학논문집
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• 제22권12호
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• pp.837-844
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• 2010

In this study, performance of R1234yf and R1234yf/R134a mixture is measured on a heat pump bench tester in an attempt to substitute R134a used widely in mobile air conditioners (MACs). The bench tester is equipped with a open type compressor providing a nominal capacity of 3.5 kW. All tests are conducted under the summer cooling and winter heating conditions of 7/4 $5^{\circ}C$ and $-7/41^{\circ}C$ in the evaporator and condenser, respectively. For R1234yf/R134a mixture, measurements are made at 5%, 10%, and 15% of R134a by mass. Test results show that the coefficient of performance (COP) and capacity of R1234yf are up to 2.7% and 4.0% lower than those of R134a, respectively. For R1234yf/R134a mixture, the COP and capacity are up to 3.9% lower and 3.6% higher than those of R134a. For R1234yf and R1234yf/R134a mixture, the compressor discharge temperature is $4.1{\sim}6.7^{\circ}C$ lower than that of R134a while the amount of charge is reduced up to 11% as compared to R134a. 90%R1234yf/10%R134a is a better refrigerant than pure R1234yf in that it is less flammable and more compatible with existing R134a system. Based upon the results, it is concluded that R1234yf and R1234yf/R134a mixture are long term environmentally friendly solutions to mobile air-conditioners due to their excellent environmental properties with acceptable performance.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3538-3548
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• 1996

In this study, as a part of basic study for developing the simulation program for the assemssment of reliability of electronic EMC packaging which covers from EMC mixing step to thermal analysis, comparison between a measured and predicted values of material properties of EMC and finitde element analysis of thermal stress are performed. For the experimental testing specimens of fifty, sixty hive and eighty percent filler($13\mu m$, spherical silica) weight fraction are fabricated using tranfer molding. Coefficient of thermal expansion, elastic modulus and thermla conductivity are measured using these specimens and then these measured values are compared with the predicted values by various equations ( such as dilute suspension method. self consistent method, generalized self consistent method, Hashin-Shtrikman's bounds. Shapery's bounds, Nielsen's method and others). Measured values are distributed within the upper and lower bounds of equations. Measured elastic modulus and coefficient of thermal expansion approaches closely the perdicted values with self consisten mehtod and upper bound of Shaperys equation respectively. However small differences of thermal conductivity between the different filler volume fraction are obserbed. FEM analysis indicates that firstly stress is concentrated at the corner section of EMC and secondly EMC with eighty percent filler weight fraction shows less thermal stress when package is cooling down and relatively high thermal stress when package is heating up.

• 한국지열·수열에너지학회논문집
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• 제10권1호
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• pp.7-13
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• 2014

This study intends to analyse the economical aspect of a GSHP(Ground Source Heat Pump) system compared to the conventional system which is consisted with a boiler and a chiller. This study has simulated four systems in Incheon. It developed and analyzed for applications in a residential and an office building which was based on the hourly EPI(Energy Performance Index, $kWh/m^2yr$). Case 1 is utilizing a boiler and a chiller to meet heating and cooling demand of a house. Case 2 is utilizing the same conventional set up as Case 1 of a office. Case 3 is summation of Case 1(house) and 2(office) systems and loads. And Case 4 is utilizing a GSHP to meet the combined loads of the house and office. The method of the economic assessment has been based on IEA ECBCS Annex 54 Subtask-C SPB(Simple Payback) method. The SPB calculated the economic balanced year of the alternative system over the reference system. The SPB of the alternative systems (GSHP) with 10%, 30% and 50% initial incentive has been calculated as 9.38, 6.72 and 4.06 year respectively while the SPB without initial incentive of systems was 10.71 year.

• 태양에너지
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• 제18권3호
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• pp.197-203
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• 1998

A 5 ton/day pilot scale two-phase anaerobic digester was constructed and tasted to treat Korean food wastes in Anyang city. The process was developed based on 3 years of lab-scale experimental results on am optimim treatment method for the recovery of biogas and humus. Problems related to food waste are ever Increasing quantity among municipal solid wastes(MSW) and high moisture and salt contents. Thus our food waste produces large amounts of leachate and bed odor in landfill sites which are being exhausted. The easily degradable presorted food waste was efficiently treated in the two-phase anaerobic digestion process. The waste contained in plastic bags was shredded and then screened for the removal of inert material such as fabrics and plastics, and subsequently put into the two-stage reactors. Heavy and light inerts such as bones, shells, spoons and plastic pieces were again removed by gravity differences. The residual organic component was effectively hydrolyzed and acidified in the first reactor with 5 days space time at pH of about 6.5. The second, methanization reactor part of which is filled with anaerobic fillters, converted the acids into methane with pH between 7.4 to 7.8. The space time for the second reactor was 15 days. The effluent from the second reactor was recycled to the first reactor to provide alkalinities. The process showed stable steady state operation with the maximum organic rate of 7.9 $kgVS/m^3day$ and the volatile solid reduction efficiency of about 70%. The total of 3.6 tons presorted MSW containing 2.9 tons of food organic was treated to produce about $230m^3$ of biogas with 70% of methane and 80kg humus. This process is extended to full scale treating 15 tons of food waste a day in Euiwang city and the produced biogas is utilized for the heating/cooling of adjacent buildings.

• 토지주택연구
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• 제11권1호
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• pp.87-94
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• 2020

To implement the planning of zero-energy buildings, their energy performance must be improved, and renewable energy applications must also be included. To accelerate the use of renewable energies in such buildings, BIPVs should be actively used in windows and on roofs. Window-type BIPVs are being developed in various forms depending on the size, composition, area ratio of the window, specification of glass, and so on. To analyze the applicability of various solar cells as window-type BIPVs, in this study, we evaluated their applicability, at the current development level, by analyzing the indoor illuminance, heat gain and heat loss; the cooling, heating, and lighting energy levels; and the generation performance of the various solar cells. To enhance the future applicability of window type BIPV, we analyze the overall energy performance of the building, according to changes in visible light transmittance and generation efficiency. The main research results are as follows. The area ratios above the standard illuminance, based on the window type and according to the VLT, were in order of low-e glazing, a-Si window, DSSC window, and c-Si window. The heat gain of the semi-transparent solar cell winodw was remarkably low. The energy consumption of buildings was highest in the order of c-Si window, DSSC window, a-Si window, and clear low-e window. However, in the case of including the power generation performance of the solar cell, the energy consumption was found to be high in order of DSSC window, c-Si window, a-Si window, and clear low-e window. In the future, if a window-type BIPV is developed, we believe that improvement in power generation performance and improvement in visible light transmittance will be needed.

• 한국표면공학회지
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• 제56권4호
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• pp.233-242
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• 2023

In recent years, energy-management studies in buildings have proven useful for energy savings. Typically, during heating and cooling, the energy from a given building is lost through its windows. Generally, to block the entry of ultraviolet (UV) and infrared (IR) rays, thin films of deposited metals or metal oxides are used, and the blocking of UV and IR rays by these thin films depends on the materials deposited on them. Therefore, by controlling the thicknesses and densities of the thin films, improving the transmittance of visible light and the blocking of heat rays such as UV and IR may be possible. Such improvements can be realized not only by changing the two-dimensional thin films but also by altering the zero-dimensional (0-D) nanostructures deposited on the films. In this study, 0-D nanoparticles were synthesized using a sol -gel procedure. The synthesized nanoparticles were deposited as deep coatings on polymer and glass substrates. Through spectral analysis in the UV-visible (vis) region, thin-film layers of deposited zinc oxide nanoparticles blocked >95 % of UV rays. For high transmittance in the visible-light region and low transmittance in the IR and UV regions, hybrid multiple layers of silica nanoparticles, zinc oxide particles, and fluorine-doped tin oxide nanoparticles were formed on glass and polymer substrates. Spectrophotometry in the UV-vis-near-IR regions revealed that the substrates prevented heat loss well. The glass and polymer substrates achieved transmittance values of 80 % in the visible-light region, 50 % to 60 % in the IR region, and 90 % in the UV region.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.201.2-201.2
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• 2011

A water-source heat pump system has been developed for cooling and heating of a green house on the waterfront in Jinju. In order to supply a heat source/sink of water in alluvium aquifer to the heat pump system, the riverbank filtration facility (two pumping wells and one recharge well) for water intake and injection has been constructed. To pump and recharge water sufficiently, the geometric design such as depth and diameter for the wells have been completed, and details of the well such as slot size and length of the screen and filter pack size have been designed based on the practical and theoretical design method including D30 technique. For the investigation of the hydrogeological characteristics, step-drawdown test, long-term pumping test, and recovery test have been carried out for two developed pumping wells. Step-drawdown test has been performed on 4 step flowrates of 150, 300, 450, $600m^3$/day for 1 hour, and long-term pumping test on flowrate of $500m^3$/day for 24 hours, and recovery test for 6 hours. Since the underground water filtrated by riverbank is flowing smoothly into the well, the water level goes down slightly for the long-term test. Consequently, the stable pumping flowrate for two pumping well has been predicted at least over $1,647m^3$/day which is larger than the flowrate of $1,000m^3$/day for a 60 RT heat pump system.

• Nutrition Research and Practice
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• 제6권1호
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• pp.16-20
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• 2012

The effects of retrograded rice on body weight gain, gut functions, and hypolipidemic actions in rats were examined. When the retrograded rice was produced by repetitive heating and cooling cycles, it contained significantly higher amounts of resistant starch ($13.9{\pm}0.98%$) than is found in common rice ($9.1{\pm}1.02%$) (P < 0.05). Sprague-Dawley rats were fed either common rice powder or retrograded rice powder, and mean body weight gain was significantly lower in the retrograded rice group (P < 0.05). The liver weight of the retrograded rice group ($14.5{\pm}0.5\;g$) was significantly lower than that of the common rice group ($17.1{\pm}0.3\;g$, P < 0.05). However, the weights of other organs, such as the kidney, spleen, thymus, and epididymal fat pad were not significantly affected by rice feeding. Intestinal transit time tended to be lower in rats fed retrograded rice when compared to rats fed the common rice, but the difference was not significant. The retrograded rice diet significantly increased stool output when compared to that in the common rice powder diet (P < 0.05), whereas fecal moisture content (%) was significantly higher in the retrograded rice group ($23.3{\pm}1.2$) than that in the common rice group ($19.1{\pm}1.2$) (P < 0.05). The retrograded rice group had significantly lower plasma cholesterol (P < 0.05), liver cholesterol (P < 0.05), and triacylglycerol contents in adipose tissue (P < 0.05) when compared to those in the common rice group. In conclusion, retrograded rice had higher resistant starch levels compared with those of common rice powder, and it lowered body weight gain and improved lipid profiles and gut function in rats.

• 한국결정성장학회지
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• 제20권2호
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• pp.101-105
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• 2010

플라즈마 에쳐 내에 사용되는 실리콘 전극과 링 부품은 사용 중에 강한 플라즈마와 접촉하면서 주기적인 가열과 냉각 과정을 거친다. 이 때 부품의 표면에서는 열 응력으로 인하여 PSB라고 하는 띠 형상의 결함이 생성되며 이로 인하여 그 수명을 다하게 된다. 원료인 실리콘 잉곳의 관점에서 그 수명에 미치는 인자를 살펴보았다. 잉곳의 등급, 즉 S/F와 S/A에 따라 불순물과 결함의 농도를 GDMS와 ${\mu}$-PCD로 평가하여 잉곳의 어떤 요소들에 의하여 수명이 결정되는가를 분석하였다. 그 결과, {001} 면상에서 관찰되는 <110> 방향의 면 결함들이 PSB와 연결될 가능성이 있음을 제안하였다.