• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.3
• /
• pp.587-592
• /
• 2008

In order to investigate the performance of an internal heat exchanger for $CO_2$ refrigerant system, the experiment was performed. Four kinds of internal heat exchangers(IHX) were used. The effects on the IHX length, the number of tube, the operating condition and the type of IHX were investigated. With increasing of the IHX length, the capacity and efficiency increased. The pressure drop of the low-side was larger compared with that of the high-side. As the temperature of the gas cooler increased, the capacity and efficiency increased linearly. The operation condition of evaporator was suggested as two phase region rather than superheat region. The capacity and efficiency of the micro-channel was larger about 90% and 75% than those of the tube. But the pressure drop of the micro-channel was more larger, compared with that of the tube.

• Food Science and Preservation
• /
• v.17 no.2
• /
• pp.281-289
• /
• 2010

We determined the optimum ethanolic conditions for extraction of $\gamma$-oryzanol and other functional components from rice bran, using response surface methodology (RSM). A central composite design was used to investigate the effects of the independent variables of solvent ratio ($X_1$), extraction temperature ($X_2$), and extraction time ($X_3$), on dependent variables including yield ($Y_1$), total phenolic content ($Y_2$), electron-donating activity ($Y_3$), ferulic acid level ($Y_4$), and $\gamma$-oryzanol concentration ($Y_5$). Solvent ratio and extraction temperature were the most important factors in extraction. The maximum yield was at 22.56 mL/g ($X_1$), 78.19C ($X_2$), and 522.15 min ($X_3$), at the saddle point. Total phenolic levels were little affected by solvent ratio or extraction temperature. The maximum concentration of extracted total phenolics was 90.78mg GAE/100 g at 21.26 mL/g, $94.65^{\circ}C$, and 567.97 min. A maximum electron-donating ability of 54.72% was obtained with the parameters 20.20 mL/g,$81.89^{\circ}C$, and 701.87 min, at the highest point. The maximum level of ferulic acid components was 210.47 mg/100g at 5.22 mL/g, $79.66^{\circ}C$, and 575.24 min. In addition, the maximum $\gamma$-oryzanol concentration was 660.39 mg/100g at 5.10 mL/g, $81.83^{\circ}C$, and 587.39 min. The optimum extraction conditions were a solvent ratio of 10.45 mL/g, $80^{\circ}C$ extraction temperature, and 535 min extraction time. Predicted extraction levels under optimized conditions were in line with experimental values.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.10
• /
• pp.8-14
• /
• 2017

Improvements in the standard of living and lifestyle have led to increased sales of frozen milk products, such as soft ice cream or slush. These frozen milk products are commonly made in a small refrigeration machine. In a soft ice cream machine, the freezer is composed of a concentric cylinder, where the refrigerant flows in the annul us and the ice cream is made in the cylinder by a rotating scraper. In this study, an optimization and performance evaluation were conducted on a soft ice cream machine having a freezer volume of 2.8 liters. The optimization was focused on the scraper rotation speed and the refrigerant path of the freezer. The measurements included the temperature, pressure and consumed power. At the optimized speed of 124 rpm, ice cream was produced in 6 minutes and 2 seconds, and the COP was 0.90. Through a flow visualization study using air-water, the refrigerant path was improved. The improved design reduced the ice cream making time significantly. The present results may be used for the optimization of other refrigeration cycles, including those of frozen food products.

• Journal of Energy Engineering
• /
• v.24 no.4
• /
• pp.140-145
• /
• 2015

This study was aimed at analyzing NOx conversion characteristics in the HC-SCR with biodiesel content changes of the secondary fuel injection (BD0, BD10, BD25). Test conditions for temperature were set to $290^{\circ}C$, $320^{\circ}C$ and $350^{\circ}C$ considering the upstream temperature of a HC-SCR, distillation of the secondary injected fuels and etc. The amount of fuel injection was adjusted with a fixed space velocity of 55,000(1/h). According to the test results of distillation, the T90 was the same level about $350^{\circ}C$ on all test fuels and the amount of evaporation was reduced at lower than $350^{\circ}C$ temperature condition with increasing biodiesel content. As biodiesel content which is mixed with the secondary injected fuel is increased, NOx reduction efficiency was determined to decrease. The difference of the Nox reduction ratio in a high temperature condition($320^{\circ}C$ and $350^{\circ}C$) than the low temperature($290^{\circ}C$) was more significant. These results are thought to be poor evaporation properties (distillation) and high molecular weight of the biodiesel.

• Journal of Korea Water Resources Association
• /
• v.50 no.12
• /
• pp.837-847
• /
• 2017

Land Surface Model (LSM) was developed for the Soyang river basin located in Korean Peninsula to clarify the spatio-temporal variability of hydrological weather parameters. Variable Infiltration Capacity (VIC) model was used as a LSM. The spatial resolution of the model was 10 km and the time resolution was 1 day. Based on the daily flow data from 2007 to 2010, the 7 parameters of the model were calibrated using the Isolated Particle Swarm Optimization algorithm and the model was verified using the daily flow data from 2011 to 2014. The model showed a Nash-Sutcliffe Coefficient of 0.90 and a correlation coefficient of 0.95 for both calibration and validation periods. The hydrometeorological variables estimated for the Soyang river basin reflected well the seasonal characteristics of summer rainfall concentration, the change of short and shortwave radiation due to temperature change, the change of surface temperature, the evaporation and vegetation increase in the cover layer, and the corresponding change in total evapotranspiration. The model soil moisture data was compared with in-situ soil moisture data. The slope of the trend line relating the two data was 1.087 and correlation coefficient was 0.723 for the Spring, Summer and Fall season. The result of this study suggests that the LSM can be used as a powerful tool in developing precise and efficient water resources plans by providing accurate understanding on the spatio-temporal variation of hydrometeorological variables.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.42 no.10
• /
• pp.1664-1672
• /
• 2013

Solar salt is manufactured naturally, and therefore, it contains insoluble substances such as sandy compounds. This study is performed in order to effectively produce clean sea salt by removing the impurities in sea salt through filtration and evaporation in a vacuum condition. Brine was concentrated and crystallized at $90^{\circ}C$ by a rotary vacuum evaporator, which was then recovered as salt crystals by filtration, and then the salt was dehydrated. Manufacturing yields were determined by the amount of water evaporation. Brine was concentrated to 40%, 50% and 60% of the initial volume of brine and manufactured salt were designated as 40S, 50S and 60S, respectively. The salt produced by this process is called ESBS (evaporated salt with brine from salt-farm). The yield of 40S, 50S and 60S were 7.22%, 10.79% and 15.06%, respectively. The NaCl concentration of 40S and 50S were 90.38% and 91.16%, respectively. From a sensory evaluation analysis, the most tasty salt was 40S and the bitter salt was 60S. The average contents of sand compound and insoluble substances in ESBS were 0.001~0.012% and 0.067~0.12%, respectively. The mineral compositions, such as Na, Mg, K, and Ca of 40S and 50S were similar with those of the natural solar salt. In solubility tests, the solubility (g of salt/100 mL $H_2O$/sec) of 40S, 50S, and 60S was 0.69, 0.70, and 0.69, respectively. On the other hand, the solubility of natural solar salt was 0.47. By comparing the water reabsorption rate analysis results, water reabsorption rate of 40S and 50S was about 3 to 5 times lower than that of the solar salt. In the aspects of physical and chemical properties, such as minerals, impurities, solubility and moisture re-absorption rate, salts developed in this study are judged to be better than that of the general solar salt.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.150-150
• /
• 1999

재료의 광학적 특성을 변화시키기 위한 표면 코팅의 사용을 잘 알려져 있다. 그리고 이러한 광학 코팅은 우리가 주위에서 볼 수 있는 렌즈에서부터 레이저반사경 다 나아가 다양한 광학 필터에 이르기까지 빛의 간섭을 이용한 광학 박막의 코팅은 폭넓게 이용되고 있다. 그러한 응용가운데 불필요한 표면 반사를 방지함으로써 전체 투과율을 강화시키기 위한 무반사(Anti-Reflection) 코팅은 오늘날 광대역 무반사 특성 등 다양한 광학적 요구에 따라 하나 또는 그 이상의 층을 형성함으로써 극적으로 성취할 수 있다. 본 실험은 기존 많이 활용되는 증발법 그리고 스퍼터링 방법과는 달리 고진공하에서 증착 변수를 효과적으로 제어, 박막을 형성할 수 있는 자체 제작된 단일 IBS(Ion Beam Sputtering) 시스템을 이용하여 우수한 광학적 특성을 갖는 광학 재료로써 무반사용 다층박막 형성하기 앞서 MgF2, ZrO2 (yttria stabilized zirconia) 단층 박막을 제조하였으며, 각 증착 변수에 따른 결정학적 및 광학적 특성을 관찰하였다. 본 실험에 사용된 제조 장비로 Kaufman type 2.5inch의 이온 건이 장착된 Ion Beam sputtering 시스템으로 초기 진공도는 5$\times$10-6orr이며, 이온 빔의 전류 밀도는 Fareday cup을 이용했다. 6inch 크기의 ZrO2(yttria stabilized zirconia), MgF2 타겟트를 이용하여 Si(100), glass 기판위에 박막을 성장시켰다. 각 타겟트에 대한 증착변수로 이온 에너지, 기판온도, Ar 가스량을 변화시키면서 박막을 제조하였다. 제조된 박막의 광학적 특성으로 가시 영역에서 투과율의 변화는 자외/가시광선 분광 분석기 (UV/VIS specrophotometer)를 이용하여 측정했다. 그리고 박막의 조성 및 결정학적 구조는 AES EDS와 XRD로 확인하였다. 이온 빔 전압 500V, 빔 저류 55mA일 때 온도는 상온에서 30$0^{\circ}C$까지 승온 후 MgF2 박막의 XRD분석결과 우세한 결정성을 관찰할 수 없었으며, 이 때의 광 투과도는 가시영역에서 80~90%의 값으로 측정되었다. 추후 증착된 막의 결정성을 위해 열처리를 실시하고, 각 증착조건에 대한 결과는 학회 발표시 보고한다.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.34 no.7
• /
• pp.1035-1040
• /
• 2005

This study was conducted to investigate the surface spraying effect of materials on the rheological properties of frozen starch with microwave heating. Microwave helps reduce cooking time by high temperature, but swiftly snatches moisture from foods such as frozen starches (buns and noodles etc) and makes surface of foods harder. Four types of maltodextrin materials have been prepared for different concentration solutions and sprayed on surface doughs of sheet type. Sprayed dough samples were Quickly frozen at $-70^{\circ}C$ and wrapped with polypropylene film. All the treated samples were kept at 0, -20 and $-50^{\circ}C$, and then taken out periodically for measurement of the quality during storage. The quality attributes evaluated after heating with microwave energy include sensory quality retrogradation, texture, surface color and microstructure. The quality of frozen starches deteriorated with long term storage even at low temperatures of -20 and $-50^{\circ}C$, and the spray materials were found to improve the textural and physical properties of frozen starches in the microwave heating. Particularly, maltodextrin with D.E value of $9\~12$ had the most desirable effects of quality improvement.

• Journal of Animal Environmental Science
• /
• v.16 no.3
• /
• pp.237-244
• /
• 2010

Using a vertical composting system in layer farms, the composting process was characterized in terms of temperature variation, change of moisture contents, fertilizer ingredient and so on. In this study, two types of layer farms were examined. The layer manure was produced as 3,300 and 116,650 kg/day for Farm A and Farm B, respectively. Also, their average moisture contents were 74.4% (Farm A) and 65.6 % (Farm B). The inside temperature of composting in Farm A was varied in the range of 50 to $70^{\circ}C$, and moisture content of it decreased from 59.5% to 20.6% at the edge of vertical composting system. While in Farm B, composting temperature was fluctuated between 50 and $65^{\circ}C$ and moisture content declined from 34.0% to 13.4% at the end of vertical composting system. The fertilizer ingredients such as T-N, $P_2O_5$ and $K_2O$ were not significantly influenced by seasonal effect. Their values were changed in the range of 0.90% to 0.47% for T-N, 0.16% to 0.42% for $P_2O_5$, and 0.22% to 0.28 for $K_2O$, respectively. Also, OM/N ratio was varied from 36.8 to 84.4.

• Korean Journal of Food Science and Technology
• /
• v.32 no.1
• /
• pp.90-96
• /
• 2000

The optimum cooking conditions for large scale continuous gas cooker were studied with three varieties of rice. Optimum soaking time for the cooker was estimated to be 30 min at cooking temperature above $20{\circ}C$, while 60 min at cooking temperature below $10{\circ}C$. The ratio of water-to-milled rice giving the best eating quality was founded to be $1.41{\sim}1.48$, and corresponding moisture content of cooked rice ranged from 60 to 62% for different rice varieties. The optimum ratio of water to milled rice. (Chucheong) decreased from 1.50 to 1.37 with increase in the amount of milled rice from 4.0 to 6.5 kg in a cooking vessel. However, actual water uptake by rice (g water absorbed per g rice) on cooking was nearly constant value of 1.13, which means that evaporated water during cooking increases with decreasing the amount of rice in a cooking vessel.