• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.517-522
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• 2013

Small size ice-cream maker has two evaporators having different evaporating temperatures of $4^{\circ}C$ and $-8^{\circ}C$. In such case, ice-cream maker system design becomes complicated because multiple capillary tubes affects one another. In this study, performance analysis was conducted for the soft ice-cream maker having two evaporators operating at different temperatures. The compressor was analyzed using efficiency models, the capillary tube was modeled assuming one-dimensional flow, the condenser and the evaporators were modeld based on UA-LMTD method. The refrigeration cycle simulation program was developed applying the enthalpy, pressure and mass balance on each component. Comparison of the test data with the simulated results for R404A revealed that evaporator temperatures of refrigerator and freezer agreed within $3^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2565-2571
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• 2009

In this paper, cycle performance analysis of cascade refrigeration system using $NH_3-CO_2$(R717-R744) is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree and condensing and evaporating temperature in the ammonia(R717) high temperature cycle and the carbon dioxide low temperature cycle. The COP of cascade refrigeration system increases with the increasing superheating degree, but decreases with the increasing subcooling degree. The COP of cascade refrigeration system increases with the increasing condensing temperature, but decreases with the increasing evaporating temperature. Therefore, superheating and subcoolng degree, evaporating and condensing temperature of cascade refrigeration system using $NH_3-CO_2$ have an effect on the COP of this system. A multilinear regression analysis was employed in terms of subcooling, superheating, evaporating, condensing, and cascade heat exchanger temperature difference in order to develop mathematical expressions for maximum COP and an optimum evaporating temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3327-3335
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• 2014

In this study, comparison works have been performed for single-stage and multi-stage refrigeration cycle using propane as a refrigerant in order to cool down the natural gas stream. A comparative analysis has been performed for a single, two, three and four stage refrigeration cycle using propane as a refrigerant for cooling the natural gas stream. For the simulation, natural gas feedstock properties supplied by KOGAS were utilized and Peng-Robinson equation of state model was used. As the number of compression stages increase, the condenser heat duty is decreased. The refrigeration heat duty for a four-stage refrigeration cycle is decreased by 20.36% compared to that for a single-stage refrigeration cycle. Moreover, the total refrigerant circulation rate for a four-stage refrigeration system is was reduced by 14.53% compared to the single stage refrigeration cycle. The total compression power for a four-stage compression was reduced by 41.61% compared to the single stage compression.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.197-201
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• 2006

Long-term storage technology was developed to extend shelf-life of citron (Citrus junos). Changes in quality characteristics of blanched and frozen citron peels (type A, without blanching for control; type B, blanched at $95^{\circ}C$ for 2 min; type C, blanched at $95^{\circ}C$ for 2 min, sugar added; type D, blanched at $95^{\circ}C$ for 5 min) during frozen storage were evaluated. Citron jam was prepared using frozen citron sample B, which showed the highest quality characteristics during storage, and high quality characteristics, such as yield and overall acceptability, were obtained when using 40% frozen citron, 41% sugar, 18.56% glutinous starch syrup, 0.39% pectin, and 0.05% citric acid. During storage of both blanched and frozen citron peels and citron jam made of frozen citron peel, changes in characteristics such as pH, total acids, soluble solids, and browning, were lower than those of control. Sensory evaluation for sourness, sweetness, and overall acceptability of citron jam made with frozen citron peel during storage showed higher values than those of control.

• 농업기술회보
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• v.42 no.7 s.501
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• pp.34-37
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• 2005

쌀협상 비준동의안 상정 또 연기...언론 '경제의 짐' 우려/대법원, 우리 농산물 학교급식 지원 조례 위법판결 파문/APEC 미 대표 "한-미 포괄적 FTA체결해야"/'조류인플루엔자'대책 시급하다'/ '중국산 냉동고추' 변칙수입 차단하라/광주전남농민연대 투쟁 선포 기자회견문

• Bulletin of Food Technology
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• v.25 no.2
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• pp.116-128
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• 2012

식품동결에 의한 품질손상에 있어 크게 영향을 미치는 인자 중의 하나가 체적변화에 의한 조직 파괴이므로 식육 및 과채류의 냉동시 내부압력에 따른 조직파괴를 방지하기 위한 기초연구로 다양한 동결방법에 따른 내부압력 변화에 대하여 조사한 결과, 급속 및 완만동결시 우육의 내부압력 변화 경향은 동결 직전에 급격히 상승한 후 동결 초기부터 최대빙결정생성대를 통과하는 동안은 급격히 감소하다가 다시 온도가 내려감에 따라 압력변화는 증가와 감소를 반복하여 상승하는 경향을 보여 주었고, 동결시의 내부압력 크기는 약 8~10 psig 수준이며, 내부압력의 변화 경향은 정지공기식보다 침지식에서 약 1 psig 정도 크게 나타났다. 냉동냉장시에 일어나는 내부압력의 상하변화는 돈육의 품온차가 ${\pm}1^{\circ}C$일 때, 시료중량에 따라 1.84~2.32 psig 정도의 내부압력 차가 반복적으로 발생됨을 알 수 있었다. 또한, 돈육의 해동시 내부압력은 해동 개시 후 급격히 상승하여 5분 이내에 최고압력에 도달한 이후에는 서서히 하강하였으며, 해동시에 발생한 내부압력의 값은 동결시의 내부압력 값보다도 대부분 크게 나타났다. 또한, 균온처리한 우육의 동결시 내부압력 값은 약 1~4 psig 수준으로 균온처리하지 않은 우육에 비하여 매우 적게 나타났으며, 동결소요시간도 약 10~20% 정도 짧게 나타났다. 그리고 균온처리 및 다양한 동결방법에 따른 동결식육의 조직과 냉동냉장 중의 품질변화를 비교 검토한 결과, 동결방법에 따른 드립손실율은 우육의 경우 정지공기식으로 처리한 시료는 타 처리구에 비해 계속 높게 나타났으며, 돈육은 우육에 비해 상대적으로 드립손실량이 적게 나타났으나 송풍식으로 처리한 시료에서 저장 40일째, 7.39%로 가장 높게 나타났다. 동결 우육 및 돈육의 pH변화는 뚜렷한 차이를 나타내지 않았으며, VBN 및 TBA값에 있어서는 균온 처리한 시료가 완만 및 급속동결 처리한 타 시료에 비해 저장 200일까지 가장 변화가 없었다. 동결저장온도의 상하변동에 있어서는 온도변동 횟수가 증가할수록 pH 및 수분함량은 뚜렷한 변화가 없었으나 드립손실율, VBN 및 TBA값은 온도 변동횟수가 증가할수록 서서히 증가하는 경향을 보여 주었다.

• Journal of the Korea Society of Computer and Information
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• v.12 no.5
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• pp.321-326
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• 2007

The contents of reef container face a risk of being damaged if the interior temperature and certain maintenance conditions for the shipments cannot be met. Currently, the temperature and other conditions within a reefer container is checked manually and periodically by someone in charge of it. Since it means that there is no real-time checking of the conditions, if something goes wrong, there is no immediate means of correcting the problem. This paper introduces reefer container monitoring system, that checks interior temperature of container on real-time by sensor nodes attaching reefer container using wireless sensor network. It senses the temperature, amount of light, motion and the change in speed of the objects that distributes sensors throughout the desired places and sends the data wirelessly to anyone interested. Because the prosed technique can check the temperature and other conditions within a reefer container on real-time basis, it enables efficient and effective maintenance of temperature and other conditions

• Journal of Institute of Convergence Technology
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• v.1 no.2
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• pp.29-32
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• 2011

In this paper, we will introduce the overview of new project dealing how to increase of refrigeration cycle COP using nano-fluids, CuO, TiO2, Al2O3, that are used on similar previous studies. Recently many studies were performed to show the effect of nano-fluids at refrigeration cycle. But, the reason was not cleared yet. In general, the flow phenomena at the evaporator were guessed to be mixed with the partial pool boiling condition and the flow boiling condition from the previous results not published yet. So, we hope that the COP increase of refrigeration cycle will be verified and showed through this project.

• Journal of the KSME
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• v.29 no.4
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• pp.394-402
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• 1989

열전달 분야 중에서도 대류열전달에 관련된 수치해석적 연구가 현재 국제적으로 많은 연구의 대상이 되고 있으므로 이번 기회에 국내에서 수치적 방법을 이용한 대류열전달 분야의 연구동 향을 간략히 기술하고자 한다. 대류열전달 분야를 소분류하는 방법에는 여러 가지가 있겠으나 이번 조사에서는 "자연대류 열전달", "강제대류 열전달" 그리고 "상변화 열전달"의 세 가지로 분 류하였으며 위의 분류에 명확히 속하지 않는 것이라고 유사성을 참고하여 분류하였다. 상기 각 분야에서의 기술 순서는 대략적으로 발표년도 순서를 따랐다. 본 연구동향의 조사에서는 국내 학술 문헌중 "대한기계학회논문집"을 중심으로 하여 이외에 관련된 학술지로서 "공기조화. 냉동 공학", "태양에너지"등에 수록된 논문을 발췌 요약하였다.uot;공기조화. 냉동 공학", "태양에너지"등에 수록된 논문을 발췌 요약하였다.된 논문을 발췌 요약하였다.

• Journal of Industrial Technology
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• v.34
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• pp.21-26
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• 2014

The effect of refrigerant R-134a and R-430a on the performance of refrigeration equipment for R-134a is investigated. Refrigeration effect, compression work and coefficient of performance of refrigeration equpment for both R-134a and R-430a are obtained by experimentation. These performances comparison between R-134a and R-430a is made in case of the maximum load. Refrigeration effect for R-134a and that for R-430a is almost equal while compression work for R-134a is less than that for R-430a. Consequently it shows that coefficient of performance for R-134a is relatively 11% higher than that for R-430a.