In this study, we investigated the effects of cooling rate during storage on spring kimchi cabbage from an economic perspective. For long-term storage, kimchi cabbage (KC) should be maintained at a low temperature immediately after harvest; however, a sudden change in temperature during storage may lead to chilling injury in KC. The optimal cooling rate is important for the long-term storage of KC. To identify the optimal cooling rate, KC was cooled at different cooling rates (1oC, 2oC, 4oC, 6oC, 8oC, and 24 oC/day), and then stored at 1oC for 90 days. Thereafter, weight, trimming, total loss, pH, free sugar content, and total bacterial count changes were measured. Spring KC stored at the cooling rate of 6 oC/day presented a lower total loss and better sensory properties than KC stored at other cooling rates; thus, 6 oC/day is an appropriate cooling rate for long-term storage of KC.

통영 LNG 기지에서 방류되는 냉배수가 진해만에 미치는 영향을 알아보고, 냉배수의 활용 방안 모색을 위해 총 4개의 냉배수 방류량에 대한 진해만의 환경변화를 1년간(2018년) 모의하였다. 실제 냉배수 방류량인 Case1(10 m3 sec-1)의 모의 결과, 모든 분기에서 냉배 수에 의한 진해만의 환경변화는 매우 미미하게 나타났다. 모의 방류량인 Case2(100 m3 sec-1)의 경우 방류구 반경 5 km 범위에서 1 ~ 3℃의 수온 감소를 보였으며, Case3(1000 m3 sec-1)에서는 방류구 반경 8 km 범위에서 최대 4 ~ 5℃의 수온이 감소하였고 진해만 전 해역에 걸쳐 냉 배수가 확산하는 결과를 보였다. 플랑크톤의 성장 속도는 최대 15% 감소하였으며(11월), 대형조류의 성장 속도는 행암만 부근에서 최대 6 % 증가하는 결과를 보였다. 상기 결과로부터 통영 LNG 기지에서 방류되는 냉배수에 의한 진해만의 환경변화는 미미한 것을 확인하였 다. 또한 Case3 결과로부터 국소지역의 ‘적조 방재’, ‘해조류 성장’을 목적으로 냉배수의 활용이 가능할 것으로 기대된다.

PURPOSES : The cooling characteristics of the asphalt mixture in a moving dump truck were analyzed using a numerical simulation method. The cooling characteristic can be used to determine the optimum transport path for minimizing the temperature drop of the asphalt mixture. METHODS : In this research, a coupled analysis of the discrete element method (DEM) with computational fluid dynamics (CFD) was applied for cooling characteristic analysis of asphalt mixtures in transit. Two different transit speeds, 30 km/h and 60 km/h, were considered to evaluate the effect of speed on the temperature drop of the asphalt mixture. Velocity, pressure, and temperature contours were plotted and temperature variations were compared. RESULTS : Most of the temperature drops in the asphalt mixture were observed in the middle of the dump box in the longitudinal direction. It was confirmed that a faster speed causes a greater temperature drop for the same travel time and a slower speed causes the more temperature to reach the same travel distance as expected. CONCLUSIONS : It is concluded that the coupled analysis method can be used to quantitatively evaluate the effect of vehicle speed on temperature drop in asphalt mixtures. In addition, the method can be used to determine the optimum travel path considering environmental conditions and traffic congestion.

The new thermal management models of linear compressors have been recently reported. These models adopt the simplified transient flow effects to shorten the excessive analysis time. Among the unsteady flow effects of the linear compressor, the effect of the gap flow between the compressor housing and the body due to the body vibration on the heat transfer performance was studied in this paper. For this study, a numerical analysis for the unsteady axisymmetric flows was performed by using CFD (Computational Fluid Dynamics). The results show that the high-speed refrigerant flows occurred in the gap between the compressor housing and the body, which contribute to increasing the heat transfer from high temperature refrigerants in the housing to the outside air. In addition, as the gap decreases, the refrigerant flow rate through the gap increases and the heat transfer rate increases as well.

In this study, the cooling performance of the motor was analyzed according to the number and the length of the fins of the heat sink, and at the same time, the effect of forced convection on the cooling performance improvement by changing the air flow speed of the cooling fan was conducted. In order to find out the cooling performance in terms of turbulent kinetic energy, pressure, and temperature according to the number of heat sink fins, length of fins, and wind speed of the cooling fan, an aluminum heat sink was modeled according to the size of the motor. The heating value of the motor was calculated, and it was set to be the same under all analysis conditions. The turbulence model applied for numerical analysis in this study used the standard k-ε model. As a result, it was confirmed that the cooling effect of the heat sink increases as the air flow speed of the cooling fan, the number of fins, and the length of fins increase.

The longest process in the injection molding process is the cooling process of the molded product. Therefore, shortening the cooling time is key to reducing the injection molding cycle time. For fast cooling time, the production of conformal cooling channels using metal 3D printing instead of the conventional linear cooling channels is continuously increasing. In this study, the cooling effect of the conventional linear cooling channel application and the conformal cooling channel application using metal 3D printing was compared in the design of the back cover molding mold of the circulator that has been widely used recently. The comparison of the cooling effect was based on the mold temperature and the molded product temperature for a certain period of time after completion of molding. It was confirmed that the time required to eject from the mold with the conformal cooling channel to the ejecting temperature of the molded product was reduced by 28.7%, and the maximum temperature of the mold was also reduced by 40%.

The effect of flow direction on heat transfer in water cooling channel of lithium-ion battery is numerically investigated. Battery Design StudioⓇ software is used for modeling electro-chemical heat generation in the battery and the conjugated heat transfer is analyzed with the commercial package STAR-CCM+. The result shows that the maximum temperature and temperature difference of battery with Type 1 are the lowest because the heat transfer in the entrance region near the electrode is enhanced. As the inlet velocity is increased, the maximum temperature and temperature difference of battery decreases but the pressure loss increases. The pressure loss in Type 2 channel is the lowest due to the shortest channel length, while the pressure loss with Type 3 or 4 channel is the highest because of the longest channel length. Considering heat transfer performance and pressure loss, Type 1 is the best cooling channel.

Spring kimchi cabbage was stored fresh for 90 days in a commercial cold storage house. It was sanitized by spraying fungicide on the field before harvesting. The plastic boxes of spring kimchi cabbage were put on the pallet, covered with a 40-hole film, then stacked in the cold storage room at once. The room was maintained for 90 days at 0.7oC after cooling gradually at 2 oC/day. After 90 days, the weight loss was 4.73% and the total trimming loss was 8.26%. The weight loss was 8.08% and the net trimming loss was 3.26% after 90-day storage with partial stack cooling at 2.7oC covered with a 56-hole film. The quality of spring kimchi cabbage after 90-day storage was fresh without physiological disorders.

Experiments were conducted to evaluate the performance factors such as type of working fluid, flow direction, arrangement and stage of loop thermosyphon heat exchanger for ESS battery container cooling. Pentane showed slightly better performance of the heat exchanger than R-134a as a working fluid. Driving the fan in the suction direction showed improved performance compared to the blowing direction. The two-stage heat exchanger increased the heat transfer rate by more than 30% at the same temperature difference compared to the single-stage heat exchanger. Also, the counterflow flow showed better performance than the parallel flow in the two-stage heat exchanger.

This study was conducted to provide a basis for raising farm income by increasing the yield and extending the cultivation period by creating an environment where crops can be cultivated normally during high temperatures in summer. The maximum cooling load of the multi-span greenhouse with a floor area of 504 m2 was found to be 462,609 W, and keeping the greenhouse under 32°C without shading the greenhouse at a high temperature, it was necessary to fog spray 471.6 L of water per hour. The automatic fog cooling control device was developed to effectively control the fog device, the flow fan, and the light blocking device constituting the fog cooling system. The fog cooling system showed that the temperature of the greenhouse could be lowered by 6°C than the outside temperature. The relative humidity of the fog-cooled greenhouse was 40-80% during the day, about 20% higher than that of the control greenhouse, and this increase in relative humidity contributed to the growth of cucumbers. The relative humidity of the fog cooling greenhouse during the day was 40-80%, which was about 20% higher than that of the control greenhouse, and this increase in relative humidity contributed to the growth of cucumbers. The yield of cucumbers in the fog-cooled greenhouse was 1.8 times higher in the single-span greenhouse and two times higher in the multi-span greenhouse compared to the control greenhouse.

The improvement of heat transfer in water cooling passage of lithium-ion battery is numerically studied by employing trapezoidal vortex generators. Battery Design StudioⓇ software is used for modeling electro-chemical heat generation in the battery. The conjugated heat transfer is analyzed with the commercial package STAR-CCM+ in terms of inlet flow velocities. The result shows that vortex generator enhances the convective heat transfer by developing thermal boundary layers and secondary flows in downstream, which results in reducing the average temperature of the battery by about 1℃. The heat transfer is enhanced for the whole inlet velocity, while the pressure loss sharply increases at more than inlet velocity of 0.1m/s. The optimum inlet velocity is around 0.1m/s for in terms of the heat transfer and pressure loss.

The purpose of this study is to analyze the temperature and heat resistance distribution, which is a criterion for evaluating the cooling performance, by using computer simulation of the cooling system combined with the CPU of the individual highest heat generation section, and use it as important data for the heat sink design. Using a single material of Al 6063-T5, which is an integral part of the desktop, fan and heat sink, fins and base, the analysis was carried out with various fin numbers, thicknesses, pitches and shapes of heat sinks. Ambient temperature, 25°C, heat source, 130W and cooling fan speed, 2500 rpm (50CFM) were used as boundary conditions, and heat transfer characteristics regarding temperature distribution and heat resistance were investigated using ANSYS Icepak. As a result, it has been found that as the number of fins of heat sink increases, the heat dissipation area increases to decrease heat resistance, and as the distance between each fin decreases, the ventilation resistance increases to decrease the flow intensity of the cooling air in contact with the heat dissipation area. The sunburst array also exhibits better heat transfer characteristics by obtaining a lower distribution of heat resistance with a cooling effect of about 10°C than the one-way basic array.

판형 열교환기는 1920년대부터 본격적으로 상업화되었으며, 이후 판형 열교환기의 기본 컨셉은 지금까지도 거의 변화가 없었지만 고온, 고압 그리고 대용량 열교환에 적용되기 위해 설계 및 제작 방법들이 혁신적으로 발전하여 지금에 이르게 되었다. 판형 열교환기의 개발 트렌드는 전열 효율이 좋으면서 압 력강하가 낮고 또한 유체 분배가 잘되는 전열판의 개발과 일치한다. 본 연구에서는 이러한 트렌드를 만족 시키는 선박용 중속엔진 오일 냉각용 판형 쿨러 개발과 관련된 주요 과정들을 소개하고, 또한 개발된 판형 오일쿨러의 전열성능을 실험적으로 분석하여 이에 대한 결과를 제공하고자 한다. 본 연구에서 판형 쿨러는 구조적 특징으로 인해 직접 판벽 온도를 측정할 수 없어 수정된 Wilson Plot 방법을 응용하여 열전달계수를 구하였다. 오일-물 실험 전에 물-물 실험을 통해 우선 물측의 열전달계수와 압력강하량을 구하였고, 그 결과를 바탕으로 오일측의 열전달계수를 구하였다. 양측 모두 유량 증가에 따라 열전달 성능은 증가하였지 만, 압력강하량도 동시에 증가하였다. 그리고 실험을 통해 본 연구에서 개발된 판형 오일쿨러가 개발목표치를 성공적으로 달성하였음을 확인할 수 있었다.

Experiments were conducted on the operating characteristics and performance of various types of working fluid, filling amount and heat flow rate of a loop thermosyphon for cooling ESS battery container. As results of performance test on various working fluids, HFE-7100 and R-134a as a working fluids showed unstable operating and low performance due to vapor pressure drop, and performance was improved by increasing the number of vapor lines for reducing a pressure drop. In this study, n-pentane was more stable and showed better thermal performance among various working fluids.

In this study, three kinds of metal chills such as SS400, AC4CH and brass, with different thicknesses of 40 ~ 80 mm, were applied for low pressure casting of Al-Si alloy to control cooling rate. The microstructural characteristics with increasing cooling rate were represented using factors including D1, D2, size of primary α phases and shape factor and size of eutectic Si. The tensile properties were investigated and additionally analyzed based on the microstructural characteristics. As the cooling rate increased, D1, D2, and sizes of primary α phases and eutectic Si apparently decreased and the shape factor of eutectic Si increased to over 0.8. The ultimate tensile strength (UTS) and yield strength (YS) increased with decreasing D1, D2, and size of primary α phases, while elongation increased with decreasing size of eutectic Si and concurrently increasing shape factor of eutectic Si. This indicated that the primary α phases and eutectic Si in Al-Si alloy were refined with increasing cooling rate, resulting in improvement of UTS and YS without sacrificing elongation. After the tensile test, preferential deformation of primary α phases was observed in the Al-Si alloy produced at higher cooling rates of more than 0.1 K/s.

In this study, heat exchangers used in data center and building air-conditioners were tested according to the type of heat exchangers to select them for commercial use. The experiment was performed three samples, one micro channel heat exchanger, the same volume oval coil and the same performance oval coil. The experiment conducted under actual operation conditions in the data center and building. Micro-channel heat exchanger has lower air side pressure drop and higher capacity per volume than oval coil. It may be advantageous when the installation small space or the little design static pressure in the fan, such as in-row systems or CRAC installed in data center.