• Horticultural Science & Technology
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• v.33 no.2
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• pp.233-241
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• 2015

Kimchi cabbage 'Choon Gwang' cultivar that was grown in highlands in Gangneung was subjected to predrying, room cooling, and forced air cooling, and then packed with/without 0.02 mm HDPE film to investigate the effect of postharvest treatment on quality characteristics during 8 weeks storage at $2^{\circ}C$ (RH $90{\pm}5%$). Weight loss in forced air cooling and room cooling was lower than 3-4% with 0.02 mm HDPE film liner treatment during storage. However, it was only below 10% in room cooling without liner treatment and forced air cooling without liner treatment led to the highest weight loss, above 15%. Conversely, the control had lower weight loss than the others. SSC was $2-4^{\circ}brix$ for all treatments and there was no difference between postharvest treatments and liner treatments. Color index and firmness both showed no differences with/without 0.02 mm HDPE film and postharvest treatments. In sensory evaluation, forced air cooling with liner treatment was effective, with the highest score, especially in appearance and crispness. After 6 weeks, control kimchi cabbage without liner treatment was damaged seriously in appearance and the internal color had changed to brown. Room cooling and predrying with liner treatment changed the start of internal browning to after 8 weeks storage.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.922-927
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• 1998

Pipe cooling has been popularly used in the mass concreting work to reduce temperature of the structure since it is known to be the easiest way to apply and has been the customary usage. But wrong application of the system results in the harmful effect on the structure by crack formation due to thermal shocks and improper cooling schemes. Thus, this study aims at the suppling of effective cooling methods through parametric study. For this, circulating method, velocity of water supply and circulating duration were selected as critical factors affecting the effectiveness of cooling system. As a results of thermal analysis, it was found that too much thermal gradient in the vicinity of the pipe creates localized radial or circumferential cracks. The duration of circulating cooling may be recommended to be as short as several days which may safely reduce the concrete temperature to below a final stable value. It was also found that pipe cooling is more effective to decrease the degree external restraints than internal one.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.9
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• pp.952-960
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• 2008

Fan noise prediction method is presented for air conditioning, automobile and electronic cooling system applications where fan acts as an internal equipment having very complicated flow interaction with other various system components. The internal flow paths and distribution in the fan-applied systems such as computer or air conditioner are analyzed by using the FNM(flow network modeling). Fan noise prediction method comprises two models for the discrete frequency noise due to rotating steady aerodynamic lift and blade interaction and for the broadband noise due to turbulent boundary layer and wake vortex shedding. Based on the fan operation point predicted from the FNM analysis results and fan design parameters, the present far noise model predicts overall sound pressure level and spectrum. The predictions for the flow distribution, the fan operation and the noise level in air cooling system by the present method are well agreed with 3-D CFD and actual noise test results.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.297-302
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• 2000

Pipe cooling method is widely used for reduction of hydration heat and control of cracking in mass concrete structures. However, in order to effectively apply pipe cooling systems to concrete structure, the coefficient of flow convection relating the thermal transfer between inner stream of pipe and concrete must be estimated. In this study, a device measuring the coefficient of flow convection is developed. Since a variation of thermal distribution caused by pipe cooling has a direct effect in internal forced flows, the developed testing device is based on the internal forced flow concept. Influencing factors on the coefficient of flow convection are mainly flow velocity, pipe diameter and thickness, and pipe material. finally a prediction model of the coefficient of flow convection is proposed using experimental results from the developed device. According to the proposed prediction model, the coefficient of flow convection increases with increase in flow velocity and decreases with increase in pipe diameter and thickness. Also, the coefficient of flow convection is largely affected by the type of pipe materials.

• Transactions of Materials Processing
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• v.5 no.1
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• pp.18-26
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• 1996

In order to investigate the effect of pre-cooling of ingot on void closure in hot plate forging the internal strain and stress distributions are examined quantitatively by using ABAQUS. Simula-tions are carried out on a large slab ingot having the same temperature and the temperature gradient induced by air-cooling. It is shown that pre-cooling produces little effect on the strain behavior but remarkable effect on the hydrostatic stress at the central zone of ingot. The main factors for crushing micro-voids are the effective strain and the time integral of hydrostatic stress in the region surrounding the voids. Based on regression analysis it was found that the distortion of void can be expressed as a polynomial function of the two factors.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.6
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• pp.526-533
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• 2009

In this paper, cycle performance analysis of $CO_2-C_3H_8$ (R744-R290) cascade refrigeration system with internal heat exchanger 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 gas cooling pressure and evaporating temperature in the propane (R290) low temperature cycle and the carbon dioxide (R744) high temperature cycle. The main results were summarized as follows : The COP of cascade refrigeration system of $CO_2-C_3H_8$ (R744-R290) increases with the increasing subcooling degree, but decreases with the increasing superheating degree. The COP of cascade refrigeration system increases with the increasing evaporating temperature, but decreases with the increasing gas cooling pressure. Therefore, superheating and subcooling degree, compressor efficiency, evaporating temperature and gas cooling pressure of $CO_2-C_3H_8$ (R744-R290) cascade refrigeration system have an effect on the COP of this system.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.34.1-34.1
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• 2005

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.314-319
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• 2011

Energy Cost has been rapidly increased with the internal heat gain of data center to keep the temperature condition. But the cooling units for server systems are fully operated to satisfy the indoor temperature condition, it results in the excessive energy consumption. In this study, various cooling systems were studied for data center and cold aisle containment system was proved to be the best solution for server cooling system. Because it protects the cooling zone from the hot aisle space. Effective cooling and prohibition of recirculation air from hot aisle was possible by the cold aisle containment system.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3001-3006
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• 2008

Recently, the internal combustion engines have focused on reducing both the CO2 emissions in order to cope with severe regulations for greenhouse effect. Therefore, various new technologies have been developed in many countries. Among them, the cooling system is spotlighted because it has great effect on fuel efficiency. However, the present engine cooling system is almost same as one of the 50 years ago. The needs for high performance and compact size make it important to improve engine cooling system, down-sizing and control method of coolant flow. Thus, low fuel consumption technology such as control and synthetic management of cooling system was necessary to satisfy with these needs. In this study, we applied electric thermostat to improve the fuel economy. The fuel consumption was compared after driving FTP-75 mode on both conditions which were with a conventional wax thermostat and with a electric thermostat. The coolant temperature of opening the electric thermostat is higher.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.14-19
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• 2014

This study conducts shape optimization of rib turbulator on the internal cooling passage that has triangular cross-section of high pressure turbine nozzle. During optimization, various types of rib turbulator including angled, V-shaped, A-shaped and angled rib with intersecting rib are considered. Each type of rib turbulator is parameterized with attack angle(s), rib height, spacing ratio and bending/intersecting location. For optimization, Design of Experiment (DOE) and Kriging surrogate model are used to utilize computational resource more efficiently and Genetic Algorithm (GA) is used to search the optimum points. As a result, Pareto front of each type of rib turbulator with friction factor that relates to pressure drop in cooling passage and spatially averaged Nusselt number that relates to heat transfer on the wall is drawn and optimum points on the Pareto front are suggested.