• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.990-995
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• 2009

Experimental basic study was performed to understand the characteristics of sub-cooled refrigerant using a cold heat storage system. This system was made up general vapor-compression refrigeration cycle added sub-cooler and ice storage tank. The purpose of this study are to application use of cold-heat storage systems multiplicity of fields and to understand of sub-cooling system. At the condition using ice storage system, the ice making process was operated during night time by electric power. And then, the refrigerant was sub-cooled using stored cold-heat after being discharged from the air cooling condenser during the day time. Comparing the result at general operation with the operation using sub-cooling system. This study showed the effects of the sub-cooled degree. The cooling performance was increased owing to the sub-cooling of refrigerant during day time, and the compressor consume power was a little decreased. Thus the COP was also increased owing to the sub-cooling of refrigerant.

• 한국대기환경학회지
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• 제24권1호
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• pp.83-90
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• 2008

In order to clarify the urbanization intensity of Daegu Metropolitan and its characteristics, comparative study on the variation of the cooling rate of two different sites was carried out using observation data for 40 years by Korea Meteorological Adminstration. Daegu Metropolitan and Chupungnyung represent well urbanized and rural areas, respectively. In comparison with Chupungnyung, yearly mean temperature at Daegu Metropolitan increases rapidly and especially the differences of minimum temperature increasing rate during 40 years becomes greater. These differences of regional warming are caused by the different urbanization intensity between two sites. And the impact of anthropogenic heat due to urbanization should be stronger in nighttime than in daytime. Sensible heat advection by regional wind during 6 hours from 18 LST contributes to atmospheric cooling. For this reason wind speed is in proportion to cooling rate of atmosphere. However, wind after 24 LST induces the warm air advection and makes decrease the cooling rate in urban area. Although the cooling rates between Daegu Metropolitan and Chupungnyung are some different, the variation tendencies of cooling rate of two site are almost same. Therefore atmospheric cooling rate in nighttime tends to be associated with the intensity of wind speed.

• 한국주조공학회지
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• 제35권2호
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• pp.23-28
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• 2015

This work presents the effect of the cooling rate on the precipitation of super duplex stainless steel. Specimens of super duplex stainless steel with a specific composition were cooled at various cooling rates after being melted at $1550^{\circ}C$ in a directional solidification furnace. Ferrite (${\delta}$), Austenite (${\gamma}$), Sigma (${\sigma}$), and Chi (${\chi}$) phases were precipitated when the cooling rate was lower than 0.22 K/s. When the cooling rate was 0.22 K/s or faster, ${\sigma}$ and ${\chi}$ phases were not precipitated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.44-46
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• 2003

Nowaday it is trend to be one cooling radiator and cooling fan from separate engine radiator and air condition radiator in cars. For the cooling fan is developed a electrical motor which is limited in size. The motor should be working in silence and have no electromagnetic Problem and high efficiency. In this paper will be proposed some parameters for improvement of the efficiency of a BLDC motor which is developed for the cooling system after theoretical and experimental investigation.

• Corrosion Science and Technology
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• 제4권1호
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• pp.23-28
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• 2005

Several plasma-sprayed ceramic coatings with two- and three-layers were characterized and tested for the application of cooling tube coatings of oxygen convert gas recovery system (OG cooling system) in the steel making plant. Thermal cycling tests using a torch heating with compressed air cooling were carried out and characterized before and after the tests. The effects of metallic bond coat as well as ceramic top coat were also studied. Possible failure mechanisms with low carbon steel substrate were assessed in term of microstructure, porosity, bond strength, thermal expansion coefficient, and the phase transformation. Finally, the results of field tests at the OG cooling system are presented and discussed their microstructural degradation. Test results have shown that three-layered coatings perform better than two-layered coatings.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.171-175
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• 2003

The sub-cooled nitrogen cooling system at 65 K with GM cryo-cooler is developed for cooling down the DC reactor of 6.6 ㎸-200 A class HTS Fault Current Limiter(SFCL). The sub-cooled nitrogen cooling is more economic than saturated nitrogen cooling, because the length of HTS wire is reduced in the same capacity, as well as, more stable. The cooling system with the GM cryo-cooler installed on the cryostat is not only compact but also efficient for energy saving. In the nitrogen vessel, after evacuating with vacuum pump to saturated nitrogen at 65 K, sub-cooled nitrogen at 65 K is made by putting in gas helium to 1 atm. During the short circuit test occurring the fault current of 1000 A, the sub-cooled nitrogen cooled DC reactor for SFCL is kept the state of sub-cooled nitrogen at 65 K.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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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.

• 한국정밀공학회지
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• 제15권9호
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• pp.25-32
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• 1998

The forced cooling system is designed to shorten the overhaul time of steam turbine, which is important in view of economic concern of utility companies, Forced cooling of the hot turbine is achieved by suction of air flow into the turbine after the turbine shuts down. The heat transfer process by suction of air flow can cause thermal stress due to the thermal gradients. In this paper, the analysis of heat transfer is performed to calculate the air flow rate. Based on the prediction of cyclic fatigue damage and the experience, the cooling equipment is designed for shortening the cooling time of steam turbine.

• 한국주조공학회지
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• 제41권4호
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• pp.349-356
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• 2021

우수한 기계적 성질과 가격경쟁력을 갖는 구상흑연주철 합금 개발을 위해 Cu와 Sn을 소량 첨가한 고 Mn 구상흑연주철의 응고 후 냉각조건에 따른 미세조직과 기계적 특성을 분석하였다. 첨가원소인 Cu와 Sn의 경우 펄라이트 형성 촉진을 통한 인장특성 향상을 위해 선택하였다. 또한 물성에 미치는 냉각속도의 영향을 확인하기 위해, Mg 처리된 다양한 조성의 합금을 블록시편에 주입한 후 주형 내 냉각과 800℃에서 주형 해체 후 공랭의 두 가지 냉각 조건을 비교분석하였다. 주형 내 냉각 시편의 경우, 펄라이트 분율은 27-44%, 인장강도와 연신율은 각각 513-568N/mm²와 10.4-14.3%로 나타났다. 반면, 이른 형해체 공랭 시편의 경우에는 펄라이트 분율은 77~85%, 인장강도와 연신율은 각각 728~758N/mm²와 3.2~6.0% 이었다. 결론적으로, 소량의 Cu 및 Sn 함유 Mn 구상흑연주철의 공랭 시 괄목할만한 인장강도와 연신율의 증가를 확인할 수 있었다.

• Nuclear Engineering and Technology
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• 제49권5호
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• pp.979-988
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• 2017

The feasibility of cooling in a pressurized heavy water reactor after a large break loss-of-coolant accident has been analyzed using Multidimensional Analysis of Reactor Safety-KINS Standard code during the recirculation phase. Through evaluation of sensitivity of the fuel channel temperature to various effective recirculation flow areas, it is determined that proper cooling of the fuel channels in the broken loop is feasible if the effective flow area remains above approximately 70% of the nominal flow area. When the flow area is reduced by more than approximately 25% of the nominal value, however, incipience of boiling is expected, after which the thermal integrity of the fuel channel can be threatened. In addition, if a dramatic reduction of the recirculation flow occurs, excursions and frequent fluctuations of temperature in the fuel channels are likely to be unavoidable, and thus damage to the fuel channels would be anticipated. To resolve this, emergency coolant supply through the newly installed external injection path can be used as one alternative means of cooling, enabling fuel channel integrity to be maintained and permanently preventing severe accident conditions. Thus, the external injection flow required to guarantee fuel channel coolability has been estimated.