• 한국정밀공학회지
• /
• 제25권7호
• /
• pp.116-123
• /
• 2008

In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture or causes the stress corrosion cracking and fatigue fracture. Especially, the accidents due to the residual stress occurred at the weld parts of high-temperature and high-pressure pipes and steam headers. Also, the residual stress of the welded part in the recently constructed power plants has been brought into relief as the cause of various accidents. The aim of this study is the measurement of the residual stress using the x-ray diffraction method. The merits of this are more accurate and applicable than other methods. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The variables of tests are the post-weld heat treatment, the surface roughness and the depth from the original surface. The test results were analyzed by the distributed characteristics of the full width at half maximum intensity (FWHM) in x-ray diffraction intensity curve and by the relation of hardness with FWHM.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
• /
• pp.329-332
• /
• 1999

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as underground box structure, mat-slab of nuclear reactor buildings, dams or large footings, foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, pre-cooling which lowers the initial temperature of fresh concrete with ice flake, pipe cooling which cools the temperature of concrete with flowing water, design change which considers steel bar reinforcement, operation control and so on. The objective of this paper is largely two folded. Firstly we introduce the cracks control technique by employing low-heat cement mix and thermal stress analysis. Secondly it show the application condition of the cracks control technique like sidewall of LNG in Inchonl.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
• /
• pp.293-298
• /
• 1999

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as underground box structure, mat-slab of nuclear reactor buildings, dams or large footings, foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, pre-cooling which lowers the initial temperature of fresh concrete with ice flake, pipe cooling which cools the temperature of concrete with flowing water, design change which considers steel bar reinforcement, operation control and so on. The objective of this paper is largely two folded. Firstly we introduce the cracks control technique by employing low-heat cement mix and thermal stress analysis. Secondly it show the application condition of the cracks control technique like the subway structure in Seoul.

• 한국생산제조학회지
• /
• 제22권5호
• /
• pp.789-794
• /
• 2013

In this study, the temperature, heat emission per unit time, and thermal stress or deformation of a radiator fan made of polyethylene or aluminum are analyzed for investigating its strength durability. Heat transfer in the case of the aluminum radiator fan is better than that in the case of the polyethylene radiator fan. Further, heat emission in the case of the aluminum fan is poorer than that in the case of the polyethylene fan. Moreover, because the thermal deformation of aluminum is much smaller than that of polyethylene, the thermal durability of the aluminum fan is better than that of the polyethylene fan. In an open space in front of the radiator and the closed space of the engine behind it, the thermal cooling effect of the polyethylene fan is better than that of the aluminum fan. Further, since polyethylene is lighter in weight than aluminum, polyethylene, as a nonmetallic plastic, is more suitable as a material of an automotive radiator. However, because of the higher strength durability of the aluminum fan, it is better than the polyethylene fan under high-temperature conditions or in the case of a complex pipe.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
• /
• pp.249-256
• /
• 2009

The cooling technology of power conversion semiconductors in the propulsion system for the HEMU(High Electrical Multi Unit) are applied in water cooling method and phase change method such as the immersed type and the heat pipe type. This research designs and manufactures the water cooling system that could cool about heat load Q=2kW and performance tests to apply it by an electric power conversion semiconductors(IGBT) cooling technology. Experimental condition made change of a flow rate, an air velocity and a heat load to confirm operation characteristics of water cooling device, and when is heat load 2kW, air velocity 20 m/s, and water flow rate 7kg/s, it is about $80^{\circ}C$ to temperature of cooling plate.

• 전자통신동향분석
• /
• 제38권6호
• /
• pp.41-51
• /
• 2023

Heat dissipation technology for semiconductors and electronic packaging has a substantial impact on performance and lifespan, but efficient heat dissipation is currently facing limited improvement. Owing to the high integration density in electronic packaging, heat dissipation components must become thinner and increase their performance. Therefore, heat dissipation materials are being devised considering conductive heat transfer, carbon-based directional thermal conductivity improvements, functional heat dissipation composite materials with added fillers, and liquid-metal thermal interface materials. Additionally, in heat dissipation structure design, 3D printing-based complex heat dissipation fins, packages that expand the heat dissipation area, chip embedded structures that minimize contact thermal resistance, differential scanning calorimetry structures, and through-silicon-via technologies and their replacement technologies are being actively developed. Regarding dry cooling using single-phase and phase-change heat transfer, technologies for improving the vapor chamber performance and structural diversification are being investigated along with the miniaturization of heat pipes and high-performance capillary wicks. Meanwhile, in wet cooling with high heat flux, technologies for designing and manufacturing miniaturized flow paths, heat dissipating materials within flow paths, increasing heat dissipation area, and reducing pressure drops are being developed. We also analyze the development of direct cooling and immersion cooling technologies, which are gradually expanding to achieve near-junction cooling.

• 전력전자학회논문지
• /
• 제4권3호
• /
• pp.257-267
• /
• 1999

본 논문은 대용량 컨버터의 수냉식 방열 시스템에 관한 내용을 담고 있다. 본 논문은 수냉식 방열 시스템의 이론적 근거와 모델링을 제시하고 전력용 반도체(싸이리스터)의 열량 계산을 수학적인 모델링에 근거하여 제시하였으며 실제로 우리나라에 설치되어 있는 제주-해남 HVDC 시스템에 적용하여 타당성을 검증하였다.

• 한국수소및신에너지학회논문집
• /
• 제31권2호
• /
• pp.169-176
• /
• 2020

There is a growing interest in hydrogen energy utilization since an alternative energy development has been demanded due to the depletion of fossil fuels. Hydrogen is produced by the reforming reaction of natural gas and biogas, and the electrolysis of water. An solid oxide electrolyte cell (SOEC) is reversible system that generates hydrogen by electrolyzing the superheated steam or producing the electricity from a fuel cell by hydrogen. If the water can be converted into steam by waste heat from other processes it is more efficient for high-temperature electrolysis to convert steam directly. The reasons are based upon the more favorable thermodynamic and electrochemical kinetic conditions for the reaction. In the present study, steam at over 180℃ and 3.4 bars generated from a boiler were converted into superheated steam at over 700℃ and 3 bars using a cylindrical steam superheater as well as the waste heat of the exhaust gas at 900℃ from a solid refuse fuel combustor. Superheated steam at over 700℃ was then supplied to a high-temperature SOEC to increase the hydrogen production efficiency of water electrolysis. Computational fluid dynamics (CFD) analysis was conducted on the effects of the number of 90° elbow connector for piping, insulation types and insulation layers of pipe on the exit temperature using a commercial Fluent simulator. For two pre-heater injection method of steam inlet and ceramic wool insulation of 100 mm thickness, the highest inlet temperature of SOEC was 744℃ at 5.9 bar.

• Journal of Biosystems Engineering
• /
• 제36권5호
• /
• pp.319-325
• /
• 2011

This study was conducted to figure out the diagnosis basis of cooling performance depending on water amount in the refrigerant of air conditioner, which can be estimated by the temperatures and pressures along the refrigerant circulation line. A car air conditioner of SONATA III (Hyundai motor Co., Korea) was tested at maximum cooling condition at the engine speed of 1500 rpm in the room controlled at 33~$35^{\circ}C$ air temperature and 55~57% relative humidity conditionally. Measured variables were temperature differences between inlet and outlet pipe surfaces of the compressor, condenser, receive drier and evaporator; and high pressure and low pressure in the refrigerant circulation line; and temperature difference between inlet and outlet air of the cooling vent of evaporator. In this study, changes of the water amount in the refrigerant were correlated to the temperatures and pressure changes and also water amount caused poor cooling performance. As water amount increased in the refrigerant in the air conditioner, the performance of the cooling or the heat transfer became worse. Temporal variations of the surface temperature of the evaporator outlet pipe and the low-side pressure showed various patterns that could estimate the water amount. When the water amount caused bad cooling performance, the patterns of the temperature of the evaporator outlet pipe indicated irregular fluctuation greater than $5^{\circ}C$. When the diagnosis system is using just external sensors of the low-side pressure and the temperatures of inlet and outlet air of cooling vent of the evaporator, the precise pattern of bad cooling performance caused by excess water amount in the cooling line was irregular pressure fluctuation, 25 kPa under 120 kPa, and temperature, $12^{\circ}C$ and less.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2004년도 하계학술발표 논문집
• /
• pp.159-159
• /
• 2004