http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
( Riguang Chi ),정원식 ( Won-sik Chung ),이계복 ( Kye-bock Lee ),이석호 ( Seok-ho Rhi ) 충북대학교 산업과학기술연구소 2017 산업과학기술연구 논문집 Vol.31 No.1
Lithium ion batteries have a thermally dissolved issue in processing to remove heat generated during charging and discharging. Battery life will be degraded with unexpected aging which is can be happened thermally. In order to resolve this performance degradation due to the thermal failure/aging, mainly conventional convective air or liquid cooling methods have been proposed to cool highly generated heat in the battery usage. But these methods have insufficient cooling ability. Also it needs large flow space to pass through cooling medium. Recently, new battery cooling systems as trial methods such as PCM or heat pipe have been proposed and reported their research works. In the present study, non conventional oscillation heat pipe with top heating/bottom cooling mode in terms of heating position comparing to the conventional oscillating heat pipe. Due to the unique structure of electric vehicles, the cooling channel must be installed in the bottom on the vehicle. Also to install large number of battery cells, they should be tightly contacted without any flow area. Therefore the present cooling method can be one of the solutions for future electric vehicles. The cooling performance with correct pressure induced oscillatory behavior was tried to investigated to find the optimum dimensional design. The design goal of the current cooling system with 10 W/cell can be obtained experimentally and numerically.
( Riguang Chi ),정원식 ( Won-sik Chung ),이계복 ( Kye-bock Lee ),이석호 ( Seok-ho Rhi ) 충북대학교 산업과학기술연구소 2017 산업과학기술연구 논문집 Vol.31 No.1
The oscillating characteristics of slug vapor or plug liquid flow in a capillary tube called as oscillating heat pipe(OHP) is presented. The oscillation phenomena in a capillary tube including effects of capillary force, dimensions, gravitational force, and initial pressure distribution etc. of the working fluid were observed and this working conditions were considered to find the optimum design condition. While it demonstrates that the capillary tube diameter, heating-cooling length, slug bubble size, and unit cell numbers affect the heat transfer and oscillation performance, Also these various working parameters of the OHP significantly affect the frequency and amplitude of oscillating motion in the capillary tube. An experimental study of a closed loop oscillating heat pipe was conducted. The oscillating heat pipes charged with distilled water was tested. In a vertically oriented top heating mode, the oscillating phenomena of the slug flow in the oscillating heat pipe was observed. This paper attempts to investigate the thermal operation behavior of OHP in terms of oscillating behavior. In the present study, the working condition of OHP with the non-conventional heating/cooling mode was verified experimentally. Meanwhile, some promising and innovatory applications of the OHP are also proposed for future electric vehicles. This paper is expected which can provide the basic operation principle of OHP with uneven working condition.
( Riguang Chi ),송의혁 ( Eui-hyeok Song ),최재혁 ( Jae-hyuck Choi ),이동훈 ( Dong-hun Lee ),이석호 ( Seok-ho Rhi ) 충북대학교 산업과학기술연구소 2019 산업과학기술연구 논문집 Vol.33 No.2
Recently, producing electric power with PEMFC (Proton-exchange membrane fuel cell) is one of the solution to overcome environmental and energy crisis. Resulting products of PEMFC are electric power, water and heat by the electrochemical reaction of hydrogen and oxygen. So in the fuel cell system, not only do you supply the reactants to the stack, but you also have to take good care of the water and heat that is the byproduct of the reaction. PEMFC produces a similar amount of waste heat to its electricity output. Thermal management of PEMFC is critical aspect to optimize the performance and durability of PEMFCs. Small temperature deviation of PEMFC can lead deterioration of the performance and operation stability. Accordingly, the current simulated design trial is focused on its operation safety. And characteristic analysis of heat exchangers applied for PEMFC was performed. Simulated results show that the cooling water should be kept under 45~50℃.
김범진 ( Bum-jin Kim ),( Riguang Chi ),이석호 ( Seok-ho Rhi ) 충북대학교 산업과학기술연구소 2018 산업과학기술연구 논문집 Vol.32 No.2
Recently, electric vehicles (EV) drived by Li-ion battery are one of the solution to overcome environmental and energy crisis. Due to high energy density, lithium-ion batteries are widely used in electric vehicles. However, thermal management of batteries in EV is very important issue due to poor heat resistance of lithium ions. Temperature and heat generation outside the optimal operation range can have a severe influence on the reliability and lifetime of Li-ion battery cells. Therefore, it is preliminary investigation for the research of vehicle battery systems to study thermal characteristics of a single or multi cells. The performance and lifetime of lithium ion (Li-ion) batteries are strongly affected by the internal operating temperature. Thermal characterization of battery cells is very important to keep consistent operation of Li-ion battery applications. Therefore, the main focus of the present work is to characterize the thermal behavior of Li-ion battery cell by simulatory study. The specific heat generation of cell was quantified at the natural convective cooling environment. In addition, the heat generation and temperature profile of a cell were simulated for different discharging rates from 1C to 5C-rates. Internal peak temperature of the Li-ion cell was investigated during different C-rates. In 5C operation, 27.81 W was generated inn a cell and 327.32K was observed on the surface.
채희일 ( Heui-il Chae ),( Riguang Chi ),이석호 ( Seok-ho Rhi ) 충북대학교 산업과학기술연구소 2019 산업과학기술연구 논문집 Vol.33 No.2
Recently, optimum fin design involved with its geometries is important to improve the heat transfer performance without increasing fin number. When the junction temperature of a semiconductor reach over its maximum allowable design limit, the device will be broken down. One of the common and conventional method to remove the generated heat is using a finned heat sink with high thermal conductive material. And it is directly contacted to the heat source surface of the electronic component. Heat sink usually consists of a flat base with lots of fin arrays to increase the heat transfer area. The greater the surface area, the better it is able to dissipate the heat generated. The most usual cooling methods could be natural or forced convection with typical fluid cooling mediums. In the present study, the non-uniform geometrical pin-fin arrays are studied in terms of effects of fluid flow, different fin geometries, and so on. Three different fin geometries were used to study and compared to each other to determine the most efficient heat transfer performance. The goal of study is to optimize heat transfer performance of the heat sinks studied in a range of configuration based on fin geometries. The simulation shows slight variation with different geometries. The flow direction to the highest fin is allowable to get higher heat transfer performance.
송의혁 ( Eui-hyeok Song ),( Riguang Chi ),유대겸 ( Dae-gyeom Yu ),이석호 ( Seok-ho Rhi ),이동주 ( Dong-ju Lee ),이계복 ( Kye-bock Lee ) 충북대학교 산업과학기술연구소 2019 산업과학기술연구 논문집 Vol.33 No.1
Power electronics devices are now widely used to efficiently deliver electrical power in hybrid/electric cars, home electronics, telecommunication, and so on. Large heat accompanied with these power electronics should be transmitted to the heat sink. In the present study, cooling technologies based on heat sink with different material and thermal properties. High cooling performance can manage junction temperatures to achieve goals for system efficiency, product cost, and system reliability. Cooling technologies depend on heat spreading and moving by heat conduction associated with convection. Usually, natural or forced air cooling heat sink provides efficient heat spreading. Thermal stress of electronics PCB is affected by thermal expansion in interconnection with different material. In the present study, pin fin heat sinks of different materials were investigated in terms of 3 dimensional thermal conductivity allocation. In this analysis, the cooling performance was observed in three terms of chip junction temperature variation. heat sinks made of usual metallic materials such as Copper and Aluminum were compared with heat sinks of orthographic thermal conductivity composite materials. The pin-fin heat sink of k<sub>x</sub>-k<sub>y</sub>-k<sub>z</sub> = 810-52-810 W/m-K composite material shows slightly higher thermal performance. The optimum heat sink design should be accompanied with special care on thermal conductivity allocation in three dimensional directions.