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이희준(H. LEE),강종민(J. KANG),박승철(S. PARK),박해성(H. PARK),이경준(K. LEE),이규동(K. LEE),조수희(S. CHO) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.6_2
The regulation of the pass-by-noise has become severe in 1996. In order to reduce the pass-by-noise, noise sources ,have to be identified at first. Lead wrapping method is used for source ranking test. It was found that major sources are the engine and the exhaust system in the commercial vehicle, Samsung 15t dump truck.<br/> The pass-by-noise level is then reduced by the modifications of engine enclosure and the redesign of exhast system.<br/>
이희준(H.J. Lee) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.2
A numerical study of subcooled onset of nucleate boiling (ONS) in a micro-channel under pulsed heating using volume of fluids (VOF) model was conducted. The VOF simulation adopting the existing experimental condition is compared to the experimental data. The time to ONS was determined when the void Faction at the microheater surface first appeared. The theoretical superheat for homogeneous nucleation relatively predicts the transient ONB results of convective flow of water well based on local temperature distribution. It was found that once heat load increases at the heater, transient flow boiling starts to occur faster.
이희준(H. J. Lee),한상엽(S. Y. Han),정용갑(Y. G. Chung),조남경(N. K. Cho),길경섭(G. S. Kil),김영목(Y. K. Kim) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.3
A heated and expanded helium is used to pressurize liquid propellants in propellant tanks of propulsion system of liquid propellant launch vehicles. To produce a heated and expanded helium, an hot-gas heat exchanger is used by utilizing heat source from an exhausted gas, which was generated in a gas generator to operate turbine of turbo-pump and dumped out through an exhaust duct of engine. Both experimental and numerical approaches of hot-gas heat exchanger design were conducted in the present study. Experimentally, siliconites - electrical resistance types - were used to simulate the full heat condition instead of an exhausted gas. Cryogenic heat exchangers, which were immersed in a liquid nitrogen pool, were used to feed cryogenic gaseous helium in a hot-gas heat exchanger. Numerical simulation was made using commercially utilized solver - Fluent V.6.0 - to validate experimental results. Helically coiled stainless steel pipe and stainless steel exhausted duct were consisted of tetrahedron unstructured mesh. Helium was a working fluid inside helical heat coil and regarded as an ideal gas. Realizable k-ε turbulent modeling was adopted to take turbulent mixing effects in consideration. Comparisons between experimental results and numerical solutions are presented. It is observed that a resulted hot-gas heat exchanger design is reliable based on the comparison of both results.
마이크로채널 기판에서 비정상 복합 열전달의 수치적 연구
이희준(H. J. Lee) 한국전산유체공학회 2012 한국전산유체공학회지 Vol.17 No.4
A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under pulsed heating was conducted. It was found that the time constant is not affected by the pulse heating magnitude at same operating condition. Furthermore, the time constant increases with low substrate thermal diffusivity, low Reynolds number, and large channel diameter. Since the time constant is a dominant parameter to characterize transient heat transfer, it should be considered for transient convective heat transfer coefficient.