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최순호(Soon-Ho Choi),김창복(Chang-Fu Jin),최현규(Hyun-Kue Choi),윤석훈(Seok-Hoon Yun),김명환(Myoung-Hwan Kim),오철(Cheol Oh) 한국마린엔지니어링학회 2005 한국마린엔지니어링학회 학술대회 논문집 Vol.2005 No.-
Although the law of classical fourier heat conduction predicts the heat conduction phenomena occurred in most engineering fields with a good accuracy, it is also well-known that the conventional fourier law of a heat conduction has an application limit when the heating and cooling are periodic for a short duration or when the heat conduction is analyzed in the extremely low temperature region. This application limit of classical fourier law results from the fact that it assumed the infinite speed of a heat wave. In this study, we investigated the feasibility of whether the molecular dynamics could be used to calculate the speed of a heat wave through a solid. The calculated sound velocity showed a good agrement with the theoretical prediction qualitatively. From the calculated results, we confirmed that the same methodology can be applied the evaluation of the speed of a heat wave.
문수범(Soo Beom Moon),최현규(Hyun Kue Choi),최순열(Soon Yeol Choe),김창복(Chang fu Jin),김경근(Kyung Kun Kim),최순호(Soon-Ho Choi) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
An ejector driven by a liquid is a fluid transfer equipment to be used for mixing, for maintaining vacuum, and for overcoming a poor suction condition. At present, most ejectors have been made from the casting process, which is time and cost consuming process. Therefore, a new production method is desired to produce a ejector massively. In this experimental study, we proposed a new type ejector produced from the commercial fitting materials and the welding process with an orifice type motive nozzle. The proposed ejector has a good integrity compared with the conventional ejector because the forging materials of the fittings has more strength than the casting materials. Furthermore, we adopted a multi-opening orifice type nozzle for improving a suction capacity and compared with a single-opening orifice type nozzle. From the experiments, we confirmed that the multi-nozzle had a good suction capacity than the single nozzle and the proposed new type ejector showed higher vacuum than the conventional type ejector in non-load condition. These improved characteristics of a new type one suggests a new manufacturing method to produce an ejector by using the commercial fittings. Therefore, the proposed ejector in this study can considerably reduce the manufacturing time and cost while its performance is largely increased.
최현규(Hyun-Kue Choi),최순호(Soon-Ho Choi),최순열(Soon Youl Choe),김창복(Chang fu Kim),김경근(Kyung Kun Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
A state of equilibrium means that the thermophysical properties must be equal no matter where a measurement is performed in a system. However, some recent studies reported that there exists the temperature difference over a liquid-vapor interface even though the system is at a state of equilibrium when a system reduces to a nanoscalesize. Those conclusions leave a strong question as to whether the definition of a thermal equilibrium state should be changed in the case of nanoscale systems. In the present study, we carefully investigated the temperature profile over a liquid-vapor interface using the molecular dynamics (MD) simulation and found that the temperature difference between a liquid phase and a vapor phase over an interface resulted from the methodological difference of the temperature calculation. That is, the definition of a thermal equilibrium state has no reason to be changed no matter how a system would be small.