• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.8-17
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• 2006

When a flame is stabilized in a tube of a finite thickness, a conductive heat transfer through the tube significantly changes the wall temperature and affects the flame characteristics. Thus the tube length and thermal boundary conditions affect on the structure of the flame in a conductive tube. A one-dimensional analytical study was conducted by employing two energy equations for tubes and mixtures and a species equation for the mixture. Variation of the maximum temperatures and indicating displacements were observed. A parametric study on the effects of inner Peclet numbers, normalized wall conductivities, and heat transfer conditions of the tube was conducted. This study provides essential data for a more efficient computational simulation of the flame stabilized in conductive tubes.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.339-340
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• 1996

In the present study we examine physical characteristics of a thin and rigid magnetic flux tube with a steady flow inside, which is embedded vertically upward in the solar atmosphere. We found from this study that (1) The downward material flow gives rise to a dominant heating in the flux tube which works with the conductive heating in the same direction. However, the upflow flow creates a dominant cooling which works against the conductive heating, resulting in a steeper temperature gradient with a shallower transition region. (2) Since the thickness of the transition region determines the material content in the transition region, a broader transition region of the downflow tube produces a larger differential measure.

• Solar Energy
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• v.20 no.4
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• pp.61-67
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• 2000

The purpose of this study is to improve heat transfer by attaching rectangular fins to tube. Experiments were carried out under the following conditions - Aspect ratio$(W_f/R_f)$ is 0.7, 1.2 and 1.8. Temperature conversion between high and low positions of water in the thermal storage appeared because maximum density point of water is about $4^{\circ}C$ and inlet direction of working fluid influenced conductive heat transfer Compared with the unfinned tube(bare tube), the rectangular tube increased the ice thermal storage energy and the ice thermal storage energy was increased as aspect ratio was increased.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.407-416
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• 2005

The kimchi refrigerator is the electric home appliance which is used for the maturing and preserving of the kimchi in domestic and foreign market. The kimchi refrigerator is composed in 3 main parts as insulation. kimchi container, machinery room. The heat exchanger of kimchi refrigerator is made of aluminum and the other parts are made of steel and polymer. Also, kimchi refrigerator is expensive and heavy as compared with same class of refrigerator until now. In the present study, the possibility to replace heat exchanger from aluminum to thermal conductive plastic was analyzed and experimented. The thermal conductive plastic has $10{\sim}100$ times heat conductivity than that of normal plastic. It is known that heat transfer process is dependent not only conduction but convection or radiation. Thermal conductivity of the applied material in this research is over than 2 W/mK, thermal conductivity doesn't play a vital role on heat transfer. In this study, temperature is the most important parameter on the kimchi refrigerator and the temperature of kimchi refrigerator's heat exchanger was measured and compared with the temperature calibrated by CFD analysis on the inside wall of the kimchi refrigerator. It is important to keep constantly the inside temperature of the Kimchi refrigerator. Besides numerical analyses for the new thermal conductive plastic for heat exchanger were executed with the various height of evaporation tube. A series of experiments were conducted to compare the performance of the two heat exchanger made of aluminum and thermal conductive plastic at the same condition and certified the possibility of the thermal conductive plastic. According to these results, it was confirmed that the conventional aluminium heat exchanger can be replaced by thermal conductive plastic successfully.

• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.24-28
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• 2008

Eddy current are induced when a nonmagnetic, conductive material is moving as the result of being subjected to the magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and conductor. Using this concept, eddy current damping can be used as a form of viscous damping. This paper investigated analytically and experimentally the characteristics of an eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of the eddy current damping is developed from electromagnetics and is verified from Maxwell program and experiments. From these comparisons, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies. In order to improve the prediction of the characteristics of an eddy current damping, the induced magnetic flux densities have to be considered in following researches.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.2
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• pp.71-82
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• 2011

Electronic display markets has been developed. The cathode ray tube of brown form recently celebrated their 100th by first display. Also LCD of flat form recently celebrated their 25th by second display and it has advantage of small volume, lower consumption power. But FPD has problem that is property of brittle and noncarrying by glass substrate. Therefore the arrival of portable electronics devices has put an increasing premium on durable, lightweight and inexpensive display components. It is flexible display by third display. Also electronics field such as printed wiring board, RFID, membrane switch prefer flexible display. The conductive pattern can be used mostly in field of electronic displays and electronics. This manufacture of conductive pattern in present used is screen printing. The the conductive pattern. It has advantages of flexibility, high conductivity, drying in low temperature, good conductivity. screen printing has problem that is low productivity and use not flexible substrate because of high fire temperature. This study was developed novel method to form the conductive pattern. It has advantages of flexibility, high conductivity, drying in low temperature, good conductivity.

• Solar Energy
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• v.20 no.1
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• pp.81-89
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• 2000

In the present study, the characteristics of conductive and convective heat transfer occurred in a circular absorber of PTC (parabolic trough concentrator) for medium temperature solar energy utility were numerically investigated. A circular tube was considered as an absorber and the shape of PTC modeled in this study was based on the system that was installed in Korea Institute of Energy Research. Not only convection inside the tube but also conduction through the wall of the tube were analyzed, simultaneously. Circumferentially non-uniform heat flux that was simulated from the non-uniform solar disc model proposed by Jose was applied as thermal boundary condition on the tube surface. And, hydrodynamically fully developed laminar velocity profile was used as the inlet boundary condition and it was assumed that the working fluid was water. And, local heat fluxes at the interface of the tube and the working fluid were calculated for different wall thickness and thermal conductivity of the tube at various Reynolds number. Based on the results, the effects of thermal conduction of the tube on the local heat transfer were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.145-146
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• 2006

The most Important research topic in the development of ZnO LED and LD is the production of p-type ZnO thin film that has minimal stress with outstanding stoichiometric ratio. In this study, Phosphorus diffused into the undoped ZnO thin films using the ampoule-tube method for the production of p-type znO thin films. The undoped ZnO thin films were deposited by RF magnetron sputtering system on $GaAs_{0.6}P_{0.4}$/GaP and Si wafers. 4N Phosphorus (P) was diffused into the undoped ZnO thin films in ampoule-tube which was performed and $630^{\circ}C$ during 3hr. We found the diffusion condition of the conductive ZnO films which had p-type properties with the highest mobility of above 532 $cm^2$/Vs compared with other studies PL spectra measured at 10K for the purpose of analyzing optical properties of p-type ZnO thin film showed strong PL intensity in the UV emission band around 365nm ~ 415nm and 365nm ~ 385nm.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.768-774
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• 2006

The microstructure of Ni-YSZ cermets was controlled with fine and coarse starting powders (NiO and YSZ) to obtain a optimum strong and conductive tubular anode support for SOFCs. Three types of cermets with different microstructures, i.e., coarse Ni-fine YSZ, fine Ni-coarse YSZ, and fine Ni-fine YSZ, were fabricated to investigate their electrical and mechanical properties. The cermets from fine NiO powder showed high electrical conductivity due to the enhanced percolation of Ni particles. The cermet by foe Ni and coarse YSZ showed excellent electrical conductivity (>1000 S/cm) despite its high porosity $(\sim40%)$ but it showed poor mechanical strength due to the lack of percolation by YSZ particles and due to large pores. Thus fine NiO and YSZ powders were used to make strong and conductive Ni-YSZ support tube by extrusion. The microstructure of the anode tube was modified by the amount of polymeric additives and carbon black, a pore former. Ni-YSZ tube (porosity $\sim34%$) with the finer microstructure showed better performance both in electrical conductivity (>1000 S/cm) and fracture strength $(\sim140\;MPa)$. Either flat or circular NiO-YSZ tubes with the length from 20 to 40cm were successfully fabricated with the optimized composition of materials and polymeric additives.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.250-254
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• 2008

Eddy currents are induced when a nonmagnetic conductive material is moving subjected to the magnetic field due to a permanent magnet. These currents circulates in the conductive material and are dissipated, causing a repulsive force between the magnet and the conductor. Using this concept, the eddy current damping can be used as a viscous damping. The present study investigates the characteristics of a magnetic damping analytically and experimentally. The theoretical model of a eddy current damping is developed from electromagnetics and is verified from experiments. The drop test of a magnet in the cooper tube shows that the present model can accurately predict the damping force. Additionally, the dynamic test of a eddy current damping is carried to verify the present model.