• Journal of Power System Engineering
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• v.17 no.2
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• pp.70-77
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• 2013

An experimental study was carried out to understand the heat transfer performance of a miniature loop heat pipes using water-based copper nanoparticles suspensions as the working fluid. The suspensions consisted of deionized water and copper nanoparticles with an average diameter of 80 nm. Effects of the cupper mass concentration and the operation pressure on the average evaporation and condensation heat transfer coefficients, the critical heat flux and the total heat resistance of the mLHPs were investigated and discussed. The pressure frequency also depends upon the evaporator temperature which has been maintained from $60^{\circ}C$ to $90^{\circ}C$. The Investigation shows 60% filling ratio gives the highest inside pressure magnitude of highest number pressure frequency at any of setting of evaporator temperature and 5wt% results the lowest heat flow resistance.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.3
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• pp.32-38
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• 2005

Electrical discharge machining is the method of using thermal energy by electrical discharge. Generally, if the material of workpiece has conductivity even though very hard materials and complicated shape which are difficult to cut such as quenching steel, cemented carbide, diamond and conductive ceramics, the EDM process is favorable one of possible machining processes. But, the process is necessarily required of finish cut and heat treatment because of slow cutting speed, no mirror surface, brittleness and crack due to the residual stress for manufactured goods. In this experimental thesis, the super EDM drilling was developed for high precision semiconductor die steel and for minimization of leadframe width. It was possible to development of EDM drilling machine for high precision semiconductor die with the electrode guide and its modelling and stress analysis. The development of electrode with the copper pipe type was conducted to drill the hole from the diameter of 0.1mm to 3.0mm with the error of from 0.02mm to 0.12mm. From the SEM and EDX analysis, the entrance of the EDM drill was found the resolidification of not only the component of tungsten but also the component of copper.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.542-549
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• 2008

The evaporation heat transfer coefficient and pressure drop of R-22 and R-407C in a horizontal copper tube were investigated experimentally. The main components of the refrigerant loop are a receiver, a compressor, a mass flow meter, a condenser and a double pipe type evaporator (test section). The test section consists of a smooth copper tube of 6.4 mm inner diameter. The refrigerant mass fluxes were varied from 100 to $300\;kg/m^2s$ and the saturation temperature of evaporator were $5^{\circ}C$. The evaporation heat transfer coefficients of R-22 and R-407C increase with the increase of mass flux and vapor quality. The evaporation heat transfer coefficients of R-22 is about $5.68{\times}46.6%$ higher than that of R-407C. The evaporation pressure drop of R-22 and R-407C increase with the increase of mass flux. The pressure drop of R-22 is similar to that of R-407C. In comparison with test results and existing correlations, correlations failed to predict the evaporation heat transfer coefficient of R-22 and R-407C. therefore, it is necessary to develope reliable and accurate predictions determining the evaporation heat transfer coefficient of R-22 and R-407C in a horizontal tube.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.481-489
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• 2010

Experiments on laminar mixed convection in a vertical pipe were performed for the Re range 1,000-3,000, the $Gr_H$ range $10^5-10^8$, the Pr range 2,000-7,000, and aspect ratio range 1-7. Using the analogy concept, heat transfer systems were simulated by mass transfer systems. A cupric acid.copper sulfate electroplating system was adopted as the mass transfer system, and the mass transfer rates were measured. The measured Nu values were far greater than those previously reported because of the large value of pr in this experiment. As the aspect ratio in this study was not sufficiently large for the flow to be fully developed, the test results were similar to those for mixed convection on a vertical plate rather than that inside a long vertical pipe. It was concluded that the behavior of laminar mixed convection of a developing flow in a vertical pipe at a low aspect ratio and low $Gr_H$ is similar to that of laminar mixed convection in the vertical plate. As the aspect ratio and $Gr_H$ increase, the laminar mixed convection phenomena becomes similar to that observed in a fully developed flow in the vertical pipe.

• Transactions of Materials Processing
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• v.20 no.7
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• pp.473-478
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• 2011

In this study, the performance of a thermo siphon type radiator made of copper for LED lighting system was evaluated by using an inverse heat transfer method. Heating experiments and finite element heat transfer analysis were conducted for three different cases. The data obtained from experiments were compared with the analysis results. Based on the data obtained from experiments, the inverse heat transfer method was used in order to evaluate the heat transfer coefficient. First, the heat transfer analysis was conducted for non-vacuum state, without the refrigerant. The evaluated heat transfer coefficient on the radiator surface was 40W/$m^2^{\circ}C$. Second, the heat transfer analysis was conducted for non-vacuum state, with the refrigerant, resulting in the heat transfer coefficient of 95W/$m^2^{\circ}C$. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant. For the third case, the evaluated heat transfer coefficients were 140W/$m^2^{\circ}C$. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant. For the third case, the evaluated heat transfer coefficients were 140W/$m^2^{\circ}C$ for the radiator body, 5W/$m^2^{\circ}C$. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant for the rising position of radiator pipe, 35W/$m^2^{\circ}C$. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant. For the highest position of radiator pipe, and 120W/$m^2^{\circ}C$ for the downturn position of radiator pipe. As a result of inverse heat transfer analysis, it was confirmed that the thermal performance of the current radiator was best in the case of the vacuum state using the refrigerant.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.525-536
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• 2015

Trapiche project corresponds to the advanced exploration stage which is thought to be a part of various porphyry copper deposits occurring in the margin of Andahuyalas-Yauri metallogenic belt. This deposit is genetically related to the monzonitic porphyry intrusion and Oligocene breccia pipe. Mineralization consists of primary sulfides such as pyrite, chalcopyrite, bornite, and molybdenite and secondary sulfides such as chalcocite, covellite and digenite. It occurs malachite, tenorite and cuprite as copper oxide. As a result of lixiviation or enrichment process, mineralization shows untypical zonation structure. Breccia and porphyry areas characterize the vertical zonation patterns. In the northern area, lixiviation zone, secondary enrichment zone, transitional zone and primary mineralized zone are distributed in northern area. In the western area of deposit, oxidation zone and mixed zones are narrowly occurred. Inferred resources of deposit is estimated to be 920 Mt @ 0.41% Cu with the cut-off grade of 0.15%.

• Applied Science and Convergence Technology
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• v.24 no.4
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• pp.77-83
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• 2015

Many welding processes are performed to construct cryogenic system. Leak-tight for the cryogenic system is required at low temperature environment. Helium leak detection techniques are commonly used to find leak for the cryogenic system. The helium leak detection techniques for spraying, sniffing and pressurizing techniques are introduced. High vacuum is also necessary to use helium leak detector. So, types of fluid flow, effective temperature, conductance and pumping speed are introduced for vacuum pumping. Leak test procedure is shown for pipe welding, cryomodule and low temperature test. Cryogenic seals which include copper gasket, helicoflex gasket and indium are investigated.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.572-578
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• 2001

This study is to research the heat transfer characteristics in copper-water heat pipes with screen wick, #100. Recently, the semiconductor capacity of an electronic unit has been larger, on the contrary, its size is smaller than before. As a result, a high-performance cooling system is needed. Experimental variables are inclination angle and temperature of cooling water. The distilled water was used for the working fluid. At a inclination angle ${-6}^{\circ}$, #100 2layer screen mesh is shown the best heat transfer performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.322-325
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• 2007

This paper suggests a non-contact sensor for measuring bending vibration of a non-metallic cylinder in two orthogonal directions simultaneously. Recent research shows that a solenoid can pick up bending vibrations of a nonmetallic cylinder based on the reversed Lorentz force mechanism if an electrical conductive patch is attached to the cylinder. In this work, pairs of specially designed patches are used to make two independent paths for the current induced by bending vibrations, which enables the measurement of bending vibrations along two orthogonal directions simultaneously. The working performance of the developed sensor was verified by using two accelerometers.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.126-136
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• 1995

Copper magnetron anode of a microsave-over consists of an cylindrical outer-tube and various inner-vanes. The magnetron anode is produced by the complex processes; vane blanking, pipe cutting and silver-alloy brazing of vanes. Recently, the backward extrusion process for forming vanes has been developed to avoid the complex procedures. The developed process is analyzed by using upper-bound elemental technique (UBET). In the UBET analysis, the upper-bound load, the configuration and the vane-height of final extruded product are determined by minimizing the roral power consumption with repect to chosen parameters. To verify theoretical analysis, experiments have been carried out with pure plasticine billets at room temperature, using different web-thickness and number of vanes. The theoretical predictions both for forming load and vane-height are in reasonable agreement with the experimental results.