• Journal of Powder Materials
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• v.10 no.5
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• pp.344-347
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• 2003

Pure tantalum powder has been produced by combining Na as a reducing agent, $K_2$TaF$_{7}$ as feed material, KCl and KF as a diluent in a stainless steel (SUS) bomb, using the method of metallothermic reduction. And we examined various types of after-treatment that affect the high purification of powder. A significant amount of impurities contained in recovered powder was removed in various conditions of acid washing. In particular, 20% (HCl + HNO$_3$) was effective in removing heavy metal impurities such as Fe, Cr and Ni, 8% H$_2$SO$_4$ + 8% $Al_2$(SO$_4$)$_3$ in removing fluorides such as K and F from non-reactive feed material, and 2% $H_2O$$_2$ + 1 % HF in removing oxides that formed during reaction. Significant amounts of oxygen and part of light metal impurities could be removed through deoxidation and heat treatment process. On the other hand, because it is difficult to remove completely heavy metal impurities such as Fe, Cr, and Ni through acid washing or heat treatment process if their contents are too high, it is considered desirable to inhibit these impurities from being mixed during the reduction process as much as possible.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.299-302
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• 2003

The interface heat transfer coefficient was measured for non-isothermal bulk forming of Ti-6Al-4V. FE analysis and experiments were conducted. Equipment consisting of AISI H13 die was instrumented with thermocouples located at sub-surface of the bottom die. Die temperature changes were investigated in related to the process variables such as reduction, lubricant and initial die temperature. The calibration approach based on heat conduction and FE analysis using an inverse algorithm were used to evaluate the interface heat transfer between graphite-lubricated die and glass-coated workpiece. The coefficients determined determined were affected mainly by the contact pressure. The validation of the coefficients was made by the comparison between experimental data and FE analysis results.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.1
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• pp.16-25
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• 2003

Recently, semi-solid forming (SSF) Process has been applied in many automobile parts for improved weight reduction, better environmental protection and energy savings. SSF process was well developed for high volume production of light weight aluminum components. In this paper, knuckle has been manufactured by SSF and then the microstructures and mechanical properties were investigated followed by various heat-treatment conditions. It was found that the examined microstructure was equiaxed at the whole cross-section area.

• Journal of Environmental Science International
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• v.22 no.4
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• pp.425-433
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• 2013

A mass balance of process was calculated by using the analysis of basic unit and environmental assessment of all the processes of Busan fashion color industry cooperative that operates a combined heat and power plant and a bio treatment plant. The mass balance for the combined heat and power plant was done, based on boiler and water treatment processes while each unit reactor was used for the bio treatment plant. From the results above, a resource recycle network, a treatment flowchart for food waste water/wastewater treatment and a carbon reduction program were established.

• Journal of Powder Materials
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• v.3 no.1
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• pp.13-24
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• 1996

Two grades of Permalloy strips, Fe-45Ni(PB) and Fe-78Ni-4Mo-5Cu(PC) were fabricated by powder rolling process from elemental powder mixtures. The roll compacted green strips were sintered, homogenized, cold rolled with or without an intermediate annealing and finally heat treated to measure magnetic properties. For a given thickness reduction, rolling with an intermediate annealing was found more effective to achieve a full densification with no visible micropores and also to obtain better magnetic properties. Increasing the final rolling reduction also produced a marked improvement of the magnetic properties whereas the cooling rate during the final heat treatment has little effect in both grades. Addition of a small amount, 0.4% Mn slightly degraded the properties. As an overall, The PM strips produced via powder rolling yielded the similar soft magnetic properties to the corresponding commercial grades produced via wrought processing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.82-90
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• 2019

This analysis demonstrates the effective removal of heat generated from a solar panel's output degradation factor solar cells (the solar panel's output deterioration factor), and solves the problems of oxidation and corrosion in existing metal heat sinks. The heat-dissipating test specimen was prepared using carbon materials; then, its thermal conductivity and its effectiveness in reducing temperatures were studied using heat transfer numerical analysis. As a result, the test specimen of the 30g/㎡ basis weight containing 80% of carbon fiber impregnated with carbon ink showed the highest thermal conductivity 6.96 W/(m K). This is because the surface that directly contacted the solar panel had almost no pores, and the conduction of heat to the panels appeared to be active. In addition, a large surface area was exposed to the atmosphere, which is considered advantageous in heat dissipation. Finally, numerical analysis confirmed the temperature reduction effectiveness of 2.18℃ in a solar panel and 1.08℃ in a solar cell, depending on the application of heat dissipating materials.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.462-468
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• 1984

The variation of thermal diffusivity with respect to rolling reduction is experimentally determined by flash technique. Copper alloy is used as an experimental and specimens are cut from the slab produced by rolling process with different percent reduction in thickness along the rolling direction and with 30.deg. 60.deg. and 90.deg. angle to the rolling direction. It is found that thermal diffusivity is slightly decreased as rolling reduction increased, and it has tendency that thermal diffusivity is increased slightly as its angle approached to 90.deg. at same rolling reduction.

• Transactions of Materials Processing
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• v.31 no.2
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• pp.57-63
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• 2022

The current study performed formability analysis of a heat exchanger separator for an electric vehicle to apply a high-strength aluminum sheet based on parametric analysis. Mechanical properties for sheet metal forming simulation were evaluated by tensile test, bulge test, and Nakajima test. Two-stage crash forming was established by considering the mass production process using conventional low-strength aluminum sheets. In this study, FEM for the two-stage forming process was conducted to optimize the corner radius and height for improving the formability. In addition, the possibility of a one-stage forming process application was confirmed through FEM. The prototype of the sample was manufactured as FEM results to validate the parametric analysis. Finally, this result can provide a one-stage forming process design method using the high-strength aluminum sheet for weight reduction of a heat exchanger separator for an electric vehicle.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.81-91
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• 2013

A novel design process of a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant of about $100^{\circ}C$ but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance. The number of pass, the arrangement of the tubes of each pass, and the positions of the inlet and outlet ports on the header are most critical parameters affecting the flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. An example is presented through the proposed design process and compared with an experiment.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.260-269
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• 2020

The Steam Assisted Gravity Drainage (SAGD) process is an enhanced method to extract oil from bitumen which involves surface and central process facilities. This paper describes the Central Process Facilities (CPF) of SAGD and proposes several retrofit plans to the Heat Exchanger Network (HEN). In this approach, the process integration scheme is applied to estimate the energy saving in HENs, and various cases are modeled in favor of a commercial simulator. Throughout this work, a minimum approach temperature of 10℃ is assumed. The results reveal that, due to the HEN optimization using process integration, the heating and cooling duties can be reduced to 29.68MW and 1.886MW, respectively. Compared with the Husky case, all cases considered in this study indicate a potential reduction of at least 6% in total cost, including investment and operation costs.