• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.1
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• pp.7-12
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• 2012

This study proposes a hybrid geothermal system combined with heating mode and snow-melting mode for winter season in order to increase the annual operating efficiency of the GSHP(Ground Source Heat Pump). The purpose of this study is to get effectiveness of the hybrid geothermal system by the site experiments. In case of snow-melting only mode, the GSHP COP is 0.7 higher than system COP in average. And in case of hybrid mode, heating GSHP COP is 0.5 higher than snow-melting GSHP COP. And it is also found out that all COP obtained through measurement periods is higher than nominal COPs given by GSHP manufacturer. As a conclusion, it is clear that the proposed hybrid geothermal system is expected as a highly efficient system.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.32-35
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• 1989

A 150W industrial Nd:YAG laser was developed. The thermal lensing effect was examined and the radius and position of rear mirror were optimized for higher efficiency. The efficiency of 2.5% was achieved. Also, the performance of laser welding in fine thermocouples and between high-temperature-melting dissimilar metals were investigated.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2285-2290
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• 2007

The main objective of this study is to analyze the heat transfer characteristics in the electric melting furnace. Local temperatures are measured at various location in the furnace using the B-type thermocouples. In this paper, the numerical simulation was performed using the ANSYS software, and compared with experimental data. Mathematical heat transfer model for the prediction of temperature distribution has been developed by considering the thermal radiation among heating element, crucible and insulating materials. The results show that the temperature distributions predicted by the numerical simulation agree with experimental results comparatively.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.796-803
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• 2001

Numerical solutions for the convection-dominated melting in a rectangular cavity are presented. The enthalpy-porosity model is employed as the mathematical model. This model is applied in conjunction with the EIT method to detect boundary movement in a phase changing environment. The absorption and evolution of latent heat during the phase change is dealt with by the enthalpy-based energy equation. This seems to be more efficient than resolving the temperature-based energy equation. The velocity switch-off, which is required when solid changes into liquid, is modeled by the porous medium assumption. For efficiency and simplicity of the solutions procedure, this paper proposes a simple algorithm, which iterates the temperature and the liquid fraction of the cells comprising the front layer. The numerical results agree reasonably well with the experimental data and other previous works using the transformed-grid system.

• Resources Recycling
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• v.13 no.4
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• pp.46-52
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• 2004

The present main research direction of waste treatment is the development of incineration system for low pollution. Also, heat value of waste is increased because of the rising of living standard, environmental consideration and collection of sorted waste for recycling. Therefore, many researches have been continued for solving ash problem including heavy metals, dioxin problem and high energy efficiency by use of high heat value. This study is described for the facilities of pyrolysis system, pyrolysis-melting system, pyrolysis-gasification melting system.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.165-170
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• 2004

• Resources Recycling
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• v.21 no.4
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• pp.69-75
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• 2012

Destruction of HFC-134a from ELV (End of Life Vehicle) were determined in a gasification-melting demonstration system of municipal solid waste (100ton/day). The injection system has been developed for the uniform injection of HFC-134a to the gasification-melting system. The destruction characteristics of HFC-134a and analysis of exhaust gases have been performed. The destruction efficiency was 99.995% for HFC-134a feeding of 3 kg/hr and the exhaust gases such as CO, SOx, NOx, HCl and HF satisfied the environmental standards.

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.201-207
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• 2007

In some manufacturing industries, there are many situation in which the simultaneous monitoring or control of two or more related quality characteristics is necessary. However, monitoring these two or more related quality characteristics independently can be very misleading. When several characteristics of manufactured component are to be monitored simultaneously, multivariate $x^2$ or $T^2$ control chart can be used. In this paper, establishing a early warning system(EWS) using multivariate control charts to analyze early out-of-control signals in melting process with many quality characteristics was presented. This module which we developed to control several characteristics improved efficiency and effectiveness of process control in the melting process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.93-98
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• 2019

Recently, with the development of the aerospace and automotive industries, the demand for high-melting-point materials has increased. However, high-melting-point materials are difficult to cut through conventional machining methods. Thermally assisted machining (TAM) is a method for improving the machinability by preheating the materials. A laser, the most commonly used device for TAM, has high efficiency through local preheating but is not sufficient for maintaining a high preheating temperature due to rapid cooling. However, the use of multi-heat sources can supplement the disadvantage of a single heat source. The high preheating temperature can be maintained with a wide and deep heat-affected zone (HAZ) by multi-heat sources. The purpose of this study is to analyze the preheating effects of multi-heat sources using laser plasma. Thermal analysis and preheating experiments were carried out. As a result, the high preheating effect of multi-heat sources compared with a single heat source was verified.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.649-657
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• 1998

In this study, the effects of the various conditions of frosting and defrosting on the behavior of defrosting in a fin-tube heat exchanger have been examined experimentally. The electric heater is used for defrosting in a fin-tube heat exchanger It is shown that there are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after the completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering the degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of the frost irrespective of the frosting condition. The defrosting behavior is affected by the frosting density as well as the frost accumulation, which vary with the experimental operating conditions during the frosting period. The heat loss to the surrounding air decreases, and the melting and defrosting efficiencies show high values with decreasing heat input.