• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.11
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• pp.581-586
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• 2015

In this study, an analysis was performed on the performance of the solar water heating system with geo-thermal heat pump for a detached house. This system has a flat plate solar collector ($8\;m^2$) and a 3 RT heat pump. The heat pump acts as an auxiliary heater of the solar water heating system. These systems were installed at four individual houses with the same area of $100\;m^2$. The monitoring results for one year are as follows. (1) The average daily operating time of the solar system appeared to be 313 minutes in spring (intermediate season), and 135 minutes and 76 minutes in winter and summer respectively. The reason for the short operating time in summer is the high storage temperature due to low water heating load. The high storage temperature is caused by a decrease in collecting efficiency as well as by overheating. (2) The geothermal heat pump as an auxiliary heater mainly operates on days of poor insolation during the winter season. (3) Despite controlling for total house area, hot water consumption varies greatly according to the number of people in the family, hot water usage habits, etc. (4) The yearly solar fraction was 69.8 to 91.5 percent, which exceeds the maximum value of 80% as recommended by ASHRAE. So the solar collector area of $8\;m^2$ appeared to be somewhat greater for the house with an area of $100\;m^2$. (5) The observed annual efficiency of solar systems was relatively low at 13.5 to 23.6%, which was analyzed to be due to the decrease in thermal efficiency and the overheating caused by a high solar fraction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.457-463
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• 2012

Current refrigerators are designed to have thin doors and walls to facilitate user convenience and increase inner storage space. However, the thin doors and walls gives rise to the problem of dew generation on the outer surface of a refrigerator due to a large critical temperature difference between the outer wall and the room air; So far, an electric heater is commonly used for making the dew to evaporate; in this case, the heater inevitably requires additional electrical power. We propose a new approach to reduce the dew generation in a refrigerator by redesigning the gasket and varying the thickness of the inner case of the refrigerator. The results of simulations performed in this study indicate that the surface temperature in the region where dew was generated was increased by approximately $0.39{\sim}3.07^{\circ}C$ without the use of a heater.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.108-109
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• 2012

This talk will begin with the demonstration of facile synthesis of silicon nanostructures using the magnesiothermic reduction on silica nanostructures prepared via self-assembly, which will be followed by the characterization results of their performance for energy storage. This talk will also report the fabrication and characterization of highly porous, stretchable, and conductive polymer nanocomposites embedded with carbon nanotubes (CNTs) for application in flexible lithium-ion batteries. It will be presented that the porous CNT-embedded PDMS nanocomposites are capable of good electrochemical performance with mechanical flexibility, suggesting these nanocomposites could be outstanding anode candidates for use in flexible lithium-ion batteries. Directed self-assembly (DSA) of block copolymers (BCPs) can generate uniform and periodic patterns within guiding templates, and has been one of the promising nanofabrication methodologies for resolving the resolution limit of optical lithography. BCP self-assembly processing is scalable and of low cost, and is well-suited for integration with existing semiconductor manufacturing techniques. This talk will introduce recent research results (of my research group) on the self-assembly of Si-containing block copolymers for the achievement of sub-10 nm resolution, fast pattern generation, transfer-printing capability onto nonplanar substrates, and device applications for nonvolatile memories. An extraordinarily facile nanofabrication approach that enables sub-10 nm resolutions through the synergic combination of nanotransfer printing (nTP) and DSA of block copolymers is also introduced. This simple printing method can be applied on oxides, metals, polymers, and non-planar substrates without pretreatments. This talk will also report the direct formation of ordered memristor nanostructures on metal and graphene electrodes by the self-assembly of Si-containing BCPs. This approach offers a practical pathway to fabricate high-density resistive memory devices without using high-cost lithography and pattern-transfer processes. Finally, this talk will present a novel approach that can relieve the power consumption issue of phase-change memories by incorporating a thin $SiO_x$ layer formed by BCP self-assembly, which locally blocks the contact between a heater electrode and a phase-change material and reduces the phase-change volume. The writing current decreases by 5 times (corresponding to a power reduction of 1/20) as the occupying area fraction of $SiO_x$ nanostructures varies.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.103-108
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• 2016

Carbon Capture and Storage technologies are recognized as key solution to meet greenhouse gas emission standards to avoid climate change. Although MEA (monoethanolamine) is an effective amine solvent in $CO_2$ capture process, the application is limited by high energy consumption, i.e., reduction of 10% of efficiency of coal-fired power plants. Therefore the development of new solvent and improvement of $CO_2$ capture process are positively necessary. In this study, improvement of $CO_2$ capture process was investigated and applied to Test Bed for reducing energy consumption. Previously reported technologies were examined and prospective methods were determined by simulation. Among the prospective methods, four applicable methods were selected for applying to 0.1 MW Test Bed, such as change of packing material in absorption column, installing the Intercooling System to absorption column, installing Rich Amine Heater and remodeling of Amines Heat Exchanger. After the improvement construction of 0.1 MW Test Bed, the effects of each suggested method were evaluated by experimental results.

• Design & Manufacturing
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• v.10 no.2
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• pp.18-23
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• 2016

Injection molded thermoplastic parts may need to be coated to facilitate paint adhesion, or to satisfy other surface property requirements, such as appearance, durability, and weather resistance. In this paper, a two-component polyurethane metering system was developed for the simultaneous injection and surface coating of a plastic substrate. The system was composed of storage tanks, feed pumps, axial piston pumps, mixing head. The tank was designed to be double-jacket structured and fabricated for polyol and isocyanate, respectively. A temperature chamber was used to maintain the material temperature to be $80^{\circ}C$ during flowing from storage tank to mixing head. Inside the chamber, feed pump, low pressure filter, high pressure pump, high pressure filter, pressure sensor, flow meter were installed. A mixing head of L-type was used for homogeneous mixing of polyol and isocyanate. Inside the mixing head, a cartridge heater and a temperature sensor were installed to control the temperature of the materials. The flow rate of axial-piston pump was controlled by using closed-loop feedback control algorithm. The input flow-rates were compared with the measured values. The output error was 6.7% for open-loop control, whereas the error was below 2.2% for closed-loop control. In addition, the pressure generated through mixing-head nozzle increased with increasing flow rate. It was found that the pressure drop between metering pump and mixing-head nozzle was almost 10 bar.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1905-1912
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• 2017

In recent years, Ulaanbaatar, a capital of Mongolia has witnessed major problem that air quality reaches hazardous level during the winter season. Coal combustion for heating of every house in "Ger" district is main reason. One way to reduce the air pollution is mass usage of electric heater. However, there are several difficulties such as overload and degradation of transformers and other equipment used in distribution and transmission systems as well as power shortage occurrence in evening peak period due to residential consumption. This study aims to contribute for solving the air pollution and power shortage problem in Mongolia. One possible solution could be distributed generation (DG) with photovoltaic (PV) penetration. In this study, PV with energy storage (ES) hybrid system to reduce peak load is analyzed. We proposed the suitable structure of PV-ES hybrid for Mongolian household, and suggested several operation scenarios. Optimal operation algorithm is carried out based on a comparison aspect from economical, grid impact and PV penetration possibility. The economic analyse shows annual income of 520USD, and has a payback period of 8 years for selected scenario. The proposed PV-ES system structure is verified by experimentation set on the building rooftop in city center. The suggested scenario is planned to apply for system in further research.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.3
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• pp.108-113
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• 2007

The performance of a solar water heater incorporating evacuated tubes was evaluated using a transient simulation program, TRNSYS. Simulations were performed for $60^{\circ}C$ of hot water load temperature and for 280 liter of daily hot water volumes and three 400 liter of storage tank volumes. Three patterns of daily hot water consumption profile were used in the present study (morning, lunch and evening). The results show that the increase in solar fraction depends on the load profile, as well as the collector efficiency coefficient. Hot water draw profile has a large effect on the performance of the SDHWS, the morning load profile has the highest solar fraction. The annual solar fraction of the system, at the weather conditions of Jinju is approximately 84% at lunch load pattern, the 280 kg of load volume, 400 kg of tank volume and the $60^{\circ}C$ of load temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.584-587
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• 2011

An internal flow aerodynamic test was performed for a Mach 5 scramjet engine. The test was done without fuel injection, as a preliminary test for the combustion test. Test engine is an engineering model with intake cross-section of $70mm{\times}200mm$ and total length of 1.7m. Test facility is a blowdown-type, high enthalpy, hypersonic facility. 19 pressures were measured through the holes on the model surface along the engine internal flow passage. It was found that the facility start is possible, and also supersonic flow is maintained inside the engine.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.457-463
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• 1999

The Joule-Thomson cryocooler with $H_2$gas has been developed. Cool-down characteristics and the cooling performance of a JT cryocooler have been investigated in detail. The JT cryocooler consists of JT expansion valve, heat exchanger, expansion chamber, compressed $H_2$gas storage tank, $LN_2$precooler, heater and a cryostat. The precooling process using both $GN_2$and $LN_2$was peformed to cool down the inside components of cryocooler under the maximum inversion temperature of $H_2$. The $H_2$expansion experiments have been peformed for 2-5MPa of H$_2$pressure to evaluate steady state temperatures of the cryocooler. It is found that the steady state temperatures are decreased as the H$_2$pressures are increased. The effects of cooling temperatures on the performance have been evaluated for various $H_2$and $N_2$pressures. It is seen that the cooling loads are increased, as the cooling temperature and operating pressure are increased.

• Journal of Information Display
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• v.10 no.3
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• pp.117-120
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• 2009

A new crystallization method for amorphous silicon, called selective area heating (SAH), was proposed. The purpose of SAH is to improve the reliability of amorphous silicon films with extremely low thermal budgets to the glass substrate. The crystallization time shortened from that of the conventional solid-phase crystallization method. An isolated thin heater for SAH was fabricated on a quartz substrate with a Pt layer. To investigate the crystalline properties, Raman scattering spectra were used. The crystalline transverse optic phonon peak was at about 519 $cm^{-1}$, which shows that the films were crystallized. The effect of the crystallization time on the varying thickness of the $SiO_2$ films was investigated. The crystallization area in the 400nm-thick $SiO_2$ film was larger than those of the $SiO_2$ films with other thicknesses after SAH at 16 W for 2 min. The results show that a $SiO_2$ capping layer acts as storage layer for thermal energy. SAH is thus suggested as a new crystallization method for large-area electronic device applications.