• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.429-434
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• 2012

Ignition delay of micro/nano aluminum particles is caused by aluminum oxide shell. The method of minimizing this ignition delay is proposed in the study. Generating and heating of particles are processed at the same time. As soon as heated particles are produced, they immediately contact with oxygen. Chemical reaction is induced on the contact surface instead of crystallization of oxide shell. Finally particles are ignited. Aluminum particles are generated by laser ablation on an aluminum plate using Nd:YAG pulse laser. Injected particles are confirmed through visualization of particles using scattering method. $CO_2$ continuous laser supplies heat to aluminum plate and generated particles. Trace of burning particles is observed in the experiment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.295-303
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• 2008

The objectives of this study are to predict actual system performance and effective operating range of the 2-stage compression heat pump system using river water. An electronic expansion valve was applied to the simulation to analyze the effects of operating conditions on the system performance. The developed program was verified by comparing the predictions with the measured data. The results from the present model showed a good agreement with the measured data. In addition, the heat pump simulation was conducted by increasing condenser reservoir inlet temperature to investigate the benefits of the 2-stage compression over the 1-stage compression in the heating mode. The performance of the 2-stage compression cycle was better than that of the 1-stage compression when the inlet temperature of the condenser reservoir was higher than $40^{\circ}C$.

• Journal of the Korean Solar Energy Society
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• v.34 no.3
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• pp.75-81
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• 2014

Recently, the use of renewable energy has been attracted due to the interest in energy-saving and the reduction of CO2 emission. In order to reduce the energy consumption of the cooling and the heating in the field of the architectural engineering, heat pump systems using renewable energy have been developed and used in various applications. In many researches, integrated heat pump systems are suggested which use solar and geothermal heat as the heat source for cooling and heating. However, it is still difficult to predict the performance of the systems, because the characteristic of heat exchange in each system is complicated and various. In this system, the performance prediction simulation of the heat pump was developed using a dynamic simulation model. This paper describes the summary of the suggested systems and the result of the simulation. The average temperature of the heat source, heating loads and COP were calculated with the cases of different local conditions, different system composition and different operation time by TRNSYS 17.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.914-922
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• 2004

In this study, measurement and analysis of energy consumption of a research building have been conducted. The energy audit procedure includes monitoring of electricity and LNG consumption over a period of three yews from 2000 to 2002. Data acquisition system for collecting energy consumption data of HVAC equipment such as chillers, fan filter units, AHUs, cooling towers, boilers, pumps, fan coil units, air compressors and etc. has been installed in a building located in Seoul. Data collected at an interval of 1 minute are analyzed for studying the energy consumption pattern of a research building. Percentage of energy consumption of all HVAC equipment is $51.0\%$ in 2000, $55.4\%$ in 2001, and $62.3\%$ in 2002, respectively. Electricity consumption of chillers accounts for $17.6\%$ of the total energy consumption, which is the largest. Annual energy consumption-rate per unit area is $840.5Mcal/m^2{\cdot}y$ in 2000, $1,064.8Mcal/m^2{\cdot}y$ in 2001, and $1,393.0Mcal/m^2{\cdot}y$ year 2002, respectively.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.209-214
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• 2006

In this study, application of groundwater thermal energy by use of riverbank filtration(RBF) system is reviewed and checked as an energy resources. Also, the cooling and heating system using RBF was developed in Chang-Won Waterwork site to examine the feasibility in real operation of the system. We estimates the roughly overall energy obtained from RBF system if the system is used in cooling and heating. The water temperature and room temperature have been monitored to evaluate the efficiency of the system and the preliminary results show that the geothermal energy obtained by RBF could be adopted in cooling and heating energy source efficiently.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1117-1125
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• 2004

In this study, in order to utilize the waste heat of industrial wastewater in the range of the relatively low temperature of 40～5$0^{\circ}C$ as a heat source, a hybrid heat pump system was considered by computer simulation method. In the simulation, an absorber, desorber and solution heat exchanger were modelled by UA values while a compressor and pump performance were specified by an isentropic efficiency. Simulation results show that the performance of hybrid heat pump can be up to 80% higher than that of conventional R134a heat pump when it makes a process hot water of 9$0^{\circ}C$ while the wastewater is cooled down to 2$0^{\circ}C$. As the absorber pressure increases, the system performance and deserter pressure increase with a favorable effect of a compressor discharge gas temperature drop.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.701-706
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• 2006

Groundwater heat pump systems are the oldest of the ground-souce systems and it has various type. Standing column well type are must be located in hard rock geology site and produce sufficient water for the conventional open loop system. These system are indirect type(the building circulating loop and ground water are intercept). Existence of the exchanger the foundation protect water quality to use of open loop. The design of open loop system are concern on the power requirements. An experimental study was analysis the extremely heating operation COP of ground water heat pump system. Operation efficiency of the 50RT systems shows that, COP $2.9{\sim}5.0$ in heating operation. And generally it shows 3.4.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.215-220
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• 2006

Along with socioeconomic development and improving standard of living, the heat demand for heating and cooling in residential and commercial sectors is expected to expand rapidly, reaching over 43 million TOE by 2010 in Korea(about 80% increase compared with that in 1995). Since most of this heat demand is loop temperature below $60^{\circ}C$, the utilization of 'unused energy' is surely one of very effective measures to both environmental preservation and energy conservation. 'Unused energy' in this paper is implicated as 'temperature differential energy' available from treated sewage water, useful and abundant heat source for heat pump(cooler in summer and warmer in winter than outside air). An analysis was carried out to estimate the energy potential of treated sewage water for heat pump heat source. Some analysis were taken to study the characteristics of a heat pump system using the treated sewage water as heat source.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.3
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• pp.442-447
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• 2011

Co-incorporation of Leguminosae with Gramineae could reduce the risk of nitrogen starvation phenomena caused by appling green manure of Gramineae alone. The objective of the study was to examine the effect of mixed sowing of hairy vetch and rye seeds on soil quality in mountainous highland. Mixed sowing of hairy vetch and rye increased the yield of green manure and nutrients compared with those for sowing of hairy vetch or rye alone. The yield of green manure from row seeding was $5.3Mg\;ha^{-1}$ compared with $4.8Mg\;ha^{-1}$ for broadcast seeding. Incorporation of the two green manure crops increased yield of red-bean by 58~92% as compared with yield for incorporation of rye alone. The results obtained in the study imply that mixed sowing of hairy vetch and rye can solve the problem of low emergence of hairy vetch in spring and high C/N ratio and rough incorporation of rye, in addition to increase in yield of green manure.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.226-232
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• 2021

The relationship between precipitation and coefficient of thermal expansion of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments were studied by the thermodynamic analyzer (TMA) and differential scanning calorimetry (DSC). Solution heat treatment of the alloy was carried out at 535℃ for 6 h followed by water quenching, and the samples were artificially aged in the air at 180℃ and 220℃ for 5 h. The coefficient of thermal expansion (CTE) curve showed some residual strain and decreased with increasing aging temperature. The CTE curves changed sharply in the temperature range of 200℃ to 400℃, and the corresponding peak shifted for the aged samples due to the change in the precipitation behavior of the secondary phase. These transformation peaks in the aged sample are related to the volume of the precipitation of the Si phase as determined by DSC analysis. The change in CTE is mainly caused by the precipitation of the Si phase in the Al-Si alloy, and the size of the change occurs simultaneously with the size of the precipitate.