• International Journal of Fluid Machinery and Systems
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• v.9 no.1
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• pp.39-46
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• 2016

A high frequency hydraulic rock drill drifter with sleeve valve is developed to use on arm of excavator. In order to ensure optimal working parameters of impact system for the new hydraulic rock drill drifter controlled by sleeve valve, the performance test system is built using the arm and the hydraulic source of excavator. The evaluation indexes are gained through measurement of working pressure, supply oil flow and stress wave. The relations of working parameters to impact system performance are analyzed. The result demonstrates that the maximum impact energy of the drill drifter is 98.34J with impact frequency of 71HZ. Optimal pressure of YZ45 rock drill is 12.8 MPa-13.6MPa, in which the energy efficiency reaches above 58.6%, and feature moment of energy distribution is more than 0.650.

• The KSFM Journal of Fluid Machinery
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• v.18 no.2
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• pp.67-72
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• 2015

The purpose of this study is to achieve energy saving effect of inverter driving multistage centrifugal pump. For determining the operation points in the pump system, the system curves should be obtained experimentally. To get the system curves, three pumps combined in parallel and one pump operated with different rotational speeds. But for variable speed pump system, energy saving rates can not be evaluated from operation efficiencies. That is why operation efficiencies, system curves, duty cycles, and input powers of the pump system were measured by the constructed experimental apparatus. The duty cycle segmented into different flow rates and weighting the average value for each segment by the interval time. The system was operated with two different periods. The mean duty cycles were collected from apartment and found that the system operated at 40% and at 50% or below capacity. Measured energy saving rate was 58.16%. Estimating method of energy saving rate could be more effective operation index than that of operation efficiency.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.215-222
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• 2019

This work is experimental study of 10 kW specialized Combined Ocean Thermal Energy Conversion. We propose a C-OTEC technology that directly uses exhaust thermal energy from power station condensers to heat the working fluid (R134a), and tests the feasibility of such power station by designing, manufacturing, installing, and operating a 10 kW-pilot facility. Power generation status was monitored by using exhaust thermal energy from an existing power plant located on the east coast of the Korean peninsula, heat exchange with 300 kW of heat capacity, and a turbine, which can exceed enthalpy efficiency of 45%. Output of 8.5 kW at efficiency of 3.5% was monitored when the condenser temperature and seawater temperature are $29^{\circ}C$ and $7.5^{\circ}C$, respectively. The evaluation of the impact of large-capacity C-OTEC technology on power station confirmed the increased value of the technology on existing power generating equipment by improving output value and reducing hot waste water. Through the research result, the technical possibility of C-OTEC has been confirmed, and it is being conducted at 200 kW-class to gain economic feasibility. Based on the results, authors present an empirical study result on the 200 kW C-OTEC design and review the impact on power plant.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.92-97
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• 2008

To survive in outdoor environments, photovoltaic modules rely on packaging materials to provide requisite durability. We analyzed the properties of encapsulant materials that are important for photovoltaic module packaging. The properties of Ethylene Vinyl Acetate(EVA) sheet in photovoltaic encapsulant materials have to meet conditions that are high optical transmittance, good adhesion and high cross-linking rate. The objective of this paper is to understand the property evaluation methods of EVA sheet. Through this research, we could confirm that properties of EVA sheet have an effect on durability and operating efficiency of photovoltaic module.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.377-384
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• 2002

For economic evaluation of cooling plant equipments, it is necessary to simplify energy Prediction method, which should includes efficiency corrected by part-load ratio. This study proposed simplified method with regression equations of time-average partial loads and refrigerator capacity. DOE-2 Program was used to carry out a parametric study of twelve design variables. Five input variables were considered to be significant and were used in the regression equations. To test accuracy of simplified method, calculated results were compared with DOE-2 simulated results. Test result showes a good agreement with the simulation result with an error of 5.9∼7.6%. It is expected that this method can be used as an easy prediction tool for comparing energy use of different cooling plants during the early design stage.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.338-341
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• 2011

Water usage for cleaning the toilet bowl accounts for 27% of the total water usage. Water-saving valve that can select the amount of water for cleaning toilet bowl can be reduced expenditure. After installing water-saving valve, analysed the economic effects. Water-saving valves compared with flush valves, and researched the amount of water usage. Then analyzed fort he economic effects. Water-saving valve was used 5.6 ${\ell}/time$ for cleaning toilet bowl. In contrast, flush valve was consumed 8.4 ${\ell}/time$. Water-saving valve's water-saving rate was 33.3%. The initial payback period for Water-saving valve was 459.5 days. By a small investment in water saving valve, the economic benefits can be obtained.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.8
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• pp.177-184
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• 2019

Recently, electric power usages and peak loads from buildings are increasing due to higher outdoor air temperatures and/or abnormal climate during the summer period. As one of the eco-friendly measures, a renewable energy system has been received much attention. Particularly, interest on a photovoltaic (PV) system using solar energy has been rapidly increasing in a building sector due to its broad applicability. In using the PV system, one of important factors is the PV efficiency. The normal PV efficiency is determined based on the STC(Standard Test Condition) and the NOCT(Nominal Operating Cell Temperature) performance test. However, the actual PV efficiency is affected by the temperature change at the module surface. Especially, higher module temperatures generally reduce the PV efficiency, and it leads to less power generation from the PV system. Therefore, the analysis of the relation between the module temperature and PV efficiency is required to evaluate the PV performance during the summer period. This study investigates existing algorithms for calculating module surface temperatures and analyzes resultant errors with the algorithms by comparing the measured module temperatures.

• Journal of the Korean Society of Industry Convergence
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• v.16 no.4
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• pp.147-152
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• 2013

According to the obligation of BIM application, the guidelines of energy simulation based on BIM are being presented. Although there is the advantage to minimize the error in energy analysis using the energy model, there are still issues about insufficient standards and the compatibility of the gbXML. Therefore, it is necessary to establish the processes to utilize and apply BIM methods for energy simulation. This study was examined on the compatibility of data for energy simulation by the gbXML schema and energy efficiency by BIM.

• Journal of the Korean Electrochemical Society
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• v.26 no.4
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• pp.56-63
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• 2023

The development of renewable energy technologies, such as solar, wave, and wind power, has led to the diversification of water electrolysis technologies, which can be easily coupled with renewable energy sources in terms of economics and scale. Water electrolysis technologies can be classified into three types based on operating temperature: low-temperature (<100 ℃), medium-temperature (300-700 ℃), and high-temperature (>700 ℃). It can also be classified by the type of electrolyte membrane used in the system. However, the concepts of thermodynamic and thermo-neutral voltages calculations and are very important factors in the evaluation of energy consumption and efficiency of water electrolysis technologies, are often confused. This review aims to contribute to a better understanding of the calculation of operating voltage and efficiency of PEM water electrolysis technologies and to clarify the differences between thermodynamic voltage and thermo-neutral voltage.

• Journal of Radiation Protection and Research
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• v.38 no.4
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• pp.172-178
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• 2013

In this study, neutron detection efficiency of the UNDA system, which has been developed for study on nuclear material accountancy in a future pyro-process facility, was evaluated by using the MCNPX code. The detection efficiency was evaluated as a function of (1) positions of $^{252}Cf$ neutron source in the axial and radial directions, and (2) thicknesses and locations of the container filled with the depleted uranium materials for two different designs of the UNDA. In the case of $^{252}Cf$ source positions, detection efficiency was distributed from 6.83% to 13.35%. As $^{252}Cf$ source was positioned at upper part in the axial direction, detection efficiency was decreased after a slight increase. On the other hands, as $^{252}Cf$ source was positioned at outer part in the radial direction, detection efficiency was increased. In the case of container thickness, there was a slight decline when the thickness was increased. As the container was located at upper part, detection efficiency was decreased and as the container was located at outer part, detection efficiency was increased. Detection efficiency was varied from 10.31% to 13.61%. These values were higher than that of $^{252}Cf$ source case. The UNDA with polyethylene cover has about 2% higher detection efficiency than the UNDA without the cover.