• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.140-146
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• 2005

The on-line optimal control algorithm for central heating system has been researched for minimizing energy consumption while maintaining the comfort of indoor thermal environment in terms of the environmental variables such as indoor heating load and outdoor temperature variation. This study has been done by using TRNSYS Program in order to analyze the central heating system. The optimal control algorithm shows good energy Performances in comparison with the conventional one.

• Journal of the Korean Solar Energy Society
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• v.34 no.3
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• pp.122-132
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• 2014

Sustainability became the keyword of our society worldwide, and it is undoubtful that buildings are mainly responsible for green house gas emission and energy consumption. Among different project types, educational facility was selected in this study to find out what needs to be addressed in order to provide students better learning environments. Scorecards from 32 LEED certified school projects went through analysis and essential components as design strategies in sustainable educational facilities were extracted based on application rate of each credit in LEED for School(2009). The extracted data were further analyzed in comparison with related components in G-SEED. The results would be used as guidelines for those of who design sustainable education facilities and prepare green building certifications. and it would further foster architect's responsibility towards green society in Korea.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.11
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• pp.559-569
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• 2017

Various studies examining how to conserve building energy have been conducted recently. From such studies it has been determined that insulation performance of an aircap is viable and therefore aircaps are used as material for improving insulation performance of windows. However, the aircap for improving insulation performance of a window is attached on the front, causing infringement of the prospect right. Therefore, the purpose of this study is to develop an aircap module attached to the window through rolling, conducting performance verification throughfull-scale testbed and verifying its effectiveness. Findings of this study are as follow : 1) The module suggested in this study enables setting of an area wherein the aircap is attached through rolling so that the aircap rolls up using Velcro tape, and an insulation bar is suggested to block the gap between the aircap and window glass. 2) When the aircap is applied to the window, consumption of lighting energy increased during summer and winter by 2.8%~16.4% and 0%~76.2% respectively in comparison to no aircap application, indicating that it is unsuitable for conserving lighting energy. 3) In terms of conserving cooling and heating energy, an advantageous or effective aircap attachment method is the method whereby an aircap is attached to the front surface of a window. However, the method whereby an aircap is attached to a part of a window and where no aircap is attached increases consumption of cooling and heating energy during summer and winter by 6.0%~35.7% and 2.7%~41.6% respectively in comparison to the method wherein an aircap is attached to the front surface of a window. 4) In consideration of conserving cooling, heating and lighting energy, the attachment of an aircap to the front surface of window is the most appropriate method, and it is appropriate to attach the aircap at a position that is 1,500 mm or higher from the floor to secure the prospect right and minimize energy loss.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.10
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• pp.718-723
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• 2012

The purpose of this study is to propose modeling method of Underfloor Air Distribution System with reliability and validity by comparing characteristics of modeling methods. For this, the modeling methods of UFAD were selected by investigating various modeling methods of previous researches. Then, simulations were conducted by using EnergyPlus which is dynamic analysis program of building energy. Annual energy consumption for each method was compared with a wide range of indoor thermal loads. As a result, the methodology of reducing internal gains can cause under sizing of the system. It suggests modeling methods to reflect occupied zone air-conditioning, temperature stratification and supply plenum which are the main characteristics of UFAD.

• Communications for Statistical Applications and Methods
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• v.22 no.6
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• pp.675-683
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• 2015

In the 21st century, we now face the serious problems of the enormous consumption of the energy resources. Depending on the power consumption increases, both China and South Korea face a reduction in available resources. This paper considers the regression models and time-series models to compare the performance of the forecasting accuracy based on Mean Absolute Percentage Error (MAPE) in order to forecast the electricity demand accurately on the short-term period (68 months) data in Northeast China and find the relationship with Korea. Among the models the support vector regression (SVR) model shows superior performance than time-series models for the short-term period data and the time-series models show similar results with the SVR model when we use long-term period data.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.4
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• pp.201-207
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• 2012

Currently, NAND Flash memory has been widely used in consumer storage devices due to its non-volatility, stability, economical feasibility, low power usage, durability, and high density. However, a high capacity of NAND flash memory causes the high power consumption and the low performance. In the convention memory research, a hierarchical filter mechanism can archive an effective performance improvement in terms of the power consumption. In order to attain the best filter structure for NAND flash memory, we selected a direct-mapped filter, a victim filter, a fully associative filter and a 4-way set associative filter for comparison in the performance analysis. According to the results of the simulation, the fully associative filter buffer with a 128byte fetching size can obtain the bet performance compared to another filter structures, and it can reduce the energy*delay product(EDP) by about 93% compared to the conventional NAND Flash memory.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.113-120
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• 2014

To ventilate indoor spaces, axial single-blade fans are widely used in various areas, such as schools, houses, offices, and restaurants. Recently, axial single-blade fans were developed to realize energy efficiency and noise reduction improvements. Here, an experimental study of the air flow characteristics of an axial dual-blade fan is conducted. The characteristics of the axial dual-blade fan were tested via an air flow analysis and with prototypes. For the performance of the fan, the flow rate, power consumption, and noise were evaluated. The result showed that the axial dual-blade fan uses less power and produces less noise in comparison with an axial single-blade fan.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.43-48
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• 2008

The exhaust emissions of diesel engine are recognized as a major cause influencing environment strongly. In this study, the possibility of biodiesel fuel and oxygenated fuel(dimethoxy methane; DMM) was investigated as an alternative fuel for a naturally aspirated direct injection diesel engine. The smoke emission of blending fuel(biodiesel fuel 90vol-%+DMM 10vol-%) was reduced approximately 70% at 2500rpm, full load, in comparison with the diesel fuel. But, power, torque and brake specific energy consumption showed no significant differences. But, NOx emission of biodiesel fuel and DMM blended fuel increased compared with commercial diesel fuel due to the oxygen component in the fuel. It was needed a NOx reduction counterplan that EGR method was used as a countermeasure for NOx reduction. It was found that simultaneous reduction of smoke and NOx emission was achieved with BDF(95 vol-%) and DMM(5 vol-%) blended fuel and cooled EGR method(15%).

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1543-1546
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• 2002

The expandable 4 bit adder/subtracter IC was designed using the adiabatic and dynamic CMOS logic (ADCL) circuit as the ultra-low power consumption basic logic circuit and the IC was fabricated using a standard 1.2 ${\mu}$ CMOS process. As the result the steady operation of 4 bit addition and subtraction has been confirmed even if the frequency of the sinusoidal supply voltage is higher than 10MHz. Additionally, by the simulation, at the frequency of 10MHz, energy consumption per operation is obtained as 93.67pJ (ar addition and as 118.67pJ for subtraction, respectively. Each energy is about 1110 in comparison with the case in which the conventional CMOS logic circuit is used. A simple and low power oscillation circuit is also proposed as the power supply circuit f3r the ADCL circuit. The oscillator operates with a less one volt of DC supply voltage and around one milli-watts power dissipation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.775-780
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• 2008

A dynamic model to simulate LNG reliquefaction process has been developed. The model was applied to two candidate cycles for LNG reliquefaction process, which are Reverse Brayton and Claude cycles. The simulation was intended to simulate the pilot plant under construction for operation of the two cycles and evaluate their feasibility. According to the simulation results, both satisfy control requirements for safe operation of brazed aluminum plate-fin type heat exchangers. In view of energy consumption, the Reverse Brayton cycle is more efficient than the Claude cycle. The latter has an expansion valve in addition to the common facilities sharing with the Reverse Brayton cycle. The expansion valve is a main cause to the efficiency loss. It generates a significant amount of entropy associated with its throttling and increases circulation flow rates of the refrigerant and power consumption caused by its leaking resulting in lowered pressure ratio. It is concluded that the Reverse Brayton cycle is more efficient and simpler in control and construction than the Claude cycle.