• KIEAE Journal
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• 제13권4호
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• pp.49-54
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• 2013

released by IEA, 2010, indicated that Korea's GDP, of 8 countries surveyed-Korea, Frans, Germany, Italy, Japan, the UK, the USA, and Australia-was the lowest, but the electric consumption per head was third, following America and Australia. Thus, our government has been striving to reduce energy usage and especially to lessen the energy used in buildings, proposing a variety of road maps such as 'building energy efficiency rating' and 'energy saving design standards of buildings'. Accordingly, this study investigated the effect of the items of machine part among EPI items on the energy saving rate. I measured energy usage by ECO2 program, for simulation program, that is used for the building energy efficiency rating. Result showed that items concerning control of pumps and fans had much more saving rate than the ones concerning efficiency of heater and cooler that had bigger scores assigned among EPI items. Result showed that items concerning control of pumps and fans had much more saving rate than the ones concerning efficiency of heater and cooler that had bigger scores assigned among EPI items. Therefore, I think that grades assigned to items in energy performance index need to be corrected.

• Journal of the Korean Solar Energy Society
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• 제27권4호
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• pp.121-128
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• 2007

Convective heat loss from solar tower receiver is experimentally investigated in wind tunnel with tilt angles and operating conditions. In order to simulate the receiver, an electric heater, which is made of aluminum (width : 100 mm, height : 100mm) is used and installed in the wind tunnel. The convective heat loss from the receiver is dependent on the direction and the velocity of the wind and the surface temperature of the receiver. The tilt angle and surface temperature of the receiver are varied from 0o (cavity facing straight down) and 90o(cavity aligned horizontally) and from $150^{\circ}C$ to $250^{\circ}C$, respectively. Also, the wind speed is changed from 0 to 4m/s. The convective heat loss is obtained by measuring consumed power to the heater to maintain the desired surface temperature. It is concluded that Nusselt number increases with increasing wind speed for all cases. Especially, it is showed that Nusselt number can be maximized when the tilt angle is 30o.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.290-293
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• 2017

A direct-connected, continuous type combustion test facility was developed to test a supersonic combustor model used in scramjet engines. The facility requirements were determined by assuming the flight speed of Mach 5, yielding the combustor inlet flow speed of Mach 2. Also the cross-section of the supersonic combustor under test was assumed as $32mm{\times}70mm$. As a result, the facility was designed to have the flow total pressure of 548 kPaA, total temperature of 1,320 K, and flow rate of 0.776 kg/s. The facility consists of a turbo type air compressor, electric air heater, vitiation air heater and a two dimensional facility nozzle to accelerate the flow to Mach 2. Also, an oxygen supply system was added to compensate the vitiation. The exhaust de-pressurization system is not added. Designed pressure, temperature, and flow rate were verified through the test operation of the facility.

• Journal of Biosystems Engineering
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• 제43권4호
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• pp.342-351
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• 2018

Purpose: Recently, an increasing number of farms have been cultivating shiitake mushrooms using a sawdust substrate and a cooler/heater. In this study, an attempt was made to develop an environmental control system using a heat pump for cultivating high-quality shiitake mushrooms. Methods: An environmental control system, consisting of an air-to-water type heat pump, a thermal storage tank, and a radiator in a variable opening chamber, was designed and fabricated. The system was also installed in the cultivation facility of a farm cultivating shiitake mushrooms so as to compare the proposed control system with a conventional environmental control system using a cooler-condensing unit and an electric hot water boiler. Results: The uniformity of the environment was analyzed through environment measurements taken at several positions inside the cultivation facility. It was determined that the developed environmental control system is able to control the variations in temperature and relative humidity to within 1% and 3%, respectively. In addition, a maximum temperature difference of $30^{\circ}C$ (maximum of $35^{\circ}C$, minimum of $5^{\circ}C$) and a maximum relative humidity difference of 30% (maximum of 90%, minimum of 60%) can be attained within 30 min inside the cultivation facility through the cooling of the heat pump and heating of the radiator in a variable opening chamber. Thus, the developed control system can be used to cultivate high-quality shiitake mushrooms more effectively than a conventional cooler and heater. Conclusions: In comparison with a conventional environmental control system, the developed system decreased the yield of ordinary mushrooms by 65%, and increased that of high-quality mushrooms by 217%. This corresponds to a 16% increase in gross farm income. Consequently, the developed system is expected to improve the income of shiitake mushroom cultivating farms.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제36권4호
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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.

• Journal of the Korean Society for Railway
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• 제11권2호
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• pp.151-157
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• 2008

The DPF temperature distribution which has a great effect on regenerating the ceramic filter effectively was measured at 30 locations using K-type thermocouples. Five partitioned electric heaters were used for heating the ceramic filter and they are switched ON/OFF in order. Also, the temperature distribution in the ceramic filter was measured with varying the electrical power supply to the heaters and the mass flow rate of the air supply from a blower. The uniform distribution of the air flow velocity at the inlet of the DPF make that of the temperature in the ceramic filter. The difference in heating ability between the partitioned heaters had a great effect on the temperature distribution in the ceramic filter.

• Journal of Satellite, Information and Communications
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• 제11권3호
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• pp.24-27
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• 2016

In this study, a 1kW Solid Oxide Fuel Cell(SOFC) test system was developed. A SOFC is the most promising power system to provide the higher efficient(over 50%) for house application area(1~10kW). To develop the optimized test system, the temperature control module that controls the preprocess and reaction condition, the flow control module that controls of the mass of reactants, and the electric loader that tests the discharge performance condition, etc. The temperature control module was designed to provide the high control resolution(under $1^{\circ}C$ at $750^{\circ}C$ of operating temperature) using K-type thermal couple. The flow control module was designed control blower and heater precisely using the phase control method. And the electric loader is designed that provide CV, CC, CR discharge mode and minimized the operating error adopting the independent DC-DC converter on analog input and output module. The performance of the developed SOFC test system showed that the accuracy of stack voltage was 0.15% at 80V and stack current was 0.1% at 100A.

• Journal of Digital Convergence
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• 제19권6호
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• pp.143-162
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• 2021

Research on consumers' perception and willingness to purchase Battery Electric Vehicles (BEVs) is necessary to simulate BEVs' deployment in South Korea because South Korea's BEVs market is still in the early stage. This paper derives a theoretical framework for consumer segmentation based on consumers' willingness to purchase before and after BEV usage experience. In particular, this study empirically evaluates consumers' willingness to purchase and concerns using the survey data from BEVs users in either Seoul or the Jeju region. The empirical results from logit models show that experienced consumers' concerns about the heater and air conditioning (HAC) in BEVs decreased the consumers' willingness to buy, while greater daily driving distances increased the consumers' willingness to buy. In addition, the empirical findings from ordered probit models show that experienced consumers' concerns about the short driving distance, the availability of maintenance service (i.e., A/S service) during unexpected events, and the difficulties of driving BEVs up-hill increased the degree of concern about HAC. This paper will provide insights related to consumer segmentation, R&D, marketing strategies, and policy design for policymakers and firms.

• Journal of the Korean Society of Safety
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• 제38권4호
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• pp.8-14
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• 2023

This study presents the characteristics of short circuits (SCs) caused by excessive currents in high-voltage cables used in electric vehicles and emphasizes the need to calculate the cross-sectional areas of these cables according to the SC current. Three direct current power supplies were connected in parallel to test the SC characteristics caused by excessive currents, and a timer and a magnetic contactor were used to deliver the conduction time and SC current. A circular infrared-radiation heater was used to test the temperature-dependent SC characteristics, a thermocouple was used to measure the temperature, and a shunt resistor was used to measure the current. As the SC current increased, the fusing time of the cable decreased. Additionally, a high-voltage cable (with an area of 16 mm² ) used in electric vehicles fused when a current (approximately equal to 55 times the allowable current) flowed for 0.2 s (operating time of the protective device). When the SC current is 10 kA, the cable may fuse during the operating time of the protective device, thus creating a fire hazard. In electric vehicles, the size of the SC current increases in proportion to the capacity of the battery. Thus, the cross-sectional areas of the cables used should be calculated accordingly, and cable operations should be properly coordinated with the surrounding protective devices.

• International Journal of Highway Engineering
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• 제15권2호
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• pp.19-27
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• 2013

PURPOSES : This study aims to investigate the snow-melt effects of an underground electric heater's snow-melt system via a field performance test, for evaluating the suitability of the system for use on a concrete pavement. The study also investigates the effectiveness of dynamic measures for clearing snow after snowfall events. METHODS : In order to check the field applicability, in November 2010, specimens were prepared from materials used for constructing concrete pavements, and underground electric heating meshes (HOT-mesh) were buried at depths of 50 mm and 100 mm at the site of the Incheon International Airport Construction Research Institute. Further, an automatic heating control system, including a motion sensor and pavement-temperature-controlled sensor, were installed at the site; the former sensor was intended for determining snow-melt effects of the heating control system for different snowfall intensities. Pavement snow-melt effects on snowy days from December 2010 to January 2011 were examined by managing the electric heating meshes and the heating control system. In addition, data on pavement temperature changes resulting from the use of the heating meshes and heating control system and on the dependence of the correlation between the outdoor air temperature and the time taken for the required temperature rise on the depth of the heating meshes were collected and analyzed. RESULTS : The effects of the heating control system's preheat temperature and the hot meshes buried at depths of 50 mm and 100 mm on the melting of snow for snowfalls of different intensities have been verified. From the study of the time taken for the specimen's surface temperature to increase from the preheat temperature ($0^{\circ}C$) to the reference temperature ($5{\sim}8^{\circ}C$) for different snowfall intensities, the correlation between the burial depth and outdoor air temperature has been determined to be as follows: Time=15.10+1.141Depth-6.465Temp CONCLUSIONS : The following measures are suggested. For the effective use of the electric heating mesh, it should be located under a slab it may be put to practical use by positioning it under a slab. From the management aspect, the heating control system should be adjusted according to weather conditions, that is, the snowfall intensity.