• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.173-182
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• 2005

The Performance of U-tube ground heat exchanger for geothermal heat Pump systems depends on the thermal properties of the soil, as well as grout or backfill materials in the borehole. In-situ tests provide a means of estimating some of these properties. In this study, in-situ thermal response tests were completed on two vertical boreholes, 130 m deep with 62 mm diameter high density polyethylene U-tubes. The tests were conducted by adding a monitored amount of heat to water over a $17\~18$ hour period for each vertical boreholes. By monitoring the water temperatures entering and exiting the loop and heat load, overall thermal conductivity values of grout/soil formation were determined. Two parameter estimation models for evaluation of thermal response test data were compared when applied on the same temperature response data. One model is based on line-source theory and the other is a numerical one-dimensional finite difference model. The average thermal conductivity deviation between measured data and these models is of the magnitude $1\%$ to $5\%$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1651-1656
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• 2017

This paper deals with the thermal and mechanical properties of ceramic coating material for bus bars. A ceramic coated samples were prepared for the mechanical properties test. There are two types of samples. One is a square shape and the other is a busbar shape. Each sample was deteriorated for 30 days to compare the thermal and mechanical properties with the non-degraded samples. Two thermal properties tests are TGA and flammability tests, and four mechanical properties tests are drop impact test, cross cut, tensile test, and bend test. The ceramic coating material was never damaged by impact and did not separate from aluminum in the cross cut test. In the tensile test, the breakage of the insulating material did not occur until aluminum fractured, and the breakage of the insulating material did not occur until the maximum load in the bending test. The decomposition temperature (melting point) of the ceramic coating material was higher than that of other epoxy insulators. This ceramic coating material is nonflammable and it has excellent fire stability.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.546-547
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• 2012

In the three-phase power system using the three-phase load, when any one-phase is open-phase, the unbalanced current flows and the single-phase power supplied by power supply produces over-current. As a result, the enormous damage and electrical fire can be given to the power system. In order to improve these problems, this paper is proposed a new control circuit topology for open-phase protection using semiconductor devices. Therefore, the proposed open-phase protection device (OPPD) enhances the sensing speed and precision, and has the advantage of simple fitting in the three-phase distribution panel in the field, as it manufactures into small size and light weight. As a result, the proposed OPPD minimizes the electrical fire from open-phase, and contributes for the stable driving of the power system.

• Korean Journal of Construction Engineering and Management
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• v.15 no.5
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• pp.13-21
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• 2014

This study on condominium complex will adopt the quantitative assessment of the influence on the environment throughout the entire life cycle of buildings. This paper applies input-out analysis in order to analyse embodied energy regarding input of materials at material production phase. Also, it calculates environment load at use and demolition and destruction Phases of buildings as analysing energy consumption. The study categorises environment load as six impact categories and undertakes environmental impact evaluation. The consequence shows that the environment load of multi-unit dwelling takes up 88.2% out of the entire environment load of condominium complex. Also, as a result of analyzing the environmental impact of the life cycle of condominium buildings, it was found that such environmental impact comprised of about 11.96% of all industries in Korea that had an environmental impact.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.6 no.2
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• pp.1-7
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• 2010

The objective of this study is to find the optimal control algorithm of a hybrid Plant, which is combined by renewable energy plant of the GSHP(Geothermal Source Heat Pump) and the normal plant (Chiller, boiler). The work presented in this study was carried out in the EnergyPlus(Version 2.0). The EnergyPlus was modified in order to simulate the hybrid plant. The plant system was controlled by the load-range-based operation in which schemes select a user specified set of equipment for each user specified range of a particular simulation condition. In the use of the load-range-based operation, four kind of control cases were defined and simulated in order to obtain the optimal control algorithm of the hybrid plant. The result showed that the Case 2 was the optimal control algorithm which used the GSHP as a base operating plant and the normal plant as an assistant operating plant. Even though the normal plant was operated in full load and the renewable energy plant of the GSHP was operated in partial load, the annual energy consumption of the normal plant was larger than that of the GSHP plant.

• Korean Journal of Environmental Agriculture
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• v.42 no.3
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• pp.239-252
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• 2023

Most apple trees in South Korea are grafted on M.9 and M.26 rootstocks; however, these rootstocks are susceptible to fire blight. Although M.7 rootstocks are moderately resistant to fire blight, they tend to exhibit excessive vigor, which is unsuitable for high-density planting, unless weak cultivars are used. This study investigated the vegetative growth, yield, and fruit quality of apple trees grafted onto M.7, M.9, or M.26 rootstocks to assess the feasibility of establishing high-density apple orchards domestically using the M.7 rootstock a period of seven years (1-7 years after planting). Rootstocks were tested using three cultivars with contrasting induced vigor and harvesting times: vigorous and late-maturing 'Fuji,' moderate vigor and middle-maturing 'Hongro,' and low vigor and early-maturing 'Sansa.' The planting density was maintained constant, with 190 trees per 10 a. Primary thinning (leaving only the king fruit on clusters) was performed, whereas secondary thinning (controlling crop load) was not. Vegetative growth, accumulated yield per 10 a, and yield efficiency varied depending on cultivars and rootstocks; however, the cultivars had a more notable effect on fruit quality than the rootstocks. Biennial bearing often occurred in the M.26 rootstock. 'Fuji'/M.7 was overly vigorous for high-density planting. The fruit quality and accumulated yield per 10 a of M.7 were similar to those of M.9 with the 'Hongro' and 'Sansa' cultivars. In particular, 'Hongro'/M.7 did not show tree vigor reduction due to heavy crop load, and the degree of biennial bearing in 'Sansa'/M.7 was not particularly high. These results indicated that high-density apple planting using the M.7 rootstock was achievable using the 'Hongro' and 'Sansa' cultivars.

• Geomechanics and Engineering
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• v.14 no.6
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• pp.581-588
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• 2018

In order to explore the comprehensive evaluation means of the extent of hydraulic fracturing region in coal seams, we analyzed the feasibility of detecting the response of coal rock direct current (DC) apparent resistivity to hydraulic-fracturing using Archie's theory, and conducted experimental researches on the response of DC resistivity in the hydraulic fracturing process using small-scale coal rock samples. The results show that porosity and water saturation are the two factors affecting the apparent resistivity of coal rock while hydraulic fracturing. Water has a dominant effect on the apparent resistivity of coal rock samples. The apparent resistivity in the area where water flows through is reduced more than 50%, which can be considered as a core affect region of hydraulic fracturing. Stress indirectly impacts the apparent resistivity by changing porosity. Before hydraulic fracturing, the greater axial load applied, the more serious the rupture in the samples, resulting in the greater apparent resistivity. Apparent resistivity testing is a potential regional method to evaluate the influence range of hydraulic fracturing in coal seams.

• Journal of the Korean Society of Safety
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• v.30 no.5
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• pp.8-13
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• 2015

Molded Case Circuit Breakers (MCCBs) are typically used to provide over current protection for electrical safety caused by short circuit faults and overloads in indoor low voltage power systems. The MCCB automatically connects and disconnects loads from the electrical source when the current reaches a value and duration that will cause an excessive. However, the MCCB sometimes is not interrupted due to a malfunction, nuisance tripping, or in a fire. Ensuring electrical safety is very important in a indoor low voltage power system. This paper presents the operating characteristics of MCCBs according to a temperature rise from room temperature to 160 degrees Celsius delivered by a radiant panel heater. The ABS 54c(rated current: 30A) of the hydraulic magnetic trip type was used in the experiments. The signals of temperature, voltage, and current were measured using the high accuracy Signal Conditioning Extensions for Instrumentation (SCXI) measurement system with the LabVIEW program manufactured by National Instruments. The operating characteristics were measured as functions of current amplitude and ramp-up rate. The MCCB tripping time decreased as a result of increasing current amplitude and ramp-up rate under a temperature rise condition, because the temperature and level of the current are directly proportional to the tripping time. Additionally, an instantaneous operation was observed after 8 times of the rated current, and the MCCB began to melt a surface temperature of around 300 degrees Celsius of. The experimental results coincided well with the operating curve.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.7-12
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• 2008

An experimental study has been conducted to investigate the effect of tunnel slope on critical velocity by using the model funnel of the 1/20 reduced-scale applying the Floods scaling law. the square liquid pool burners were used for methanol, acetone and n-heptane fires. tunnel. Tunnel slopes varied as five different degrees $0^{\circ}$, $2^{\circ}$, $4^{\circ}$, $6^{\circ}$ and $8^{\circ}$. The mass loss rate and the temperatures are measured by a load celt and K-type thermocouples for tunnel slope. Present study results in bigger the critical velocity than the research of Atikinson and Wu using the propane burner. Therefore, when estimating the critical velocity in slope tunnel, the variations of the heat release rate is an important factor. The reason is the ventilation velocity directly affects variation of heat release rate when slope tunnel fire occurred.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.184-188
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• 2008

Performance degradation of concrete structures is generally caused by structural deteriorations, such as cracks. It may result in serious defects of concrete structures. Methods of damage detection are used a visual angle of human or non-destructive test, and they are using various sensors. Problems of crack damage detection are occurred to directions of cracks by using 1 axial type of accelerometer in concrete element. In addition, these sensors are not used to occurring fire in RC building. Thermocouple sensors are able to using measurement of temperature in fire, and then deformations of main element and structures are not used. In this study, fundamental studies for development of multiple function sensor using 3 axial type of accelerometer and electric resistance property of thermocouple sensors are discussed estimation to stability of structures when happened form active load or fire, and so on.