• KIEAE Journal
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• v.14 no.4
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• pp.119-125
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• 2014

This study investigated the effects of pipe network materials and distance on system performance utilizing unused energy sources in large-scale horticulture facility. For this, the modeling was performed with a 100 m long and 100 m wide rectangular shaped glass house having an area of 1ha ($10,000m^2$) using EnergyPlus software. The heat sources considered were air source, geothermal heat, power plant waste heat, sea water heat, and river water. The temperature variation of the fluid with regard to pipe material and distance from the heat source and the resultant heat pump electricity consumptions were calculated. It turned out that the fluid temperature reaching the heat pump increased as the distance from the heat source increased in case of sea water and river water, which have higher temperatures than the surrounding soil, improving the heat pump efficiency. It was vice versa in case of the power plant waste heat. In addition, pipe material of PVC showed the smallest effect on the system performance variation due to the lowest thermal conductivity, compared to PB and HDPE.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.513-514
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• 2006

Recently intradiscal electrothermal therapy is introduced, which is a new and minimally invasive technique fer the treatment of discogenic low back pain. This procedure involves the percutaneous threading of a flexible catheter into the disc under fluoroscopic guidance. The catheter, composed of thermal resistive coil, heats the posterior annulus of the disc, causing contraction of collagen fibers and destruction of afferent nociceptors. This study tries to investigate the effects of the important factors of this procedure such as heat source temperature and heat applying time on the temperature distribution within the intervertebral disc. This study utilized both computer simulation and the experiment for the verification of finite element analysis. FE analysis was carried out with ANSYS v7.0 (ANSYS Inc, USA) using 10,980 number of brick element and 12,551 number of node. The functional spinal units of 5 month old swine were used for the experiment and the temperature was monitored using 10 channel temperature measurement device MV200. Through this study, it was able to analyze the temperature range of inner intervertebral disc by two mechanisms which are known to alleviate pain clinically. The results showed that when the heat source temperature was kept up 80 degree for 1,020 seconds, the temperature of inner annulus reached at 45 degree up to the distance of 15.6mm from heat source, which explains coagulation of inner annulus by heat. When the same heat source was used, the temperature of inner nucleus reached at 60 degree up to the distance of 9mm from heat source, which explains contraction of inner nucleus by heat.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.5
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.

• Laser Solutions
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• v.9 no.1
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• pp.9-16
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• 2006

Glass is one of brittle materials. Generally, brittle material is weak for tensile stress but strong for compression stress. Laser breaking of glass used this brittle characteristics. Laser breaking of glass was simulated to optimize breaking condition by using commercial FEM code MARC which is applicable to thermo-mechanical coupling analysis. Various shapes of heat sources were applied to the analysis and the distance between heating and cooling source were varied for each simulation. The shapes of heat sources were circle, single and double ellipse and the distance was varied from 0mm to 30mm. Moving heat sources were designed on the basis of experimental condition. As a result, double elliptic shape of heat source was the most suitable among them in laser breaking of glass. And it should be useful to determine optimal condition of laser breaking for glass.

• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.56-60
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• 2002

The purpose of this study was to present the thermal characteristics of the working uniform exposed to the radiation heat. The effect of exposure time and exposure distance on the changes and the relationship between physical properties were investigated experimentally. Regardless of the kind of working uniform, the surface temperature of the working uniform with exposed time sharply increases as exposed distance is more close and the reaching time of steady state is shorter. The surface temperature of working uniform exponentially decreases as exposed distance become more distant. For the safety of the working man, it is necessary that he work far away at a fixed standard distance from the radiant heat source.

• Fire Science and Engineering
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• v.17 no.1
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• pp.21-25
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• 2003

This experimental study shows the thermal characteristics of the fire fighter's waterproof clothing exposed to the radiation heat. From the test results, the surface temperature of the fire fighter's waterproof clothing exposed to the radiation with the passage of time sharply increased as the exposed-distance became closer. Also as the radiant heat flux increased, the surface temperature is higher and the time reaching steady state is sharply shorter. As the exposed-distance become more distant, the surface temperature of the fire fighter's waterproof clothing decreased and the difference of temperature between the front side and the back side of the clothing decreased as well. Besides, the radiant heat flux increased, the safety exposed-distance increased. Therefore it is necessary that fire fighter have to work keeping a fixed safe distance from the radiant heat source.

• Geosystem Engineering
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• v.21 no.6
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• pp.309-317
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• 2018

We employ a three-dimensional indirect boundary element method (BEM) to simulate temperature change around an underground liquefied natural gas storage cavern. The indirect BEM (IBEM) uses fictitious heat source strength on boundary elements as basic variables which are solved from equations of boundary conditions and then used to compute the temperature change at other points in the considered problem domain. The IBEM requires evaluation of singular integration for temperature change due to heat conduction from a constant heat source on a planar (triangular) region. The singularity can be eliminated by a semi-analytical integration scheme. However, it is found that the semi-analytical integration scheme yields sharp temperature gradient for points close to vertices of triangle. This affects the accuracy of heat flux, if they are evaluated by finite difference method at these points. This difficulty can be overcome by a combination of using a direct numerical integration for these points and the semi-analytical scheme for other points distance away from the vertices. The IBEM and the hybrid integration scheme have been verified with an analytic solution and then used to the application of the underground storage.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.12
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• pp.986-993
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• 2007

The microchannel heat sink is promising heat dissipation method far high density electronic devices. The cross-sectional shape of MEMS based microchannel heat sink is limited to triangular, trapezoidal, and rectangular due to their fabrication method. And heat is added to one side surface of heat source. Therefore, those specific conditions make some complexity of heat transfer in microchannel heat sink. Though many previous research of conjugate heat transfer in microchannel was conducted, most of them did not consider heat loss. In this study, numerical investigation of conjugate heat transfer in rectangular microchannel was conducted. The method of heat loss evaluation was verified numerically. Heat distribution was different for each wall of rectangular microchannel due to thermal conductivity and distance from heat source. However, the ratio of heat from each channel wall was correlated. Therefore, the effective area correction factor could be proposed to evaluate accurate heat flux in one side heating condition.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.4
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• pp.14-21
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• 2015

Korean government plans to establish large-scale horticulture facility complexes using reclaimed land in order to improve the national competitiveness of agriculture at the government level. One of the most significant problems arising from the establishment of those large-scale horticulture facilities is that these facilities still largely depend on a fossil fuel and they require 24 h a day heating during the winter season in order to provide the necessary breeding conditions for greenhouse crops. These facilities show large energy consumption due to the use of coverings with large heat transmission coefficients such as vinyl and glass during heating in the winter season. This study investigated the applicability of waste heat from power plant for large-scale horticulture facilities by evaluating the waste heat water temperature, heat loss and energy saving performance as a function of distance between power plant and greenhouse. As a result, utilizing power plant waste heat can reduce the energy consumption by around 85% compared to the conventional gas boiler, regardless of the distance between power plant and greenhouse.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.18-25
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• 2016

The incandescent lamp is an electric light fixture with a tungsten filament heated to a high temperature, by passing an electric current through it, until it glows with visible light. The hot filament is protected from oxidation with a glass bulb that is filled with inert gas. The incandescent lamp has fire risk when combustible materials are close to its glass bulb. Because its lamp has the property which converts 90~95 percents of the electric power to heat energy. 2015 national fire statistics show that fires caused by lighting fixtures were 652 cases, and incandescent lamps(44 cases) and halogen lamps(53 cases) accounted for 15 percents in those of high heating light fixtures. Since incandescent lamp fires account for about 45 percents in the high heating light fixture, we could not overlook the fire risks by the incandescent lamp. Although many studies related with those have been conducted, incandescent lamp fires are continuously occurred. This study was carried out to study the fire risk of ignition of wood due to radiant heat of incandescent lamp. Radiant heat flux of the incandescent lamp was predicted by applying point source model, and critical distance for ignition of wood was calculated by applying integral model. The results from this study could applied to fire prevention activities related to light bulb, and it could be used in fire cause investigations related to radiant heat of incandescent lamp.