• Economic and Environmental Geology
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• v.42 no.6
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• pp.609-618
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• 2009

High permeable faults are important geological structures for fluid flow, energy, and solute transport. Therefore, high permeable faults play an important role in the formation of hydrothermal fluid (or hot spring), high heat flow, and hydrothermal ore deposits. We conducted 2-D coupled thermal and hydraulic modeling to examine thermohydraulic behavior in fault zones with various permeabilities and geometric conditions. The results indicate discharge temperature in fault zones increases with increasing fault permeability. In addition, discharge temperature in fault zones is linearly correlated with Peclet number ($R^2=0.98$). If Peclet number is greater than 1, discharge temperature in fault zones can be higher than $32^{\circ}C$. In this case, convection is dominant against conduction for the heat transfer in fault zones.

• Journal of Powder Materials
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• v.19 no.6
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• pp.435-441
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• 2012

A new manufacturing process of Fe-Cr-Al powder porous metal was attempted. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on PU (Polyurethane) foam through the electrospray process. And then degreasing and sintering processes were conduced. In order to examine the effect of sintering temperature in process, pre-samples were sintered for two hours at temperatures of $1350^{\circ}C$, $1400^{\circ}C$, $1450^{\circ}C$, and $1500^{\circ}C$, respectively, in $H_2$ atmospheres. A 24-hour TGA (thermo gravimetric analysis) test was conducted at $1000^{\circ}C$ in a 79% $N_2$+21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing sintering temperature (2.57% oxidation weight gain at $1500^{\circ}C$ sintered specimen). The high temperature oxidation mechanism of newly manufactured Fe-Cr-Al powder porous metal was also discussed.

• Journal of Powder Materials
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• v.21 no.1
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• pp.55-61
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• 2014

Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing and sintering processes were conduced. In order to examine the effect of cell size ($200{\mu}m$, $450{\mu}m$, $500{\mu}m$) in process, pre-samples were sintered for two hours at temperature of $1450^{\circ}C$, in $H_2$ atmospheres. A 24-hour thermo gravimetric analysis test was conducted at $1000^{\circ}C$ in a 79% $N_2$ + 21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing cell size. In the $200{\mu}m$ porous metal with a thinner strut and larger specific surface area, the depletion of the stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared with the 450, $500{\mu}m$ porous metals.

• Tunnel and Underground Space
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• v.17 no.6
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• pp.464-474
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• 2007

An enhancement in the performance and safety of a high-level waste repository requires a validation of its engineered barrier. An engineering-scale test (named "KENTEX") has been conducted to investigate the thermal-hydro-mechanical behaviors in the engineered barrier of the Korean reference disposal system The validation test started on May 31, 2005 and is still under operation. The experimental data obtained allowed a preliminary and qualitative interpretation of the thermal-hydro-mechanical behaviors in the bentonite blocks. The temperature was higher as it became closer to the heater, while it became lower as it was farther away from the heater. The water content had a higher value in the part close to the hydration surface than that in the heater part. The relative humidity data suggested that a hydration of the bentonite blocks might occur by different drying-wetting processes, depending on their position. The total pressure was continuously increased by the evolution of the saturation front in the bentonite blocks and thereby the swelling pressure. Near the heater region, there was also a significant contribution of the thermal expansion of bentonite and the vapor pressure in the pores of the bentonite blocks.

• Korean Journal of Agricultural Science
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• v.42 no.3
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• pp.231-235
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• 2015

This study was performed to investigate the change of the body surface temperature during socialization of weaning pigs. A total of 108 piglets (Landrace 60 and Yorkshire 48) aged 31 (${\pm}1.1$) day was used for this study. Experiment was designed as follows; familiar group (T1), randomly mixed with unfamiliar piglets (T2), mixed based on weight of unfamiliar piglet (T3). The transport and mixing of pigs were performed at 10:00, and then body surface temperature was taken by thermo-graphic camera after 4 hours (14:00). Average surface temperature and hot-spot-temperature, which is the hottest spot of the body surface, were analyzed using Testo IRsoft 3.1 software. Average temperature of body surface were 36.0, 38.2, and 37.5 in T1, T2, and T3, respectively. Average of body surface temperature in T2 and T3 were higher (p<0.001) than T1, and average temperature of body surface of T3 was greater (p<0.001) than that of T2. The hot-spot-temperature of T1, T2, and T3 were 38.7, 39.5, and 39.6, respectively. The hot-spot-temperature of T2 (p<0.01) and T3 (p<0.001) were significantly higher than that of T1. Above results demonstrate that grouping unfamiliar pigs leads to increase in the body temperature possibly by pigs aggressive behavior during social conflict. By the result on average body temperature, this study suggests that the mixing with similar body weight would increase the struggle time and frequency.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.225-234
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• 2011

In this study, an in situ heater test for investigating the thermo-mechanical behavior related to heat flow was carried out. It was the first in situ heater test in Korea. For the test, an adequate design of heater, observation sensors, and data logging system was developed and installed with a consideration of the site condition and the test purposes. It was possible to observe that steep joints are overwhelmingly developed in the test area from a joint survey. The major rock and rock mass properties at the test site could be determined from the thermal and mechanical laboratory tests using the rock cores from the site. From the measured rock temperature distribution, it was possible to observe the influence of the rock joints and the heat flow through tunnel wall. When the heater temperature was maintained as $90^{\circ}C$, the rock temperature at 0.3 m from the heater hole was increased up to $40^{\circ}C$.

• Steel and Composite Structures
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• v.35 no.3
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• pp.439-447
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• 2020

This paper presents two sets of full three-dimensional thermoelastic finite element analyses of superimposed thermo-mechanically loaded Spar Wingskin Joints made with laminated Graphite Fiber Reinforced Plastic composites. The study emphasizes the influence of residual thermal stresses and material anisotropy on the inter-laminar delamination behavior of the joint structure. The delamination has been pre-embedded at the most likely location, i.e., in resin layer between the top and next ply of the fiber reinforced plastic laminated wingskin and near the spar overlap end. Multi-Point Constraint finite elements have been made use of at the vicinity of the delamination fronts. This helps in simulating the growth of the embedded delamination at both ends. The inter-laminar thermoelastic peel and shear stresses responsible for causing delamination damage due to a combined thermal and a static loading have been evaluated. Strain energy release rate components corresponding to the Mode I (opening), Mode II (sliding) and Mode III (tearing) of delamination are determined using the principle of Virtual Crack Closure Technique. These are seen to be different and non-self-similar at the two fronts of the embedded delamination. Residual stresses developed due to the thermoelastic anisotropy of the laminae are found to strongly influence the delamination onset and propagation characteristics, which have been reflected by the asymmetries in the nature of energy release rate plots and their significant variation along the delamination front.

• Fire Science and Engineering
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• v.30 no.1
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• pp.31-36
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• 2016

This study investigates the characteristics of thermal decomposition of an epoxy-based intumescent paint using thermogravimetric analysis (TGA) and numerical simulation. A mathematical and numerical model is introduced to describe mass loss profiles of the epoxy-based intumescent coating induced by the thermal decomposition process. The decomposition scheme covers a range of complexity by employing simplified 4-step sequential reactions to describe the simultaneous thermal decomposition processes. The reaction rates are expressed by the Arrhenius law, and reaction parameters are optimized to fit the degradation behavior seen during thermogravimetric (TG) experiments. The experimental results show a major 2-step degradation under nitrogen and a 3-step degradation in an air environment. The experiment also shows that oxygen takes part in the stabilization of the intumescent coating between 200 and $500^{\circ}C$. The simulation results show that the proposed model effectively predicts the experimental mass loss as a function of time except for temperatures above $800^{\circ}C$, which were intentionally not included in the model. The maximum error in the simulation was less than 3%.

• Journal of Powder Materials
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• v.19 no.4
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• pp.253-258
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• 2012

The characteristics of $Al_2TiO_5$ ceramics were influenced by the additives and the heat treatment that controls the microcrack behavior at grain boundaries. The effect of additives on $Al_2TiO_5$ ceramics were investigated in terms of mechanical properties and thermal expansion at high temperature. The $Al_2TiO_5$ were synthesized at $1500^{\circ}C$, $1550^{\circ}C$ and $1600^{\circ}C$ for 2h by reaction sintering. The formation of $Al_2TiO_5$ phase was increased by additives that enhanced the volume of the microcrack that can lead to low thermal expansion. The mechanical properties of the stabilized $Al_2TiO_5$ ceramics were increased remarkably at $1100^{\circ}C$, $1200^{\circ}C$ and $1300^{\circ}C$ due to the oneset of mechanical healing of grain-bondary microcracks at a high temperature. The amount of microcrack was decreased at lower sintering temperature that causes the increase of mechanical properties at high temperature.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.41-47
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• 2012

It is very important to predict the nonlinear behavior of combustion instability such as transition phenomena and limit cycle amplitude for fully understanding and controlling the instabilities. These nonlinear instability characteristics are highly dependent upon the flames' nonlinear dynamics in a gas turbine premixed combustor. In this study, nonlinear instability TA(Thermo-acoustic) models were introduced by applying the concept of flame describing function to the thermoacoustic analysis method. As a result of model development, for a given combustor length, the growth rate of instability was greatly affected by the change in amplitude, although the instability frequency was not. Further researches under various operating conditions and model validation on limit cycle amplitude are required.