• Transactions of Materials Processing
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• v.14 no.7 s.79
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• pp.607-612
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• 2005

In this paper, warm deep drawing process with local heating and cooling technique was attempted to improve the formability of AZ31 magnesium alloy which is impossibly to form by conventional methods at room temperature by finite element method and experiment. For FE analysis, in first model with considering heat transfer, both die and blankholder were heated to 573K while the punch was kept at room temperature by cooling water. Also distribution of thickness and von Mises stress at room temperature and 498k for warm deep drawing were compared by FEM. Uniaxial tension tests at elevated temperature were done in order to obtain the temperature dependence of material constant under temperature of $293K\~573K$ and cross head velocity of $5\~500mm/min$. The phenomenological model for warm deep drawing process in this work was based on the hardening law and power law strain rate dependency. Deep drawing experiment were conducted at temperatures of room temperature, 373K, 423K, 473K, 498K, 523K, and 573K for the blank and deep drawing tools(holder and die) and at a punch speed of 10mm/min.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.3
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• pp.31-38
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• 1991

Effect of thermal cycling on shape memory effect and stabilization of austenite was investigated in Fe-21%Mn alloy. The thermal cyclic treatment was carried out with two types, room temperature${\leftrightarrow}215^{\circ}C$ and room temperature${\leftrightarrow}260^{\circ}C$. In case of the room temperature${\leftrightarrow}215^{\circ}C$, the SME was rapidly increased up to 3 cycles and maintained nearly constant value regardless of further cycles. In case of the room temperature${\leftrightarrow}260^{\circ}C$, however, the SME was increased with increasing the thermal cycle up to 5 cycles and decreased gradually with further cycle. The variation of the ${\varepsilon}$ martensite volume pet with the thermal cycle was in good agreement with the variation of the SME. Therefore, the change of the SME due to the cyclic treatment was explained with the change of the ${\varepsilon}$ martensite content. As the thermal cycle was increased, the $M_s$ temperature was decreased, and the $A_s$ and $A_f$ temperatures were increased, respectively.

• Solar Energy
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• v.15 no.2
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• pp.13-24
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• 1995

Korean traditional Ondol with the sensible heat storage medium has been for a long time used as residential heating system, in these days the concrete Ondol without the heat storage medium was realized as the heating system in the private houses and the apartments. This floor heating system is good for our health. But the concrete Ondol is not desirable for the energy saving and for the maintenance of comfortable room temperature because the heat storage medium is not employed in the concrete Ondol. And as the hot water circulating pipes are buried under the concrete floor, the concrete Ondol system has some kind of problems to be improved. Therefore the new type of Ondol system was developed in this study. And the new Ondol was consisted of latent heat storage material as heat storage medium with a great heat capacity and bioceramics as medium to maintain comfortable room temperature. In this study, the heat transfer characteristics of latent heat storage-bioceramic Ondol was analyzed theoretically.

• Progress in Superconductivity and Cryogenics
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• v.14 no.2
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• pp.32-35
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• 2012

The objective of the present work is to develop a precise instrument for measuring the thermal property of insulating material over a temperature range from 30 K to near room temperature by utilizing a cryocooler. The instrument consists of two thermal links, a test sample, heat sink, heat source and vacuum vessel. The cold head of the cryocooler as a heat sink is thermally anchored to the thermal link and used to bring the apparatus to a desired temperature in a vacuum chamber. An electric heater as a heat source is placed in the middle of test sample for generating uniform heat flux. The entire apparatus is covered by thermal shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. For a supplied heat flux the temperature distribution in the insulating material is measured in steady and transient state. The thermal conductivity of insulating material is measured from temperature difference for a given heat flux. In addition, the specific heat of insulating material is obtained by solving one-dimensional heat diffusion equation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.610-616
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• 2020

This study conducted joint research with the Navy logistics command ship technology research institute to resolve the occurrence of naval vessel's high-temperature warning and equipment shutdown caused by VRTU overheating during summer operation and the dispatch of troops to equatorial regions. The cooling effect was checked according to the installation of a thermoelectric device cooling system, and heat flow and heat transfer characteristics inside VRTU was analyzed using Computational Fluid Dynamics. In addition, the temperature distribution inside the engine room was assessed through interpretation, and the optimal installation location to prevent VRTU overheating was identified. As a result, the average volume temperature inside the VRTU decreased by approximately 10 ℃ with the installation of the cooling system, and the fan installed in the cooling system made the heat circulation smooth, enhancing the cooling effect. The inside of the engine room showed a high-temperature distribution at the top of the engine room, and the end of the HVAC duct diffuser showed the lowest temperature distribution.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.16-22
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• 2024

The conventional degreasing process involves removing oil and contaminants at temperatures above 80℃, resulting in excessive energy consumption, increased process costs, and environmental issues. In this study, we aimed to find the optimal degreasing conditions for the pre-treatment process of electro-galvanizing cold-rolled steel sheets, conducted efficiently at room temperature without the need for a separate heating device. To achieve this, we developed a room temperature degreasing solution and a brush-type degreasing tool, aiming to reduce energy consumption and normalize the decrease in degreasing efficiency caused by temperature reduction. Alkaline degreasing solution were prepared using KOH, SiO₂, NaOH, Na₂CO₃, and Sodium Lauryl Sulfate, with KOH and NaOH as the main components. To enhance the degreasing performance at room temperature, we manufactured additives including sodium oleate, sodium stearate, sodium palmitate, sodium lauryl sulfate, ammonium lauryl sulfate, silicone emulsion, and EDTA-Na. Room temperature additives were added to the alkaline degreasing solution in quantities ranging from 0.1 to 20 wt.%, and the uniformity of degreasing and the adhesion of the galvanized layer were evaluated through Dyne Test, T-bending Test, OM, SEM, and EDS analyses. The results indicated that the optimal degreasing solution composition consisted of NaOH (30 g/L), Na₂CO₃ (30 g/L), SLS (6 g/L), and room temperature additives (≤1 wt%).

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.189-194
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• 2009

In a gas engine based cogeneration system, heat is recovered from two parts, which are jacket water and exhaust gas. The heat from the jacket water is often recovered by a plate type heat exchanger and used for the room heating and/or hot water supply. Depending on the operating conditions of engine and heat recovery system, there should be imbalance in the flow rate and supply pressure between engine and heat recovery side of the heat exchanger. The imbalance cause the deformation of the plate, which affects the pressure drop characteristics. In the present study, the pressure drop inside the heat exchanger has been investigated in a 1/5 scaled test rig and compare with the experimental correlations, which are used for the design.

• Journal of Drive and Control
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• v.16 no.1
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• pp.55-58
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• 2019

• Fire Science and Engineering
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• v.31 no.5
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• pp.19-27
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• 2017

The effects of changes in area and location of fire source, fire growth rate, and volume of compartment on the major fire characteristics, including heat release rate, in closed compartment fires were examined. To this end, a fire simulation using Fire Dynamics Simulator (FDS) was performed for ISO 9705 room with a closed opening. As main result, it was found that the changes in the area and location of fire source did not significantly affect the thermal and chemical characteristics inside the compartment, such as maximum heat release rate, total heat release, maximum temperature at upper layeras well as species concentrations. However, increasinthe fire growth rate and volume of compartment resulted in increase of the maximum heat release rate and total heat release, decrease in the limiting oxygen concentration and increase in the maximum CO concentration. Finally, a methodology for the application of fire growth curves to closed compartment fires was proposed by deriving the correlation of the maximum heat release rate expressed as a function of the fire growth rate and the volume ratio of compartment based on the ISO 9705 room.

• Food Science and Biotechnology
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• v.17 no.3
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• pp.603-607
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• 2008

Thirteen commercial antimicrobial products were examined to assess the sporicidal activity against Bacillus cereus spores at room temperature, 60 and $85^{\circ}C$. Neither the antimicrobials showed detectable antimicrobial activity against the B. cereus spores nor induced spore germination after the treatment at 0.5 or 1.0%(w/v, v/v) commercial antimicrobial agents at room temperature for 0.5 to 4 hr. However, when the antimicrobials such as chitosan, lactic acid, fermented pollen, grapefruit extract were applied with heat at $85^{\circ}C$ for 30 min, more than 1 log CFU/mL spores were additionally inactivated compared to only heat treatment without antimicrobials. Imposition of $60^{\circ}C$ to B. cereus spores with the higher concentration of 5.0%(v/v) lactic acid or 2.5%(w/v) thiamine dilaurylsulfate for the longer time incubation of 24 hr resulted in 3 log CFU/mL spore inactivation. This work showed that low concentrations of commercial antimicrobials by themselves did not inactivate B. cereus spores. However, when physical processes such as heat were combined together, antimicrobials showed a synergistic effect against B. cereus spores.