• Journal of Power System Engineering
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• v.4 no.1
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• pp.13-19
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• 2000

This study was conducted for the heat transfer reduction due to the clinker formed in the furnace of the thermal power plant. The thermal properties of clinker such as thermal conductivity, specific heat, density and void fraction were measured. The thermal conductivities of the clinker were ranged $0.32-0.54W/m{\cdot}K$ and the average specific heat and the void fraction were $930J/kg{\cdot}K$ and 0.36 respectively. The thermal resistance of clinker was the greatest among the thermal resistances. It was found that the clinker reduces more than 90% of the heat transfer if the clinker is thicker than 10 cm.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.3
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• pp.201-207
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• 2004

Redox characteristics of metal oxide for hydrogen production by thermochemical water-splitting were investigated. $CuFe_2O_4$ as a redox pair that had a different molar ratio of Cu and Fe were prepared by co-precipitation method. Hydrogen production consisted of water-splitting step and thermal reduction step was performed below 1200K. Redox characteristics of Cu-ferrites were studied using the thermal gravimetric analysis technique. Also, structure change of Cu-ferrite during thermal reduction was investigated using the high temperature controlled XRD. In results, oxygen release of Cu-ferrite during the thermal reduction was initiated at oxygen site combined with Cu. Consequently, oxygen release amount of Cu-ferrite was increased with increase of Cu molar ratio of Cu-ferrite. It was found that thermal reduction of Cu-ferrite was begun at $875^\circ{C}$. It was confirmed that structure of Cu-ferrite was changed to metal and cation excess metal oxide during the thermal reduction step.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.103-109
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• 2010

Anaerobic digestion has been widely used for the treatment of sludge, which is generated from the municipal and industrial wastewater treatment, for its volume reduction and methane production. Many researches on sludge pre-treatment have been carried out in order to enhance the performance of anaerobic digestion by increasing the hydrolysis of sludge which is the rate limiting step of anaerobic digestion. In this study, the effect of pre-treatment on sludge hydrolysis(solubilization), methane production and sludge reduction by anaerobic digestion after thermal, ultrasonic, and thermal-alkali sludge treatment were compared. Thermal-alkali treatment showed 67 and 70% solubilization with municipal and industrial wastewater sludge, respectively, while ultrasonic treatment and thermal treatment gave similar solubilization efficiency of 40% or more. Methane content of the anaerobic digestion gas reached 45~70% and pretreated sludge gave higher methane content than the control sludge. Methane production of thermal, ultrasonic, and thermal-alkali pre-treatment gave 2.6, 2.7, 3.5 times of municipal control sludge and 3.5, 4.1, 4.2 times of industrial control sludge, respectively. Sludge reduction of pre-treated sludge after anaerobic digestion gave 5~19% point higher than that of control sludge, and thermal-alkali treatment showed higher reduction efficiency than thermal and ultrasonic treatment. The results proved that pre-treatment contributed significantly not only for the methane production but also for the cost reduction of sludge treatment and disposal, and thermal-alkali treatment gave the best performance for the sludge treatment.

• Journal of the Korean Society of Combustion
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• v.4 no.2
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• pp.97-108
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• 1999

This numerical study was to investigate the effect of $CO_2$ addition on the structures and NOx formation characteristics in $CH_4$ counterflow diffusion flame. The importance of radiation effect was identified and $CO_2$ addition effect was investigated in terms of thermal and chemical reaction effect. Also the causes of NOx reduction were clarified by separation method of each formation mechanisms. The results were as follows : The radiation effect was intensified by $CO_2$ addition. Thermal effect mainly contributed to the changes in flame structure and the amount of NO formation but the chemical reaction effect also cannot be neglected. The reduction of thermal NO was dominant with respect to reduction rate, but that of prompt NO was dominant with respect to total amount.

• Transactions on Electrical and Electronic Materials
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• v.16 no.5
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• pp.274-279
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• 2015

Reduced graphite oxides (rGOs) were prepared by the common graphite oxidation method and the subsequent reductions. The reduction of graphite oxides (GOs) was conducted chemically and/or thermally. To further reduce the as-prepared rGOs, GOs were treated with chemical/thermal reductions or thermal/chemical reductions, in which the reduction sequence was also considered. The structural changes of as-prepared rGOs, depending on reduction methods, were investigated by X-ray diffraction analyses, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. In addition, we discuss the structural change of the rGOs and their closely related physical and electrical properties, such as thermogravimetry, nitrogen adsorption isotherm, and sheet resistance.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.679-686
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• 1999

This study is to investigate the effect of a substantial drag reduction caused by the polymer(A611P) when the working fluids flow to the vertical direction in the vertical cylindrical equipment of closed flow system. The drag reduction is associated with the mechanical degrada-tion thermal degradation and heat transfer. By ignore the heat fluxs within the closed system the pressure drop due to the polymer concentration the flow velocity and flow time have been mea-sured. By taking into account the mechanical and thermal degradation in the closed system an experiment has been focused on the determination of the condition which could improve the pump capacity in the heat union electric power plant. Under the condition of non-boiling it has been found out that the change of heat flux has little influence on the drag reduction.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.1
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• pp.32-38
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• 2004

Thermal behaviors of $(Cu_{0.5}Mn_{0.5})Fe_2O_4$, prepared by a solid method, were investigated for $H_2$ production by a thermochemical cycle. The thermal reduction of $(Cu_{0.5}Mn_{0.5})Fe_2O_4$ started from $300^\circ{C}$ and the weight loss was 1.3 wt% up to 1200. XRD shows the prepared ferrite has the spinel structure with a lattice constant of $8.414{\AA}$ and changed to the oxygen deficient structure by thermal reduction. Oxygen and hydrogen can be separately produced by the cycles of thermal reduction and water oxidation of the oxygen deficient ferrite.

• Journal of Biosystems Engineering
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• v.15 no.2
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• pp.123-133
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• 1990

Thermal performance of a solar heating plastic greenhouse designed for a hydroponic system was studied. The system was constructed with the air-water heat exchanger and thermal storage tank that were combined with hydroponic water beds. Experiments were carried out to investigate the daily average heat stored and released in thermal storage tank, average solar energy collection efficiency, average coefficient of performance, average oil reduction factor of thermal storage system, and the heat transfer coefficient during the nighttime in plastic greenhouse. The results obtained in the present study are summarized as follows. 1. Daily average heat stored in thermal storage tank and released from the thermal storage tank was 1,259 and $797KJ/m^2$ day, respectively. 2. The average solar energy collection efficiency of thermal storage tank was 0.125 during the experiment period. And the average coefficient of performance of thermal storage system in plastic greenhouse was 3.6. 3. The average oil reduction factor of thermal storage system and the heat transfer coefficient during the nighttime in plastic greenhouse were found to be 0.52 and $4.3W/m^2\;hr\;^{\circ}C$, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.1
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• pp.15-21
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• 2015

The purpose of this paper is to analyze thermal characteristics of the heat sinks to maximize the thermal diffusivity for LED floodlight. The 2 kind of samples were prepared by vapor chamber manufacturing technology using the heat pipe principle. It was analyzed the maximum temperature reduction effect and the thermal diffusion from the heat source depending on the types of chambers with 3 kind of working fluids. As a result, it was confirmed that thermal conductivity 23% increased, GVC-R type than IVC-R type.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.24-31
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• 2002

An experimental study was conducted to investigate the effects of EGR (Exhaust Gas Recirculation) variables on performance and emission characteristics in a 2-liter 4-cylinder spark-ignition LPG fuelled engine. The effects of EGR on the reduction of thermal loading at exhaust manifold were also investigated because the reduced gas temperature is desirable for the reliability of an engine in light of both thermal efficiency and material issue of exhaust manifold. The steady-state tests show that the brake thermal efficiency increased and the brake specific fuel consumption decreased with the increase of EGR rate in hot EGR and with the decrease of EGR temperature in case of cooled EGR, while the stable combustion was maintained. The increase of EGR rate or the decrease of EGR temperature results in the reduction of NOx emission even in the increase of HC emission. Furthermore, decreasing EGR temperature by $180^{\circ}C$ enabled the reduction of exhaust gas temperature by $15^{\circ}C$ in cooled EGR test at 1600rpm/370kPa BMEP operation, and consequently the reduction of thermal load at exhaust. The optimization strategy of EGR application is to be discussed by the investigation on the effect of geometrical characteristics of EGR-supplying pipe line.