• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.27-35
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• 2017

The amount and quality of waste heat from a resource recovery facility were measured. The temperature of exhaust gas was $176.6^{\circ}C$ and the amount of that was 13.8 kg/s. This research designed a waste heat recovery system whose working fluid is R-245fa. It simulated three study cases as follows. In simulation of a basic ORC system, the turbine power output and thermal efficiency were respectively 96.56 kW, 14.3%. In simulation of a superheater connection, 0.09% of efficiency could be improved due to the increase of enthalpy by overheating of working fluid, but the obtained output was decreased with 16.58kW because of the decrease of working fluid mass. In simulation of a process heater connection, efficiency was increased up to 38.51%.

• Economic and Environmental Geology
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• v.45 no.1
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• pp.59-68
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• 2012

With the decline in discoveries of new oil fields and increasing demand from developing countries it is believed that enhanced oil recovery (EOR) technologies will play a key role to meet the energy demand in years to come. Based on the recently-published data, this paper discusses current status of global EOR market and technical development trends. The EOR market includes oil produced through various EOR recovery methods, such as thermal recovery, gas injection, chemical injection. Also, EOR methods are addressed screening criteria by reservoir and fluid characteristics including lithology, depth, thickness, and oil properties such as composition and gravity. Finally, the examples of field applied by various EOR methods are discussed with respect to reservoir characteristics and performance.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.4
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• pp.454-459
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• 2011

In this study, the recovery rate of Tedlar bag (T) sampler was investigated in comparison to polyester aluminum bag (P) sampler. To derive the comparative data sets for the relative performance between different samplers, a series of calibration experiments were performed by using 1 ppb standard of four offensive reduced sulfur compounds (RSC) odorants ($H_2S$, $CH_3SH$, DMS, and DMDS) along with $SO_2$ and $CS_2$. All the analysis was made by gas chromatography/pulsed flame photometric detector (GC/PFPD) combined with air server/thermal desorber (AS/TD). The measurement data were obtained by loading gaseous standards (1 ppb) at 3 injection volumes (250, 500 and 1,000 mL) at three intervals (0, 24 and 72 hrs). The recovery rates (RR) of P sampler were computed against the slope values of T sampler. According to our analysis, P sampler exhibits slightly enhanced loss relative to T, especially with light RSCs ($H_2S$ and $CH_3SH$). At day 0, RR for the two were 88 and 85%, respectively. Such reduction proceeded rather rapidly in the case of $H_2S$ through time. However, P sampler was more stable to store $SO_2$ unlike others. Despite slightly reduced recovery, P sampler appears as a good replacement of T sampler.

• Journal of Energy Engineering
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• v.17 no.3
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• pp.161-166
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• 2008

The purpose of this study is to apprehend the behavior of exhaust gas flow from gas turbine during part load operation in Heat Recovery Steam Generator. As a first step of this work, internal flow characteristics according to HRSG types were examined by CFD analysis. Next step, tube temperature according to gas turbine 53% and 100% load conditions were calculated by results of CFD and those were compared with temperature data gathered from real plant. Finally, thermal performance due to part load operation was calculated to estimate the influence of heat transfer in superheater. In addition, new type of device is suggested to eliminate the uneven temperature distribution of tubes during part load operation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1412-1419
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• 2003

Heat regenerator occupied by regenerative materials improves thermal efficiency of combustion system through the recovery of sensible heat of exhaust gases. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of regenerator with spherical particles, was numerically analyzed to evaluate the heat transfer and pressure losses and to derive the design parameter for heat regenerator. It is confirmed that the computational results, such as air preheat temperature, exhausted gases outlet temperature, and pressure losses, agreed well with the experimental data. The thermal flow in heat regenerator varies with porosity, configuration of regenerator and diameter of regenerative particle. As the gas velocity increases with decreasing the cross-sectional area of the regenerator, the heat transfer between gas and particle enhances and pressure losses decrease. As particle diameter decreases, the air is preheated higher and the exhaust gases are cooled lower with the increase of pressure losses. Assuming a given exhaust gases temperature at the regenerator outlet, the regenerator need to be linearly lengthened with inlet Reynolds number of exhaust gases, which is defined as a regenerator design parameter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.4
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• pp.208-215
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• 2013

An experimental study of an ORC (Organic Rankine Cycle) system has been performed for small-scale applications in the range of a few kW for low-grade-recovery heat sources. The ORC system was equipped with a scroll expander. Experimental tests were carried out using this system, and showed good performance and reliability for the small-scale system. The effects of various operating conditions were selected as the main parameters for the performance of ORC system, such as the expander speeds and mass flow rates of R-134a for expander inlet temperatures ranging from $100^{\circ}C$ to $190^{\circ}C$, as well as the thermal power, thermal efficiency, expansion efficiency, and volumetric efficiency.

• Journal of Hydrogen and New Energy
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• v.21 no.6
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• pp.570-579
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• 2010

Since the temperature of waste heat source is relatively low, it is difficult to maintain high level of efficiency in power generation when the waste heat recovery is employed in the system. In an effort to improve the thermal efficiency and power output, use of ammonia-water mixture as a working fluid in the power cycle becomes a viable option. In this work, the performance of ammonia-water mixture based Rankine cycle is thoroughly investigated in order to maximize the power generation from the low temperature waste heat. In analyzing the power cycle, several key system parameters such as mass fraction of ammonia in the mixture and turbine inlet pressure are studied to examine their effects on the system performance. The results of the cycle analysis find a substantial increase both in power output and thermal efficiency if the fraction of ammonia increases in the working fluid.

• Fashion & Textile Research Journal
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• v.11 no.6
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• pp.947-952
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• 2009

The purpose of this study is to analyze skin wettedness($w$) used as the rate index of thermal comfort, and to evaluate the wear comfort of outdoorwear. Skin wettedness is widely used to express the degree of thermal comfort. If skin wettedness exceeds a certain threshold, the body feels damp and discomfort. An experiment which consisted of rest(30 min), exercise(30 min) and recovery(20 min) periods was administered in a climate chamber with 10 healthy male participants. Two kinds of outdoorwears made of 100% cotton fabrics (Control) and specially engineered fabrics having feature of quick sweat absorbency and high speed drying fabric (Functional) were evaluated in the experiment. The condition of climate chamber was controlled according to the thermal insulation of 4 kinds of experimental ensembles(E1~E4). Total sweat loss, sweat loss absorbed into clothing and skin temperature were measured. Skin wettedness was calculated from the ratio of evaporative rate to the maximal evaporative capacity. Skin wettedness of 'Functional' was lower than 'Control' in the 3 kinds of ensembles(E1, E2, E4) because the materials of 'Functional' were composed of quick sweat absorbency and high speed drying fabrics, water vapour permeability and waterproof fabrics.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.407-412
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• 2015

A preconcentration procedure for determination of palladium by laser thermal lens spectrometry (TLS) is proposed. It is based on cloud point extraction of palladium(II) ions as 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminoaniline (3,5-diCl-PADMA) complexes using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The effects of various experimental conditions such as pH, concentration of ligand and surfactant, equilibration temperature and time on cloud point extraction were studied. Under the optimized conditions, the calibration graph was linear in the range of 0.15~6 ng mL⁻¹, and the detection limit was 0.04 ng mL⁻¹ with an enrichment factor of 22. The sensitivity was enhanced by 846 times when compared with the conventional spectrophotometric method. The recovery of palladium was in the range of 96.6%~104.0%. The proposed method was applied to the determination of palladium in water samples.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.6
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• pp.697-705
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• 2014

A single chip Programmable AC to DC Power Converter, consisting of wide band gap SiC MOSFET and SiC diodes, has been proposed which converts high frequency ac voltage to a conditioned dc output voltage at user defined given power level. The converter has high conversion efficiency because of negligible reverse recovery current in SiC diode and SiC MOSFET. High frequency operation reduces the need of bigger size inductor. Lead inductors are enough to maintain current continuity. A complete electrical analysis, die area estimation and thermal analysis of the converter has been presented. It has been found that settling time and peak overshoot voltage across the device has reduced significantly when SiC devices are used with respect to Si devices. Reduction in peak overshoot also increases the converter efficiency. The total package substrate dimension of the converter circuit is only $5mm{\times}5mm$. Thermal analysis performed in the paper shows that these devices would be very useful for use as miniaturized power converters for load currents of up to 5-7 amp, keeping the package thermal conductivity limitation in mind. The converter is ideal for voltage requirements for sub-5 V level power supplies for high temperatures and space electronics systems.