• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.685-691
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• 2005

In this study, high performance waste heat recovery heat exchanger was developed using the bayonet tube with spiral serrated fins. Especially, heat exchanger of the bayonet tube type was operated well because of double water passes mechanism and characteristics. A cooling water Passes down inner tubes to thimble-form tubes, then flows back up as it boils. The heat exchanger of bayonet tube type was composed of steel tube with 7channels$(I.D_1\;14mm.\;I.D_2\;31.6mm)$ and spiral serrated fins. The performance tests were conducted under the following conditions A cooling water flow rate was 273kg/h and engine l·pm was varied from 750rpm to 3500 rpm. From the experimental result. waste heat recovery was 9.21kW when engine rpm was 3500. and pressure drop was $15\~260mmHg/m^3$ The effectiveness of heat exchanger was about /$0.7\~0.9$. The performance of heat exchanger was evaluated by using the $\varepsilon-NTU$ method. In the study the NTU of the heat exchanger was $1.57\~2.33$.

• Journal of Environmental Health Sciences
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• v.40 no.1
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• pp.47-54
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• 2014

Objectives: The purpose of this study is to evaluate the characteristics of leachate discharged from livestock burial sites in Gangwondo resulting from foot-and-mouth disease by monitoring the water quality at the survey tube-wells installed near livestock burial sites in order to investigate the effect of the leachate on the quality of nearby underground water and suggest a water pollution level in accordance with water quality evaluation criteria. Methods: To minimize the secondary environmental pollution damage caused by leachate at burial sites of livestock killed by foot-and-mouth disease, this study analyzed the leachate directly discharged from burial sites and installed survey tube-wells within 300 meters of livestock burial sites and investigated water quality as a means to ascertain the environmental effect of the leachate from the burial sites. In accordance with environmental management guidelines on livestock burial sites, this research investigated the water quality in the survey tube-wells in fifty five burial sites in Gangwondo. The elements investigated were $NH_3$-N, $Cl^-$, $NO_3$-N, conductivity, and E. coli. Water quality was monitored from 2011 to 2013. Results: The water quality from the drain pipe at the location of leachate from livestock burial sites showed BOD 37,209 mg/L, COD 8,829 mg/L, $NH_3$-N 3,633 mg/L, and $Cl^-$ 580 mg/L. According to the monitoring results of water quality ($Cl^-$, $NH_3$-N, conductivity) at the survey tube-wells, there was suspicion that 13 out of 55 burial sites discharged leachate, five sites discharged highly concentrated leachate (13%): one in Gangneung, one in Wonju, and three in Cheorwon. Conclusion: It was judged that out of thirteen observation wells which showed a possibility of discharged leachate, three survey tube-wells have established the discharge effect of leachate at burial sites up to recently. Therefore, it is judged that it is necessary to continue monitoring them and devise additional measures.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.145-150
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• 2020

Water wall tube is one of the major factors consisting of a fluidized bed boiler and it plays very important role for the generation of electricity within the boiler. But these water wall tubes within the fluidized bed boiler are subject to the ware and corrosion caused by the high temperature gas and the flowing medium. If water leak is occurred, the secondary damage by the water leak will occur. As a result of that, the power generation efficiency decreases noticeably. Therefore, the maintenance of the water wall tube is very important. In this study, we designed a exciter sensor based on simulation and composed a remote field eddy current system for the defect evaluation of the outer water wall tube. Starting from the shape design of exciter, we conducted simulations for various design factors such as the water wall tube size, material, frequency, lift-off and so on. Based on the results, we designed the optimum exciter sensor for the water wall tube test within the fluidized bed boiler.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.550-560
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• 1996

Recently, fluidized bed heat exchangers with circulating liquid are widely used in a number of places-chemical, process, food concentration, waste water treatment facilities, etc. In a circulating heat exchanger, solid particles circulate with the liquid, thereby increase the heat transfer and reduce the fouling potential of the heat exchanger. In this study, glass beads were circulated through a vertical tube. The pressure loss and the heat transfer coefficient were measured. At low flow velocities, glass beads enhanced the heat transfer considerably. The enhancement increased as the volume fraction of the glass beads increased. The pressure loss showed a similar trend. From the observed particle behavior near tube wall, a possible explanation of the trend is provided.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.164-169
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• 2001

There is a chilled ceiling panel which carries out the air conditioning by radiation and convection between the room and cold ceiling panel surface. In order to verify heat transfer characteristics between them in cooling system with radiant chilled ceiling panel, analytical and experimental studies were performed for various design and operating parameters such as tube space and diameter, inlet water temperature, mass flow rate, cooling load, and so on. In this study, we found that the tube space and inlet water temperature were more important elements than the tube diameter and water flow rate for the performance of radiant chilled ceiling panel. The cooling capacity of the radiant chilled ceiling panel had the maximum value of $65W/m^{2}$ because the highest cooling capacity was limited by the condensation on the panel surface. The results of comparison between numerical analysis and experiment showed a resonable agreement qualitatively, especially for low cooling capacity.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1756-1766
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• 2003

Numerical modeling is carried out to investigate forced convective heat transfer to near-critical water in developing laminar flow through a circular tube. Due to large variations of thermo-physical properties such as density, specific heat, viscosity, and thermal conductivity near thermodynamic critical point, heat transfer characteristics show quite different behavior compared with pure forced convection. With flow acceleration along the tube unusual behavior of heat transfer coefficient and friction factor occurs when the fluid enthalpy passes through pseudocritical point of pressure in the tube. There is also a transition behavior from liquid-like phase to gas-like phase in the developing region. Numerical results with constant heat flux boundary conditions are obtained for reduced pressures from 1.09 to 1.99. Graphical results for velocity, temperature, and heat transfer coefficient with Stanton number are presented and analyzed.

• Tribology and Lubricants
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• v.14 no.4
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• pp.88-94
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• 1998

The fretting wear characteristics of Zircaloy-4 tube in light water were investigated experimentally. A fretting wear tester was designed to be suitable for this fretting test. This study was focused on the effects due to the combination of normal load, slip amplitude and number of cycles as the main factors of fretting. The results of this study showed that the wear volume increased abruptly at slip amplitude above 100 ${\mu}{\textrm}{m}$, which is defined as critical slip amplitude of Zircaloy-4 tube in light water, and that under 160 ${\mu}{\textrm}{m}$ the wear volume decreased as load increased at the same slip amplitude.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.55-63
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• 1998

The fretting wear characteristics of Zircaloy-4 tube in light water were investigated experimentally. A fretting wear tester was designed to be suitable for this fretting test. This study was focused on the effects due to the combination of normal load, slip amplitude and number of cycles as the main factors of fretting. The results of this study showed that the wear volume increased abruptly at slip amplitude above 100$\mu$m, which is defined as critical slip amplitude of Zircaloy-4 tube in light water, and that under 160$\mu$m the wear volume decreased as load increased at the same slip amplitude.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.04a
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• pp.121-131
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• 1996

Recently, circulating liquid fluidized bed heat exchangers are widely used in a number of places - chemical, process, food concentration, waste water treatment facilities, etc. In a circulating heat exchanger, solid particles circulate with the liquid, thereby increase the heat transfer and reduce the fouling potential of the heat exchanger. In this study, glass beads were circulated through a vertical tube. The pressure loss and the heat transfer coefficient were measured. At low flow velocities, glass beads enhanced the heat transfer considerably. The enhancement increased as the volume fraction of the glass beads increased. It also increased as the particle diameter increased. The pressure loss showed a similar trend. From the observed particle behavior near tube wall, a possible explanation of the trend is provided.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.454-461
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• 1997

Heat transfer and pressure drop for single phase flow of water in circular smooth and micro-fin tubes are measured. Copper tubes of 9.52 and 7mm outer diameter were used. The internal roughness in micro-fin tubes was formed by spiral grooves having $25^{\circ}$ helx angle, 0. 12mm fin height and 0.454mm pitch in 9.52mm tubes; $18^{\circ}$ helix angle, 0.15mm fin height and 0.322mm pitch in 7mm tubes. The measured friction factor and heat transfer coefficient are compared with relevant previous works, and the correlations for micro-fin tube are developed.