• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.2
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• pp.99-105
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• 2017

Many composite materials are used in the aerospace industry because of their excellent mechanical properties. However, the nature of aviation exposes these materials to high temperature and high moisture conditions depending on climate, location, and altitude. Therefore, the molecular arrangement chemical properties, and mechanical properties of composite materials can be changed under these conditions. As a result, surface disruptions and cracks can be created. Consequently, moisture-impregnating defects can be induced due to the crack and delamination of composite materials as they are repeatedly exposed to moisture absorption moisture release, fatigue environment, temperature changes, and fluid pressure changes. This study evaluates the possibility of detecting the moisture-impregnating defects of CFRP and GFRP honeycomb structure sandwich composite materials, which are the composite materials in the aircraft structure, by using an active infrared thermography technology among non-destructive testing methods. In all experiments, it was possible to distinguish the area and a number of CFRP composite materials more clearly than those of GFRP composite material. The highest detection rate was observed in the heating duration of 50 mHz and the low detection rate was at the heating duration of over 500 mHz. The reflection method showed a higher detection rate than the transmission method.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.94-98
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• 2009

The bubble point pressures of dimethyl carbonate and carbon dioxide mixtures were measured by using a high-pressure experimental apparatus equipped with a variable-volume view cell, at various $CO_2$ compositions in the range of temperatures above the critical temperature of $CO_2$ and below the critical temperature of dimethyl carbonate. The experimental bubble point pressure data were correlated with the Peng-Robinson equation of state (PR-EOS) to estimate the corresponding dew point compositions at equilibrium with the bubble point compositions. The experimentally measured bubble point pressures gave good agreement with those calculated by the PR-EOS. The variable-volume view cell equipment was verified to be an easy and quick way to measure the bubble point pressures of high-pressure compressible fluid mixtures.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.159-159
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• 2011

Among the semiconductor ternary compounds in the I-III-$VI_2$ series, $CulnS_2$ ($CulnSe_2$) are one of the promising materials for photovoltaic applications because of the suitability of their electrical and optical properties. The $CuInS_2$ thin film is one of I-III-$VI_2$ type semiconductors, which crystallizes in the chalcopyrite structure. Its direct band gap of 1.5 eV, high absorption coefficient and environmental viewpoint that $CuInS_2$ does not contain any toxic constituents make it suitable for terrestrial photovoltaic applications. A variety of techniques have been applied to deposit $CuInS_2$ thin films, such as single/double source evaporation, coevaporation, rf sputtering, chemical vapor deposition and chemical spray pyrolysis. This is the first report that $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) technique which is a novel and attractive method because thin films with high deposition rate can be grown at very low cost. In this study, $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) method which employs a nozzle expansion. The mixed fluid is expanded through the nozzle into the chamber evacuated in a lower pressure to deposit $CuInS_2$ films on Mo coated glass substrate. In this AJD system, the characteristics of $CuInS_2$ films are dependent on various deposition parameters, such as compositional ratio of precursor solution, flow rate of carrier gas, stagnation pressure, substrate temperature, nozzle shape, nozzle size and chamber pressure, etc. In this report, $CuInS_2$ thin films are deposited using the deposition parameters such as the compositional ratio of the precursor solution and the substrate temperature. The deposited $CuInS_2$ thin films will be analyzed in terms of deposition rate, crystal structure, and optical properties.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.19-27
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• 2007

The previous study was conducted to develop an air source multi heat pump system that could be operated with the solar collector and air source heat exchangers as heat source of the system. There is a winter-sowing problems in air source multi heat pump system when the outdoor temperature goes down under freezing point. The winter-sowing problem was solved by adapting R-22 refrigerant as working fluid in the previous study. However, when the system operated at high temperature, another problems are come out such as overheating of the solar collector outlet which lead to the superheat of the compressor inlet of the heat pump system. The condition could deteriorates a compressor in some case. In this study, we installed the anti-superheating devices on the previously developed system. As results of system performance test, COP of the system with anti-superheating technique is 2.4. It is a little improved COP compare to previous study's 2.23. In the results of multi heat source heating system, during operating solar collector, COP is relatively high between $200\;W/m^2$ and $400\;W/m^2$ solar intensity. It is recommended to extend the study on performance optimization with balancing the solar collect and capacity of compressor at higher solar irradiation conditions.

• Journal of Veterinary Clinics
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• v.26 no.3
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• pp.306-310
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• 2009

Mass mortality was occurred in adult koi carp(Cyprinus carpio) at a private pond near Samchunpo city in the early November, 2007. Its water temperature was $11^{\circ}C$ and turbidity was very high. The fishes diseased were shown widely distributed hemorrhages, deep ulcerations on the whole body surface and severe erosions in the all fins. In necropsy, excess ascitic fluid was observed and spleen and kidney affected were enlarged. In microscopic observation, it was examined widely distributed severe dermal ulceration, multifocal gill lamella hyperplasia, severe fibrinous pericarditis, multifocal nephritis and hepatitis. The bacteria suspected were isolated using tryptone soya agar and identified as motile Aeromonas hydrophila as results of biochemical tests using API 20E and 20NE. According to previous reports, A. hydrophila infection were mainly occurred in fingerling at high temperature. However, this case exhibited that A. hydrophila infection can develop on adult koi carp even in the winter season.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.377-383
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• 2005

Because explosive fluid is used at high temperature or under high pressure in petrochemistry and refined oil equipment, the interest about safety of equipments is intensive. Specially, the safety of high pressure reactor vessel is required among them. The material selected in this study is 2.25Cr-1Mo steel that is widely used for high pressure reactor vessel material of petrochemical plant. Eight kinds of artificially aged specimens were prepared by differing from aging periods under three different temperatures. The material was iso-thermally heat treated at higher temperatures than $391^{\circ}C$ that is the operating temperature of high pressure reactor vessel. Vickers hardness properties and electrical resistivity properties about artificially aged material as well as un-aged material were measured, and master curves were made out from the correlation with larson-Miller parameter. And electrical resistivity properties as well as Victors hardness properties measured at high pressure reactor vessel of the field were compared with master curves made out in a laboratory. Degradation evaluation possibility in the field of high pressure reactor vessel by using electrical resistivity method was examined. Electrical resistivity property measured in the field is similar with that of artificially aged material in similar aging level.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1154-1161
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• 2006

Air drying equipment was built as a device for reduction of dewatered cake from wastewater and waterworks sludge and to reproduce it by reusable matter. Dewatered cake was supplied into the air drying equipment which operated by air velocity of 80 m/sec, air rate 30 $m^3/min$ and air temperature of $40^{\circ}C$, and dried to produce the dried powder. The air drying equipment was composed of the air ejector which made high-speed fluid field, and cyclone which made circling fluid field. Dewatered cake was crushed at the high-speed zone as first step, and formed into dried powder of sphere shape by the collision between particles at the circling fluid zone.. Wastewater sludge with water content of 82.5 wt% was supplied 1.0 kg/min into air drying equipment and produced the dried powder which had the water content of 62.3 wt% and mass median diameter of 2.4 mm after process. At that time, it was analyzed that water removal rate was 0.1 $H_2O{\Delta}kg/min{\cdot}DS$ kg and air consumption was 170 $m^3/DS$ kg. Under same experimental conditions, when waterworks sludge was dried, water content of dried powder decrease to 47.5 wt% and mass median diameter decrease 2.1 mm and water removal rate increase 0.13 $H_2O{\Delta}kg/min{\cdot}DS$ kg. Air consumption increase 180 $m^3/DS$ kg with comparison to the results of wastewater sludge. Therefore, this technology was evaluated that drying the dewatered cake of waterworks sludge was more efficient than wastewater sludge, and also economical sludge handling technology due to drying the cake by only air.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.821-830
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction steam line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical results using the FLUENT code and the down scale experimental data on effect of geometry of the impingement baffle plate on the shell wall thinning. Additionally, a new type impingement baffle plate was installed above the impingement baffle plate in the feedwater heater and then the numerical and experimental study were performed in the same progress.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.61-71
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• 2017

The tracer gas method has an advantage that can estimate total and local ventilation rate by tracing air flow. However, the field measurement using tracer gas has disadvantages such as danger, inefficiency, and high cost. Therefore, the aim of this study was to evaluate ventilation rate in pig house by using the thermal distribution data rather than tracer gas. Especially, LMA (Local Mean Age), which is an index based on the age of air theory, was used to evaluate the ventilation rate in pig house. Firstly, the field experiment was conducted to measure micro-climate inside pig house, such as the air temperature, $CO_2$ concentration and wind velocity. And then, LMA was calculated based on the decay of $CO_2$ concentration and air temperature, respectively. This study compared between LMA determined by $CO_2$ concentration and air temperature; the average error and root mean square error were 3.76 s and 5.34 s. From these results, it was determined that thermal distribution data could be used for estimation of LMA. Finally, CFD (Computational fluid dynamic) model was validated using LMA and wind velocity. The mesh size was designed to be 0.1 m based on the grid independence test, and the Standard $k-{\omega}$ model was eventually chosen as the proper turbulence model. The developed CFD model was highly appropriate for evaluating the ventilation rate in pig house.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.647-655
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• 2021

The IMO (International Maritime Organization) is discussing the improvement of energy ef iciency of ships in order to reduce greenhouse gas emissions from ships. Currently, by applying an ORC power generation system using waste heat generated from ships, high energy conversion efficiency can be expected from ships. This technology uses an organic medium based on Freon or hydrocarbons as the working fluid, which evaporates at a lower temperature range than water. Through this, it is possible to generate steam (gas) and generate power at a low and low temperature relatively. In this study, the analysis of heat flow between the refrigerant and waste heat in the ORC power generation system, which is an organic Rankine cycle, is analyzed using 3D simulation techniques to determine the temperature change, velocity change, pressure change, and mass change of the fluid flowing of the WHRU (Waste Heat Recovery Unit) inside and the outside the structure. The purpose of this study is to analyze how the mass change affects the structure, and this study analyzed the heat transfer of the heat exchanger from the refrigerant and the exhaust gas of the ship's main engine in the ORC power generation system using this technique.