• Journal of Power System Engineering
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• v.18 no.2
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• pp.37-42
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• 2014

The purpose of this paper is to investigate polarization characteristics of heat-treated Ni-based self-flux alloy coating in alkaline solution. Ni-based self-flux alloy powder was sprayed to a steel substrate using flame spray process, and heat treatments were performed in a vacuum furnace at $800^{\circ}C$, $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. After heat treatments, corrosion tests were carried out using potentiostat/galvanostat at solution with pH 8 and pH 13. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be analyzed from polarization curve. Anticorrosive effect of heat-treated coating at solution with pH 8 was relatively greater than at solution with pH 13. Heat-treated coating at $1100^{\circ}C$ showed the greatest anti-corrosion characteristics in alkaline solution.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.294-301
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• 2014

This study focuses on analysis and comparison of entropy generation in various cross-sectional ducts along with fully developed laminar flow and constant uniform wall heat flux. The obtained results were compared in ducts with circular, semicircular, and rectangular with semicircular ends, equilateral triangular, and square and symmetrical hexagonal cross-sectional areas. These results were separately studied for aspect ratio of different rectangular shapes. Characteristics of fluid were considered at average temperature between outlet and inlet ducts. Results showed that factors such as Reynolds number, cross section, hydraulic diameter, heat flux and aspect ratio were effective on entropy generation, and these effects are more evident than heat flux and occur more in high heat fluxes. Considering the performed comparisons, it seems that semicircular and circular cross section generates less entropy than other cross sections.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.111-115
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• 2006

To clarify the hydraulic and thermal characteristics of ice slurry which made from 6.5% ethylene glycol-water solution flow in the double tube and plate type heat exchanger, experimental studies were performed. The mass flux and Ice fraction of ice slurry were varied from 800 to $3,500 kg/m^2s$(or 7 to 17 kg/min) and from 0 to 25%, respectively. During the experiment, it was found that the measured pressure drop and heat transfer rate increase with the mass flux and ice fraction; however the effect of ice fraction appears not to be significant at high mass flux region. At the region of low mass flux, a sharp increase in the pressure drop and heat transfer rate were observed depends on mass flux.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.74-79
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• 2011

Concentration characteristics of the KIER solar furnace are analyzed with a heat flux measurement technique. Total heat capacity of 40kW was confirmed within 1.04% average error, and the normalized maximum heat flux of 3,452 $kW/m^2$ was proved. Non-Gaussian flux distribution in the vertical direction implies that reflectors should not be random rather inclined downwards. Moreover, we characterized flux distribution variations with furnace blind opening ratio, distance from the focal plane, and misalignment of the measurement system. Based on the results, the heat flux distribution can be simply estimated once reflectivity and direct normal insolation values are known. This study will be helpful to the design and the performance evaluation of receivers or chemical reactors.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.5
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• pp.75-82
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• 2010

To study the combustion characteristics of forest fuel by fire intensity, the experiment of combustion characteristics on Pinus Densiflora living leaves, which is the weakest species to the forest fire, was delivered, using variables of heat flux(25 kW/$m^2$, 50 kW/$m^2$, 75 kW/$m^2$). With the equipment of Cone calorimeter, the characteristics of ignition, heat, smoke release, CO and $CO_2$ release, and mass loss were analyzed. Pinus Densiflora living leaves containing moisture of 60.66% were not ignited at the heat flux of variables 25 kW/$m^2$, 50 kW/$m^2$, 75 kW/$m^2$. In proportion to the heat flux value, heat release amount and heat release rate reached maximum value rapidly: higher variables came to the maximum by the half rapidity and the maximum value were twice higher than the former lower variables respectively. As for the smoke release, the less heat flux the variable had, the more smoke release it had, due to incomplete combustion. The release amount of CO and $CO_2$ had more maximum value as the heat flux increased and more radiant heat meaned more carbon oxide. When the forest fire breaks out, therefore, a great amount of CO and $CO_2$ will be released by Pinus Densiflora.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1528-1535
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• 2009

Characteristics of R-22 and R-134a two-phase vaporization in horizontal small tubes were investigated experimentally. In order to obtain the local heat transfer coefficients, the test was ran under heat flux range of 10 to $40\;kW/m^2$, mass flux range of 200 to $600\;kg/m^2s$, saturation temperature range of 5 to $10^{\circ}C$, and quality up to 1.0. The test section, which was made of stainless steel tube and heated uniformly by applying an electric current to the tube directly, have inner tube diameters of 0.5, 1.5 and 3.0 mm, and lengths of 0.33 and 2.0 m. The effects on heat transfer coefficient of mass flux, heat flux and inner tube diameter were presented. The experimental heat transfer coefficients were compared with the predictions using existing heat transfer coefficient correlations. A new boiling heat transfer coefficient correlation based on the superposition model, with considering the laminar flow, was developed.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.262-268
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• 2008

The present paper dealt with flow heat transfer characteristics of R-410A vaporization in horizontal smooth microchannel. The test sections were made of stainless steel tube with inner diameters of 300 mm and length of 300 mm. The refrigerant was supplied with mass flux range of 260-600 kg/$m^2s$ and applied under operating heat flux range of 5-20 kW/$m^2$ using a direct electric current heating method. The in let saturation temperature was set at $10^{\circ}C$ and vapor quality up to 1.0. The influences of mass flux, heat flux and inner tube diameter on local heat transfer coefficients were presented. Comparison with existing heat transfer coefficient correlations was performed. An improved heat transfer coefficient correlation for refrigerant vaporization in microchannel based on superposition model was developed with a mean deviation of 14.01%.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.25-32
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• 2000

In this paper, experiments investigating the high-temperature region heat transfer coefficients for the spray cooling of hot flat plates were performed by down spray water using flat spray nozzles. The heat transfer surface is made of copper and is 100mm in length and 40mm in width and 15mm in thickness. The experimental condition of spray are as follows: temperatures of the water droplets are T=20~$80^{\circ}C$ and droplets volume fluxes are D=0.001565~0.010438$m^3/m^2s$. Next, correlating equations for the heat transfer characteristics of spray cooling in the high temperature region are developed from the effects of droplets volume flux and the surface temperature of heat transfer plate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.8
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• pp.748-755
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• 2004

Flow boiling heat transfer in small-diameter round tubes has been experimentally studied. The experimental apparatus consisted mainly of refrigerant pump, condenser, receiver, test section of a 1.67 mm inner-diameter round tube and pre-heater for control of refrigerant quality at the inlet of test section. To investigate the effect of bubble nucleation site characteristics of different tube materials, three different tubes of copper, aluminum and brass were used. The ranges of the major experimental parameters were 5∼30 ㎾/$m^2$ of the wall heat flux, 0.0∼0.9 of the inlet vapor quality and the refrigerant mass flux was fixed at 600 kg/$m^2$s. The experimental results showed that the flow boiling heat transfer coefficients in small tubes were affected only by heat flux, but independent of mass flux and vapor quality. The effect of tube material on flow boiling heat transfer was observed small.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.440-442
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• 2005