• Corrosion Science and Technology
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• v.23 no.3
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• pp.246-254
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• 2024

Recently, coal-fired power plants are experiencing many problems that they have never experienced before due to an increase in flexible operation. In particular, a two-phase flow accelerated corrosion on water wall tubes in a boiler has not been detected overseas or domestically. There is no response plan to deal with such corrosion problem either. However, oxide film damage and tube material corrosion due to a two-phase flow accelerated corrosion are being discovered on water wall boiler tubes of domestic coal-fired power plants recently. If this situation is severe, it can cause enormous damage such as tube rupture. Therefore, in this paper, in order to prepare a response plan for a two-phase flow accelerated corrosion on water wall tubes in the future, differences between a two-phase flow accelerated corrosion and a single-phase flow accelerated corrosion were investigated and an example of discovery of a two-phase flow accelerated corrosion on water wall tubes was presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1127-1133
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• 2012

A finned-tube-type evaporator module has been proposed for a 2 t/h-class water-tube-type industrial boiler with multiple burners. The geometry of the fins was changed at each module to equalize the evaporation. The modules were designed by considering the energy balance at each row rather than by following a conventional bulk design procedure. The designed module was built into a 2 t/h-class water-tube-type boiler, and its performance was tested. A numerical simulation was also conducted to evaluate the two- or three-dimensional effects of factors such as the inlet conditions. The numerical simulation also included the conjugate heat transfer problem to predict the fin tip temperature. The heat transfer coefficient with fins is lower than that obtained from the empirical correlation of a bare tube. The fin tip temperature from CFD is higher than that from the analytical solution.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1692-1697
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• 2004

The once-through heat recovery steam generator is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of boiler is structurally simpler than drum type boiler. In drum type boiler, each tube play a well-defined role: water preheating, vaporization, superheating. Empirical equations are available to predict the average heat transfer coefficient for each regime. For once-through heat recovery steam generator, this is no more the case and mathematical models have to be adapted to account for the disappearance of drum type economizer, boiler, superheater. General equations have to be used for each tube of boiler, and actual heat transfer condition in each tube has to be identified.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.67-72
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• 2011

HRSG (Heat Recovery Steam Generator) is a boiler to recover heat from the exhaust gas of an engine and to generate steam for more power generation or process. For the HRSG, water-tube type boiler is commonly adopted to accommodate the working pressure or capacity requirement of the system. The water-tube type boiler has a steam drum to separate steam from the water-steam mixture supplied from the evaporator tube (riser). The drum should be sized properly to separate the steam by the gravity and auxiliary internals, such as a demister, which are installed to filter the steam. To size the steam drum and to estimate the filter efficiency of drum internals, the velocity distribution inside the drum needs to be identified. In the present study, a series of CFD has been conducted to find the velocity distributions inside steam drums for conventional HRSGs and water-tube type industrial boilers. The velocity distributions obtained from the simulation have been normalized and a correlation to predict them has been found. The correlation is applied to the steam drum design by determining a proper position of a demister to show proper separation performance.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1025-1030
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• 2008

We develop heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a heat recovery steam generator (HRSG). This heat recovery system has 4 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 10 bar and tested steam pressure is 4 bar. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). The test results of 100% boiler load show that heat transfer rate of 1st module is 49.7 Mcal/h which is 34% of total heat transfer rate and that of 2nd module is 82.6 Mcal/h which is 57% of total heat transfer rate. The reason of higher the heat transfer rate of 2nd module than that of 1st module is that the 2nd heat exchanger module has finned tubes instead of bare tube. The boiler load 50% results show that only 2 heat exchanger modules are needed to extract the heat from the flue gas to water. From this result, it is very important of optimum design of the first finned tube among all water tubes.

• Journal of the Korean Society of Industry Convergence
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• v.1 no.2
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• pp.13-19
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• 1998

A computer simulation program for the design of furnace witjin pakaged water-tube boilres is developed and the developed computer program is successfully applied to design the furnace for packaged water-tube boiler. The model by experiment and the model by Hottel are used to predict the exit gas temperature of furnace. The result by two models is discussed and is shown that in the case of constant cross section in furnace, the result is same but in changing the configuration of cross section, the difference by two models is not small.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.699-705
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• 1985

Heat transfer characteristics in terms of the tube wall-temperature and the enthalpy have been investigated utilizing ribbed (rifled) tubes in order to enhance heat transfer performance. Considerations were given for the cases of smooth tubes in order to compare with the case of ribbed tubes. The tilt angle of the experimental tubes are from 0.deg. to 90.deg. , in order to simulate the boiler water tubes having 15.deg.-90.deg. inclined angle in boiler nose and studded tubes (burner zones), Natural convection and forced convection (Re=1810) conditions were considered in the experiments. The experimental results for the effect for the tube inclination through a natural convection and forced convection are presented and it is shown that ribbed tubes permit an appreciable increase in heat transfer coefficients and consequently it means substantial reductions in boiler water wall tubes and heat exchanger surface areas.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.49-55
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• 2014

In this study, boiler tube thickness measurement and numerical analysis were conducted for standard 500MW coal-fired power plant in order to research the mechanism of tangential-fired boiler corrosion empirically. The most dominant corrosion mechanism of tangential-fired boiler waterwall was corrosion by sulfur contained in the unburned carbon. And the secondary mechanism was $H_2S$ gas corrosion at localized reducing atmosphere. It is required to decrease the air-stage combustion operation in order to mitigate the waterwall tube corrosion. Also stringent coal pulverization quality control and reinforcing work for corrosion susceptible area such as anti-corrosion coatings is required

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.115-121
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• 2000

As the development of industry water quality of river is going to bad because of waste water of an industrial complex and general home agricultural chemicals exhaust of $SO_3$ and CO gas acid rain and so on. Corrosion damage of boiler factory equipment and so forth occur quickly due to using of the polluted water resulting in increasing leak accident. Especially working life of hot water boiler using the polluted water becomes more short and energy loss increases. The cathodic protection method is the most economical and reliable one to prevent corrosion damage of steel structures. Mg-base alloys galvanic anode protection of cathodic protection method is suitable for than application of hot water boiler using water with high specific resistance such as tap water. This paper is studied on the cathodic protection characteristics of how water boiler. In tap water and 0.001mol/$\ell$ NaCl solution the characteristics of anodic polarization of Mg-base alloys galvanic anode and tube material is investigated the measurement of cathodic protection potential according to the time elaspsed is carried out.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.1
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• pp.33-38
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• 2019

Thermal power generation accounts for the highest percentage of domestic power generation, among which coal-fired boiler generation accounts for the highest percentage. Coal boilers generate harmful substances and fine dust during coal combustion and have a serious effect on air pollution. So, fluidized-bed boilers have been introduced as eco-friendly coal boilers. It uses a fluid medium which affect the combustion temperature of coal. Because of it fluidized-bed boilers emit less pollutants than original one. Water-wall tubes play an important role in this fluidized bed boiler. Due to the fluid medium, the wall damage is more severe than the existing boiler. However, there is no quantitative maintenance technique in Korea yet. Remote field eddy current testing is a non-destructive evaluation technique that is often used for inspection of inner and outer wall of tube. it can inspect with non-contact and high speed. However, it is an inspection that proceeds from inside the pipe, and the water-wall tube is not able to enter the interior. In this study, we designed and simulated an external remote field eddy current sensor suitable for water-wall tube of a fluidized - bed boiler using simulations. By obtaining a signal similar to the existing remote field eddy current test, the criteria for the external remote field eddy current sensor design can be presented.