• Plant Journal
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• v.11 no.1
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• pp.50-57
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• 2015

This study presents prediction of maximum fly ash conveying capacity of fly ash system in a power plant. The mixture ratio and pressure drop characteristics of air-fly ash flow in piping system are not well understood due to the complexity of particle motion mechanism. In this paper, the researcher investigated the optimum mixture ratio when the pressure drop of fly ash conveying system is equal to maximum static pressure of displacement fly ash transport blower and the capacity of fly ash transport according to the optimum mixture ratio by experimenting the fly ash conveying system of domestic D coal thermal power plants, which is currently in operation. The experiment results showed that the maximum fly ash conveying capacity of fly ash system were founded under the condition of maximum air volume 5,040 m3/h, static pressure of trip condition 1,163 mmH2O. In addition, it was predicted maximum mixture ratio of the air-fly ash was 8.66 and maximum capacity of fly ash conveying was 52,600 kg/h under these conditions.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.789-794
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• 2000

The Paper studies the flow and heat transfer characteristics to a jet impinging at different oblique angles, to a plane surface by numerical methods. The flowfield and heat transfer rate associated with the oblique Impingement of an axisymmetric jet are of interest as a result of its presence in numerous technological Problems. For the computation of heat transfer rate, the standard ${\kappa}-{\varepsilon}$ and ${\kappa}-{\varepsilon}-\bar {{\upsilon}'^ 2}$ turbulent model were adapted. The accuracy of the numerical calculations was compared with various experimental data reported in the literature. ${\kappa}-{\varepsilon}-\bar {{\upsilon}'^ 2}$ model showed better agreement with experimental data than standard ${\kappa}-{\varepsilon}$ model in prediction of the turbulent intensity and the heat transfer rate. In the case of computation of flowfield, the study carries on the ${\alpha}=45$ deg, h/D=4.95. The jet Reynolds number based on the nozzle diameter(D), was 48,000. For the computation of heat transfer rate, the Re=20,000, the jet orifice-to-plate spacings(L/D) are 4, 6 and 10, and the angle between the axis of the jet orifice and the plate surface is set at 30, 45, 60, or 90 deg. For the smaller spacings, the near-peak Nusselt numbers are not significantly effected by the initial decreases in the Jet angle. The overall shape of the local Nusselt number x-axis profile is influenced by both the jet orifice-to-plate spacing and the jet angle.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.423-431
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• 2022

In this paper, the results of Planar Motion Mechanism (PMM) test for a 1/15 scaled model of the MARIN Joubert BB2 submarine is dealt with to derive the maneuvering coefficients for surface condition. For the depth of surface navigation, the top of the sail was exposed 0.46 m above the water surface in the model scale, and it corresponds to 6.9 m in the full scale. The resistance and self-propulsion tests were conducted, and the model's self-propulsion point was obtained for 1.328 m/s, which corresponded to 10 knots in the full scale. The maneuvering tests were performed at the model's self-propulsion point, and the maneuvering coefficients were obtained. Based on the maneuvering coefficients, a turning simulation was performed for starboard 30 degree of stern fins. The straight-line stability and control effectiveness in the horizontal plane were analyzed using the maneuvering coefficients and compared with the appropriate range. For the analysis of the neutral fin angle of the X-type stern fin, the stern fin test with drift angles was carried out. As a result, the flow straightening effect at lower and upper parts of the stern fin was discussed.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.405-415
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• 2019

The cracks induced by hydraulic rock splitting technique are formed in the direction parallel to the free plane, which is perpendicular to the minimum principal stress of the ground, or is affected by the pre-existing microcracks. In this study, the hydraulic rock splitting experiments were conducted in which the guide slot was engraved in the direction parallel to the borehole axis on the biotite granite slope, and the hydraulic pressure was injected through the double packer pressure and interval section. The test results show that the cracks along with the guide slots were induced either by the double packer pressurization or the injection of hydraulic pressure into interval section, some cracks extended across the boreholes. Therefore, the hydraulic rock splitting test is expected to control efficiently the induced cracks if the guide slots are engraved in the direction of splitting and a big flow rate is applied.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.379-388
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• 2006

This paper presents a model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. Based on the relationship between shear and bending moment in beams subjected to combined shear and bending, the behavior of a beam is explicitly divided into two base components of the flexural action and the tied arch action. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. The results may confirm the rationale of the proposed behavioral model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.717-726
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• 2016

This study evaluated the effect of aspect ratio of an enclosure with a heated inner circular cylinder on three-dimensional natural convection. The immersed boundary method was used to model the inner circular cylinder based on the finite volume method. The Rayleigh number was varied between $10^5$ and $10^6$, and the Prandtl number was maintained at 0.7. The aspect ratio of the three-dimensional enclosure was changed in steps of 1 within a range of 1-4 by increasing the width of the enclosure. In this study, the flow and thermal fields in the enclosure reached the steady state, and showed a mirror-symmetric pattern with respect to the center plane (x=0). In addition, the surface-averaged Nusselt number of the inner circular cylinder increased, while the total surface-averaged Nusselt number of the enclosure walls decreased with increase in the aspect ratio of the enclosure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.304-320
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• 1996

A multiple production .epsilon. equation model was developed in the low Reynolds number $\kappa$-$\varepsilon$ model with the aids of DNS data. We derived the model theoretically and avoided the use of empirical correlations as much as possible in order for the model to have generality in the prediction of complex turbulent flow. Unavoidable model constants were, however, optimized with the aids of DNS data. All the production and dissipation models in the $\varepsilon$ equation were modified with damping functions to satisfy the wall limiting behavior. A new $f_{\mu}$ function, turbulent diffusion and pressure diffusion model for the k and .epsilon. equations were also proposed to satisfy the wall limiting behavior. By, computational investigation on the plane channel flows, we found that the multiple production model for .epsilon. equation could improve the near wall turbulence behavior compared with the standard production model without the complicated empirical modification. Satisfication of the wall limiting conditions for each turbulence model term was found to be most important for the accurate prediction of near wall turbulence behaviors.

• Plant Journal
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• v.16 no.3
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• pp.42-46
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• 2020

In the large LNG process in FLNG or FSRU, sudden temperature drops of the steel in the event of LNG leaks may cause brittle fracture of the structure. In this paper, we investigate the principle and process of forming a cryogenic fluid on a steel plate through a cryogenic spillage experiment, and analyze the correlation of the temperature distribution of the steel plate according to the distance from the nozzle and exposure time. Two types of cryogenic fluids were used: LN2 and LNG. The cyogenic liquid was released on the steel plate at 1.6L/min for LN2 and 1.5L/min for LNG. For the steel, DH was used and the temperature was measured at 10 points in total. The Leidenfrost effect was observed on the steel plate, and the temperature distribution of the steel was varied according the flow path and the heat of evaporation of the fluid.

• Plant Journal
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• v.14 no.3
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• pp.35-41
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• 2018

Considering the recent government policy toward North Korea and situation of power facilities in North Korea, it will be necessary to prepare for the consumption of the anthracite coal from Korea in coal-fired power plants. In this study, the anthracite co-fired tests in 500 MW thermal power plants were conducted with varying the main operation conditions, such as anthracite injection position in the boiler, coal fineness and combustion air flow, to investigate the effects on the generation of unburned carbon. It was confirmed that the generation of unburned carbon was remarkably reduced when the anthracite coal was injected into the boiler low burner with a relatively long residence time in the main combustion region, and that the increase of the coal fineness proportional to the combustion reaction surface area also reduces the generation of unburned carbon. An increase in the combustion air flow, which increase the combustion reactivity, also contributes to the reduction of unburned carbon. It is possible to maintain the unburned carbon generation below 5 % of the ash recycling quality by controlling the above operating conditions for the given mixing rate of anthracite, and the priority of changing the operating conditions within the test range is the highest for anthracite coal injection position.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.99-107
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• 1993

In this study, material nonlinear finite element program is developed to analyze reinforced concrete shell of arbitrary geometry considering tension stiffening effects. This study is capable of tracing the load-deformation response and crack propagation, as well as determining the internal concrete and steel stresses through the elastic, inelastic and ultimate ranges in one continuous computer analysis. The cracked shear retention factor is introduced to estimate the effective shear modulus including aggregate interlock and dowel action. The concrete is assumed to be brittle in tension and elasto-plastic in compression. The Drucker-Prager yield criterion and the associated flow rule are adopted to govern the plastic behavior of the concrete. The reinforcing bars are considered as a steel layer of equivalent thickness. A layered isoparametric flat finite element considering the coupling effect between the in-plane and the bending action was developed. Mindlin plate theory taking account of transverse shear deformation was used. An incremental tangential stiffness method is used to obtain a numerical solution. Numerical examples about reinforced concrete shell are presented. Validity of this method is studied by comparing with the experimential results of Hedgren and the numerical analysis of Lin.