• Steel and Composite Structures
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• v.29 no.2
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• pp.151-159
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• 2018

In order to reduce the deformation and delay the local buckling of concrete filled steel tube (CFST) columns, strengthening the structures with stiffeners is an effective method. In this paper, a new stiffening method with inclined stiffeners was used to investigate the behaviors of short CFST columns under axial compression. Besides, a three-dimensional nonlinear finite element (FE) model was applied to simulate the mechanical performances, including the total deformation, local buckling, and stress-strain relationship. Revised constitutive models of stiffened steel tube and confined concrete are proposed. A good agreement was achieved between the test and FE results. Furthermore, the calculated results of load capacity by using a simplified method also show a good correlation with experimental data.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.68-74
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• 2015

Time domain response analysis for vibro-impact nonlinear behavior of multi-span tube with loose supports was performed using commercial FEA code and user subroutine. Support geometry of multi-span tube with a finite gap is realistically modeled by analytical rigid surface. Model of hydrodynamic force is based on the Qusai-steady model which accounts for the inclined angle of relative flow velocity and time delay between flow force and resulting tube motion. During tube vibration from flow loading, impact and friction at the support location is simulated using commercial FEA code with master slave contact algorithm. Analysis results has reasonable agreement with those of references and test experience. Plan of further refinement of analysis model and future test verification is briefly introduced.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.35-40
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• 2011

If a plugged tube in a steam generator is broken, it may damage nearby intact tubes. To prevent this damage, it is recommended that a stabilizer is installed into the plugged tube. However, the installation cost of a stabilizer is very high. So studies are required to determine the conditions on which the installation is necessary. For this purpose static loads and dynamic loads applied on a tube should be known to estimate the residual strength and remaining fatigue and wear life of a plugged tube. Two-dimensional and three-dimensional computational fluid dynamics (CFD) analyses are performed to obtain the drag coefficient for cross flow to a tube. Using the obtained drag coefficient, the static load can be estimated and the residual strength of a plugged tube can be calculated. An inclined flow problem is also analyzed and the vertical and horizontal forces are obtained and discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.9
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• pp.516-521
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• 2013

In the present study, the performances of a fin-tube evaporator and three PF evaporators for a heat pump dryer were experimentally investigated. Among the tested evaporators, the PF3 type evaporator showed the highest values of heat transfer capacity and dehumidification performance, while the fin-tube evaporator had the lowest values. PF3 showed better performance compared to PF1 and PF2, due to the large pin pitch, which leads to more draining for dehumidified water. Also, the $45^{\circ}$ inclined PF evaporator presented better performance than that of the $90^{\circ}$ inclined PF evaporator, owing to its easier draining characteristics. The effect of air velocity was revealed to be quite large. When the air velocity increased by 20%, the heat transfer capacity and dehumidification performance increased 43%/11%, 48%/13% and 54%/23% for PF1, PF2 and PF3, respectively.

• Advances in nano research
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• v.12 no.3
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• pp.253-261
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• 2022

Numerical modelling of an integrated Carbon NanoTube (CNT) membrane is only achievable if probable deformations and realistic alterations from a perfect CNT membrane are taken into account. Considering the possible forms of CNTs, bending is one of the most probable deformations in these high aspect ratio nanostructures. Hence, investigation of effect associated with bent CNTs are of great interest. In the present study, molecular dynamics simulation is utilized to investigate fluid flow dynamics in deformed CNT membranes, specifically when the tube cross section is not affected. Bending in armchair (5,5) CNT was simulated using Tersoff potential, prior to flow rate investigation. Also, to study effect of inclined entry of the CNT to the membrane wall, argon flow through generated inclined CNT membranes is examined. The results show significant variation in both cases, which can be interpreted as counter-intuitive, since the cross section of the CNT was not deformed in either case. The distribution of fluid-fluid and fluid-wall interaction potential is investigated to explain the anomalous behavior of the flow rate versus bending angle.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.435-435
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• 2010

A inclined slot-excited plasma source is newly designed and constructed for higher flux HNB(Hyperthermal Neutral Beam) generation. The present source is different from the vertical SLAN(SLot ANtenna) sources [1] in two aspects. One is that the slots are inclined, and the other is that the magnetic field is configured to a cusp type. These modifications are intended to make the source plasma operated in sub-milli-torr pressure regime and as thin as possible, both of which is to get higher HNB flux by decreasing the re-ionization rate of the reflected atoms from the neutralizer [2]. The plasma is generated in a quartz tube of internal diameter 170 mm enclosed in a aluminum application chamber of larger diameter 250 mm. The microwave power is fed to the plasma chamber by 8 inclined slots cut into the application chamber wall. The slots are coupled the chamber to a WR280 waveguide wound around it to form a ring resonator. In order to make two slots $\lambda_g/2$ apart in phase, the adjacent slots are rotated in opposite directions. The rotation angle of the slots are set to $60^{\circ}$ from the chamber axis. Between the quartz chamber and the aluminum cylindrical chamber 8 NdFeB magnets are equally spaced and fixed to form the cusp magnetic field confinement and ECR (Electron Cyclotron Resonance) field. In this presentation, the magnetic and electromagnetic simulations, and the measured plasma parameters are given for both the inclined and the vertical slot-excited plasma sources. We also discuss how the sources can be tailored to suit better-performing HNB sources.

• Nuclear Engineering and Technology
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• v.31 no.1
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• pp.29-48
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• 1999

Local two-phase flow parameters of subcooled flow boiling in inclined annulus were measured to investigate the effect of inclination on the internal flow structure. Two-conductivity probe technique was applied to measure local gas phasic parameters, including void fraction, vapor bubble frequency, chord length, vapor bubble velocity and interfacial area concentration. Local liquid velocity was measured by Pilot tube. Experiments were conducted for three angles of inclination; 0$^{\circ}$(vertical), 30$^{\circ}$, 60$^{\circ}$. The system pressure was maintained at atmospheric pressure. The range of average void fraction was up to 10% and the average liquid superficial velocities were less than 1.3 m/sec. The results of experiments showed that the distributions of two-phase How parameters were influenced by the angle of channel inclination. Especially, the void fraction and chord length distributions were strongly affected by the increase of inclination angle, and flow pattern transition to slug flow was observed depending on the How conditions. The profiles of vapor velocity, liquid velocity and interfacial area concentration were found to be affected by the non-symmetric bubble size distribution in inclined channel. Using the measured distributions of local phasic parameters, an analysis for predicting average void fraction was performed based on the drift flux model and flowing volumetric concentration. And it was demonstrated that the average void fraction can be more appropriately presented in terms of flowing volumetric concentration.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.209-219
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• 2006

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Different shock tube fill pressures have various inflow conditions. $15^{\circ}$ inclined hydrogen fuel injection is located before the cavity. Oblique shock is generated at the trailing edge of the cavity and reflects off the top and bottom wall. For non-reacting flow, static pressures in low equivalence ratio are similar to those in no fuel injection. As equivalence ratio is increased, static pressures are increased in the duct. In the similar equivalence ratio, static pressures are increased when total enthalpy is decreased. For reacting flow, the flame is occurred near the cavity. The combustion is weak locally in the middle of the duct. The up and down pressure distribution in the duct means that the supersonic combustion is generated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.8
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• pp.527-533
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• 2016

A new empirical correlation was developed to identify the effect of an inclination angle on pool boiling heat transfer coefficient of a tube submerged in the saturated water at atmospheric pressure. Through the experiments and the survey of published results 431 data points were obtained and the nonlinear least square method was used as a regression technique. The heat flux of the tube($0{\sim}120kW/m^2$), inclination angle($0^{\circ}{\sim}90^{\circ}$), and the length divided by the diameter of a tube(18~42.52) were selected as major parameters. The newly developed correlation well predicts the experimental data within ${\pm}18%$, with some exceptions.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.76-76
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• 2004