• 한국연소학회:학술대회논문집
• /
• 2002.11a
• /
• pp.157-163
• /
• 2002

Using the CFD method, we investigated the combustion characteristics of grate-rotary kiln incinerator through the residence time, path line of flow and distributions of temperature and CO mass fraction according to the shape of mixing chamber and the existence and nonexistence of baffle at the exit of bypass duct. The results show that the now mixing and residence time could be variable according to the shape of mixing chamber and baffle, and we could know the temperature in the mixing chamber could increase too high if the combustion process on the grate retarded.

• Journal of the Korean Vacuum Society
• /
• v.12 no.S1
• /
• pp.74-78
• /
• 2003

In this paper, we studied, by numerical calculation, a system, which was composed of metal-film and metal-substrate irradiated by IPIB with beam ion energy 250 keV, current density 10 to 250 A/$\textrm{cm}^2$. While the IPIB irradiation was going on, an induced effect named mixing occurred. In this case, metal-film and part of metal-substrate melted and mixed. The mixing state was kept as it was in melting phase due to the fast cooling rate. Our works were simulating the heating and cooling process via our STEIPIB program and tried to find proper parameters for a specific film-substrate system, 500 nmtitanium film coated on aluminum, to get best mixing results. The parameters calculated for such Ti-Al system were compared with the experimental results and were in good accordance to the experimental results.

• 유체기계공업학회:학술대회논문집
• /
• 2003.12a
• /
• pp.101-106
• /
• 2003

In this work, mixing phenomena in the mixing chamber of a ultrasonic micromixer are analyzed through an analytical approach. A simplified 2-dimensional model for the ultrasonic micromixer is presented. Analytical solutions for fluid flow induced by ultrasonic waves are obtained through successive approximations method. From simulation results on thermal diffusion in the mixing chamber, effects of relative location, size, and vibration frequency of a piezoelectric material and aspect ratio of the mixing chamber on mixing performance of the ultrasonic micromixer are investigated. Finally, design guidelines for the ultrasonic micromixer are suggested based on the parametric study.

• 유체기계공업학회:학술대회논문집
• /
• 2003.12a
• /
• pp.231-237
• /
• 2003

A numerical study has been conducted to investigate the effect of an inlet flow pulsation on mixing of two solutions with different concentrations in a micro conduit. We treat an unsteady, incompressible and two-dimensional flow through a micro conduit by adopting the momentum equations with the electrostatic force due to streaming current and the concentration equation. The feasibility of the inlet flow pulsation to enhance the mixing process inside the micro conduit is carefully examined by varying the inlet pulsation frequency. When a low-frequency pulsation is induced at the inlet, the interface between two solutions with different concentrations becomes wavy, which results in mixing enhancement. As the pulsation frequency increases, the waviness of the interface becomes meager, and the concentration gradients at the interface approach the value for the non-pulsating steady flow.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.6
• /
• pp.29-37
• /
• 2014

Non-Newtonian fluid mechanics takes charge of an important role in the oil industries. Especially in the oil well drilling process, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. The purpose of this study is to examine the effect of fluid mud rheological properties to predict different characteristics of non-Newtonian fluid in the mud mixing tank on offshore drilling platforms. In this paper, ANSYS fluent package was used for the simulation to solve the hydrodynamic force and to evaluate mud mixing time. Prediction of the power consumption and the pumping effectiveness has been presented with different operating fluid models as Newtonian and non-Newtonian fluid. The comparison between Newtonain mud model and non-Newtonian mud model is confirmed by the CFD simulation method of drilling mud mixing tank. The results present useful information for the design of the drilling mud mixing tanks and provide some guidance on the use of CFD tool for such non-Newtonian fluid flow.

• Advances in concrete construction
• /
• v.17 no.5
• /
• pp.285-292
• /
• 2024

In order to improve the mixing effect of slurry-foam during the preparation of foam concrete, this study takes an SK static mixer as the mixing device, establishes a three-dimensional physical model and a theoretical calculation model, and numerically simulates the effects of different parameters such as foam inlet angle and pipe inner diameter on the mixing of cement slurry and foam under the given boundary conditions, so as to optimize the structure of this mixing device. The results show that when the pipe diameter of the mixer is larger than 60 mm, the phenomenon of backflow occurs in the pipe, which affects the mixing effect. The smaller the pipe diameter, the shorter the distance required to stabilize the cross-sectional average density and density uniformity index. When the foam inlet angle is different, the average density and density uniformity index of the radial cross-section have the same rule of change along the length of the pipeline, and all of them tend to stabilize gradually. At Y = 0.5 m, the average density basically stabilizes at 964 kg/m³ and remains stable until the outlet. At Y = 0.6 m, the density uniformity index basically stabilizes above 0.995 and remains stable until the outlet. Except for the foam inlet position (Y = 0.04 m), the foam inlet angle has little effect on the cross-sectional average density and density uniformity index. Under the boundary conditions given in this study, a pipe diameter of 40 mm, a foam inlet angle of 90°, and a pipe length of 700 mm are the optimal geometries for the preparation of homogeneous foam concrete with a density of 964 kg/m³ in this static mixer.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.12 s.255
• /
• pp.1642-1648
• /
• 2006

This paper describes enhancement of the mixing efficiency of a multilamination micro mixer by adding a number of recirculation zones downstream of the mixing zone. Numerical simulation was employed to estimate the mixing efficiency and the pressure drop under various conditions. Numerical results indicated that recirculation micro mixer brought about not only the increase of the mixing efficiency but also the decrease of the pressure drop. Micro mixers were fabricated using photosensitive glass by anisotropic wet etching technique. The width and height of the micro channel were $150{\mu}m$ and $500{\mu}m$, respectively. The performance of micro mixer was measured using color intensity variation of the fluid. Except for extremely low Re below 40, the recirculation micro mixer of the present study showed improved mixing. And the enhancement of the mixing increased as Re rose. When Re increased beyond 400, more than 90% of the mixing was observed in the experiment.

• Journal of computational fluids engineering
• /
• v.20 no.1
• /
• pp.84-91
• /
• 2015

SMART adopts, very unique facility, an FMHA to enhance the thermal and flow mixing capability in abnormal conditions of some steam generators or reactor coolant pumps. The FMHA is important for enhancing thermal mixing of the core inlet flow during a transient and even during accidents, and thus it is essential that the thermal mixing characteristics of flow of the FMHA be understood. Investigations for the mixing characteristics of the FMHA had been performed by using experimental and CFD methods in KAERI. In this study, the temperature distribution at the core inlet region is investigated for several abnormal conditions of steam generators using the commercial code, FLUENT 12. Simulations are carried out with two kinds of FMHA shapes, different mesh resolutions, turbulence models, and steam generator conditions. The CFD results show that the temperature deviation at the core inlet reduces greatly for all turbulence models and steam generator conditions tested here, and the effect of mesh refinement on the temperature distribution at the core inlet is negligible. Even though the uniformity of FMHA outlet hole flow increases the thermal mixing, the temperature deviation at the core inlet is within an acceptable range. We numerically confirmed that the FMHA applied in SMART has an excellent mixing capability and all simulation cases tested here satisfies the design requirement for FMHA thermal mixing capability.

• Journal of Environmental Science International
• /
• v.11 no.6
• /
• pp.543-551
• /
• 2002

A Numerical simulation on the thermal flow performance was carried out to propose the incinerator type for the domestic refuses and to investigate the design factor and operating conditions. The SSTI(Standard Stoker Type Incinerator) proposed in this study was modified from the type with central f)ow. It has the characteristics of good mixing between refuse and hot combustion gas in primary combustion chamber and between unburned gas inflowing and secondary air jet in secondary chamber. By predictive results, the SSTI was no recirculation zone in secondary chamber so that mixing time was increased with high residence time. It has good characteristics of combustion and low emission. Parametric screening studies have been understood with phenomenon of combustion in incinerator.

• Journal of the Korean Society of Combustion
• /
• v.6 no.2
• /
• pp.23-28
• /
• 2001

In the present work, the effect of PDF selection and intermittency on the result of the numerical simulation are examined by the simulation of a turbulent methane-air jet diffusion flame. As to the PDFs, beta-function and clipped Gaussian are considered. Results for the pure mixing jet are compared with experimental results. Then, the turbulent flame is calculated for the same conditions and the results obtained for the several models are compared. It is found that the clipped Gaussian distribution coupled with consideration of intermittency recovers the experimental data very well. As to the reacting flow results, the main overall properties of the turbulent jet diffusion flame such as maximum flame temperature are less affected by the choice of the PDF. Flame height and NO emissions, on the contrary, appear to be significantly influenced.