• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1184-1189
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• 2004

Coking process is the thermal decomposition of bituminous coal with final temperature of about $900^{\circ}C$ Because coke plays important roles in ironmaking process in a blast furnace it's essential for developing modeling of coke oven. In this study, An unsteady 2-dimesional model is proposed to simulate coking process in a coke oven. In this model, gas and solid phase are assumed homogeneous continnum and solid bed is assumed as porous media . The model contains governing equations for the solid phase and the gas phase. Complicated phenomena such as swelling, softening, resolidification and shrinkage are neglected and mass loss by drying and devolatilization is reflected by generation of internal pores. Drying, devolatilization, heat transfer and generation of internal pores are also reflected in source terms. Calulated results are compared with experimental data

• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.161-168
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• 2001

Sintering bed of iron ore in the steel making process is one of typical applications of solid fuel bed, which has relatively uniform progress of fuel and simple processes of combustion. The sintering bed was modelled as an unsteady one-dimensional progress of fuel layer containing the two phases of solid and gas. Cokes added to the raw mix of which the amount is about 3.5% of the total weight was assumed to form a single particle with other components. In the early predition results presented in this paper, the flame propagation within the bed was not sustained after the top surface of the bed was ignited with hot gas. It suggests that the model should be extended to consider the multiple solid phase, which can treat the ore particles and the coke particles separately.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.253-255
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• 2012

This study has numerically investigated the combustion processes in the bilayer porous media. To account for the velocity transition and diffusion influenced by solid matrix, porosity effects are included in the governing equations. Heat transfer coefficient is calculated by Nusselt number to reflect the effect of gas velocity, pore diameter, and material properties. Numerical results indicate that the present approach is capable of the essential features of the premixed combustion in the porous burner, in terms of the precised flame structure, pollutant formation, and flame stabilization. It is also found that heat transferred from the downstream flame zone is conducted to the upstream flame region through the solid matrix and the preheated mixture. By increasing the inlet velocity, the solid temperature of upstream is cooling down.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1177-1184
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• 2011

Gas-to-Solid (GTS) technology is composed of three stages: hydrate production, transportation, and regasification. For efficient operation of regasification plants, it is crucial to predict the temperature and flow rate of hot water necessary to dissociate the hydrate pellets. Dissociated gas escaping from the pellet surface, when in contact with hot water, will alter the flow field and consequently alter the heat transfer rate. Methane hydrate pellet dissociation characteristics in low- to moderatetemperature water were investigated by taking images of the changes in the hydrate pellets' shapes in a pressurized reactor and measuring the total time required for complete melting of the pellets. The effects of water temperature, hydrate conversion rate, and flow speed on the dissociation completion time were also investigated. Bubbling gas released from the pellet surface induced a secondary flow that enhanced the heat transfer rate and thus decreased the dissociation time. It was also found that a considerable flow rate was needed to significantly decrease the dissociation time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2404-2412
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• 1994

A mathematical model has been developed for predicting kinematic, thermal, and solidification histories of atomized droplets during flight. Liquid droplet convective cooling, recalescence, equilibrium-state solidification, and solid-phase cooling were taken into account in the analysis of the solidification process. The spherical shell model was adopted where the heterogeneous nucleation is initiated from the whole surface of a droplet. The growth rate of the solid-liquid interface was determined from the theory of crystal growth kinetics with undercooling caused by the rapid solidification. The solid fraction after recalescence was obtained by using the integral method. The thermal responses of atomized droplets to gas velocity, particle size variation, and degree of undercooling were investigated through the parametric studies. It is possible to evaluate the solid fraction of the droplet according to flight distance and time in terms of a dimensionless parameter derived from the overall energy balance of the system. It is also found that the solid fraction at the end of recalescence is not dependent on the droplet size and nozzle exit velocity but on the degree of subcooling.

• Journal of Korea Foundry Society
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• v.13 no.5
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• pp.462-475
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• 1993

A numerical analysis on the microstructural evolutions of microcellular and cellular ${\alpha}-aluminum$ phase in the gas-atomized Al-8wt. pct droplets was represented. The 2-dimensional non-Newtonian heat transfer and the dendritic growth theory in the undercooled melt were combined under the assumptions of a point nucleation on droplet surface and the macroscopically smooth solid-liquid interface enveloping the cell tips. It reproduced the main characteristic features of the reported microstructures quite well. It predicted a considerable volume fraction of segregation-free region in a droplet smaller than $l0{\mu}m$ if an initial undercooling larger than 100K is given. The volume fractions of the microcellular region($g_A$) and the sum of the microcellular and cellular region($g_a$) were predicted as functions of the heat transfer coefficient, h and initial undercooling, ${\triangle}T$. It was shown that $g_A$ and $g_a$, in the typical gas-atomization processes with $h=0.1-1.0W/cm^2K$, are dominated by ${\triangle}T$ and h, respectively, but for h larger than $4.0W/cm^2K$, a fully microcellular structure can be obtained irrespective of the initial undercooling.

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.9-23
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• 2013

A rotary kiln furnace is one of the most widely used gas-solid reactors in the industrial field. Although the rotary kiln is a versatile system and has different size, approach to the reactor modeling can be generalized in terms of flow motion of the solid and gas phases, heat transfer, and chemical reactions on purpose. In this paper, starting from a zero-dimensional model and extending to higher dimension and comprehensive models, overall procedure of the design development of rotary kiln reactors and considerations are presented. The approaches to performance analysis of the reactors are introduced and examples of application cases are presented.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.644-651
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• 2011

Storing hydrogen in solid state hydride is one of the best promising methods for the future hydrogen economy. The total performance of such systems depends on the rate at which the amount of mass and heat migration is supplied to solid hydride. Therefore, an accurate modeling of the heat and mass transfer is of prime importance in optimizing the design of such systems. In this work, Hydrogen storage in Pt-CNTs hydrogen reactor has been intensively investigated by solving 2 dimensional mathematical models. Using a CFD computer software, systematic studies have been performed to elucidate the effect of heat and mass transfer during hydrogen charging periods. It was revealed that the optimized design of hydrogen storage vessel can prevent the increase of system temperature and the charging time due to the convective cooling effects inside the vessels at even high charging pressure. Because none has reported the critical issues of heat and mass transfer for CNT based hydrogen storage system, this work can support the first insight of the optimal design for solid state hydrogen storage system based on CNT in the near future.

• Journal of the Korean Society of Combustion
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• v.7 no.3
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• pp.23-31
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• 2002

Processes in an iron ore sintering bed can characterized as a relatively uniform progress of fuel, cokes combustion and complicated physical change of solid particles. The sintering bed was modelled as an unsteady one-dimensional progress of the fuel layer, containing two phases: solid and gas. Coke added to the raw mix, of which the amount is about 3.5% of the total weight, was assumed to form a single particle with other components. Numerical simulations of the condition in the iron ore sintering bed were performed for various parameters: moisture contents, cokes contents and air suction rates, along with the various particle diameters of the solid for sensitivity analysis. Calculation results showed that the influence of these parameters on the bed condition should be carefully evaluated, in order to achieve self-sustaining combustion without high temperature section. The model should be extended to consider the bed structural change and multiple solid phase, which could treat the inerts and fuel particles separately.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.171-178
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• 2002

Numerical simulations of the condition in the iron ore sintering bed are performed for various parameters. The sintering bed is modelled as an unsteady one-dimensional progress of solid material, containing cokes and iron ore. Bed temperature, solid mass and gas species distributions are predicted for various parameters of moisture contents, cokes contents and air suction rates, along with the various particle diameters of the solid for sensitivity analysis. Calculation results show that influences of these parameters on the bed condition should be carefully evaluated for achievement of the self-sustaining combustion without the high temperature section, which can cause the excessive melting in the bed. It suggests that the model should be extended to consider the bed structural change and multiple solid phase, which can treat the inerts and fuel particles separately.