• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1159-1165
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• 2009

In the present study, the flow and heat transfer characteristics of a large plate heat exchanger are investigated numerically. The flow passages are very complicated due to the grooved corrugation patterns of the plate surface so that the detailed mesh and the large amount of the computation time have to be required in the numerical simulation for the conjugate heat transfer analysis. In order to accomplish the efficient and fast analysis of the heat transfer characteristics in the plate heat exchanger, a semimicroscopic method using the porous media model has been investigated numerically. The results showed that the characteristics of the heat transfer and pressure drop, which are respectively presented with Colburn j-factor and Fanning f-factor, are in a good agreement between the detailed mesh and the porous media model. The results of the present study could be applicable to the numerical analysis of entire flow passages in the large plate heat exchanger using porous media treatment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.538-543
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• 2003

Perforated wall has long been employed to control a variety of flow phenomena. It has been, in general, characterized by a porosity of the perforated wall. However, this porosity value does not take account of the number and detailed shape of porous holes, but is defined by only the ratio of the perforated area to total wall surface area. In order to quantify the porous wall effects on the flow control performance, an effective porosity should be known with the detailed flow properties inside the porous holes. In the present study, a theoretical analysis using a small disturbance method is performed to investigate detailed flow information through porous hole and a computational work is also carried out using the two-dimensional, compressible Navier-Stokes equations. Both the results are compared with existing experimental data. The gasdynamical porosity is defined to elucidate the effect of perforated wall.

• 한국유체기계학회 논문집
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• 제20권2호
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• pp.11-16
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• 2017

The accurate prediction of leakage flow through the brush element of brush seal at the steam turbine is important to find optimum design parameters for increasing an efficiency. In this study, CFD analysis method using commercial software FLUENT is proposed to predict leakage through the brush element. Since the brush element has a complex three-dimensional shape with many bristle assemblies, it is difficult to analyze the flow field. Therefore, if the brush element is assumed to be porous medium region, the analysis time can be shortened. Two determination methods of resistance coefficients of the Darcian porous medium equation are suggested. By comparing the 2D and 3D CFD analysis results for the leakage of the brush element using the two resistance coefficient determination methods, the effectiveness of the analysis for the porous medium assumption is proved.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.842-848
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• 2018

Motivated by reducing the uncertainties in quantification of debris bed coolability, this paper reports an experimental study on two-phase flow resistances and interfacial drag in packed porous beds. The experiments are performed on the DEBECO-LT (DEbris BEd COolability-Low Temperature) test facility which is constructed to investigate the adiabatic single and two phase flow in porous beds. The pressure drops are measured when air-water two phase flow passes through the porous beds packed with different size particles, and the effects of interfacial drag are studied especially. The results show that, for two phase flow through the beds packed with small size particles such as 1.5 mm and 2 mm spheres, the contribution of interfacial drag to the pressure drops is weak and ignorable, while the significant effects are conducted on the pressure drops of the beds with bigger size particles like 3 mm and 6 mm spheres, where the interfacial drag in beds with larger particles will result in a descent-ascent tendency in the pressure drop curves along with the fluid velocity, and the effect of interfacial drag should be considered in the debris coolability analysis models for beds with bigger size particles.

• 설비공학논문집
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• 제25권5호
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• pp.269-278
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• 2013

In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate (${\sigma}$) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.195-198
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• 2006

• Coupled systems mechanics
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• 제3권1호
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• pp.27-52
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• 2014

For landfill monitoring and aftercare, long-term prognoses of emission and deformation behaviour are required. Landfills may be considered as heterogeneous porous soil-like structures, in which flow and transport processes of gases and liquids interact with local material degradation and mechanical deformation of the solid skeleton. Therefore, in the framework of continuous porous media mechanics a model is developed that permits the investigation of coupled mechanical, hydraulical and biochemical processes in municipal solid waste landfills.

• 에너지공학
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• 제10권3호
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• pp.266-271
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• 2001

투과 흐름이 있는 수평 다공질 유체층에서 부력에 의하여 발생하는 자연대류 현상을 선형 안정성 이론을 사용하여 해석하였다. 다공질 층에서의 유동 특성을 나타내기 위하여 Dacrcy 법칙을 사용하였다. 선형 안정성 해석 결과를 근거로 자연대류 발생점 근처에서 비선형 해석을 하여 열전달 상관관계를 얻었다. 해석 결과 투과 흐름의 세기가 커짐에 따라 계는 점점 안정해 지고, Darcy-Rayleigh수의 변화에 따른 Nusselt수의 변화는 감소하였다.

• 드라이브 ㆍ 컨트롤
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• 제19권1호
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• pp.62-68
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• 2022

Considering the characteristics of industrial machines that lack vehicle-induced wind, forced convection by a cooling fan is mostly required. Therefore, numerical analysis of an engine room is usually performed to examine the cooling performance in the room. However, most engine rooms consist of a number of parts and components at specific positions, leading to high costs for numerical modeling and simulation. In this paper, a new methodology for three-dimensional computer-assisted design simplification was proposed, especially for the pile of components and parts at the engine room outlet. A porous media model and regression analysis were used to derive a meta-model for imitating the flow rate reduction at the outlet by the pile. The results showed that the fitted model was reasonable considering the coefficient of determination. The final numerical model of the engine room was then used to simulate the velocity distribution by changing the mass flow rate at the outlet. The results showed that both velocity distributions were significantly changed in each case and the meta-model was valid in imitating the flow rate reduction by some piles of components and parts.

• Ocean Systems Engineering
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• 제12권1호
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• pp.63-86
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• 2022

A refined projection-based purely Lagrangian meshfree method is presented towards reliable numerical analysis of fluid flow interactions with saturated/unsaturated porous media of uniform/spatially-varying porosities. The governing equations are reformulated on the basis of two-phase mixture theory with incorporation of volume fraction. These principal equations of mixture are discretized in the context of Incompressible SPH (Smoothed Particle Hydrodynamics) method. Associated with the consideration of governing equations of mixture, a new term arises in the source term of PPE (Poisson Pressure Equation), resulting in modified source term. The linear and nonlinear force terms are included in momentum equation to represent the resistance from porous media. Volume increase of fluid particles are taken into consideration on account of the presence of porous media, and hence multi-resolution ISPH framework is also incorporated. The stability and accuracy of the proposed method are thoroughly examined by reproducing several numerical examples including the interactions between fluid flow and saturated/unsaturated porous media of uniform/spatially-varying porosities. The method shows continuous pressure field, smooth variations of particle volumes and regular distributions of particles at the interface between fluid and porous media.