• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.58-67
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• 1996

This paper describes some computational results of various energy and environmental systems using Patankar's SIMPLE method. The specific topics handled in this study are jet bubbling reactor for flue gas desulfurization, cyclone-type afterburner for incineration, 200m tall stack for 500 MW electric power generation, double skin and heat storage systems of building energy saving for the utilization of solar heating, finally turbulent combustion systems with liquid droplet or pulverized coal particle. A control-volume based finite-difference method with the power-law scheme is employed for discretization. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, that is, SIMPLEC. Reynolds stresses are closed using the standard $k-{\varepsilon}$ and RNG $k-{\varepsilon}$ models. Two-phase turbulent combustion of liquid drop or pulverized coal particle is modeled using locally-homogeneous, gas-phase, eddy breakup model. However simple approximate models are incorporated for the modeling of the second phase slip and retardation of ignition without consideration of any detailed particle behavior. Some important results are presented and discussed in a brief note. Especially, in order to make uniform exit flow for the jet bubbling reactor, a well-designed structure of distributor is needed. Further, the aspect ratio in the double skin system appears to be one of important factors to give rise to the visible change of the induced air flow rate. The computational tool employed in this study, in general, appears as a viable method for the design of various engineering system of interest.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1487-1503
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• 2019

The methods and performance of a pin-level nuclear reactor core thermal-hydraulics (T/H) code ESCOT employing the drift-flux model are presented. This code aims at providing an accurate yet fast core thermal-hydraulics solution capability to high-fidelity multiphysics core analysis systems targeting massively parallel computing platforms. The four equation drift-flux model is adopted for two-phase calculations, and numerical solutions are obtained by applying the Finite Volume Method (FVM) and the Semi-Implicit Method for Pressure-Linked Equation (SIMPLE)-like algorithm in a staggered grid system. Constitutive models involving turbulent mixing, pressure drop, and vapor generation are employed to simulate key phenomena in subchannel-scale analyses. ESCOT is parallelized by a domain decomposition scheme that involves both radial and axial decomposition to enable highly parallelized execution. The ESCOT solutions are validated through the applications to various experiments which include CNEN $4{\times}4$, Weiss et al. two assemblies, PNNL $2{\times}6$, RPI $2{\times}2$ air-water, and PSBT covering single/two-phase and unheated/heated conditions. The parameters of interest for validation include various flow characteristics such as turbulent mixing, spacer grid pressure drop, cross-flow, reverse flow, buoyancy effect, void drift, and bubble generation. For all the validation tests, ESCOT shows good agreements with measured data in the extent comparable to those of other subchannel-scale codes: COBRA-TF, MATRA and/or CUPID. The execution performance is examined with a mini-sized whole core consisting of 89 fuel assemblies and for an OPR1000 core. It turns out that it is about 1.5 times faster than a subchannel code based on the two-fluid three field model and the axial domain decomposition scheme works as well as the radial one yielding a steady-state solution for the OPR1000 core within 30 s with 104 processors.

• 대한환경공학회지
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• 제27권3호
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• pp.286-292
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• 2005

본 연구는 향후 산업적으로 질소산화물 규제가 중요한 문제로 대두될 만한 산업용 보일러를 대상으로 수행하였다. 일반적으로 SNCR 방법의 산업용 보일러로의 적용은 혼합을 위한 충분한 체류시간을 제공하지 못한다는 점에서 적합하지 않은 것으로 알려져 있다. 본 연구의 목적은 SNCR 장치의 산업용 보일러 적용가능성을 조사하기 위한 것이다. 구체적으로 연료로 중유를 사용하는 시간당 스팀 발생량 40톤 규모의 산업용 보일러를 연구 대상으로 하였다. 사업용 보일러의 수치 해석을 위한 3-D 직교좌표계 프로그램에는 난류 유동, 난류 연소반응, NOx의 생성과 환원제와의 반응을 통한 소멸반응 등을 포함하고 있다. 또한 개발된 코드에는 Lagrangian 방법에 의한 입자궤적 프로그램이 포함되어 있고, 주입구에서 접선방향으로의 선회효과를 계산에 의해 고려하였다. 선회버너 효과를 고려한 결과 단화염이 생성되었으며 NOx 환원반응에 적합한 온도 영역의 증가로 인해 NOx 제거효율도 향상되었다. 실험결과와의 비교를 통하여 프로그램을 검증하였으며, 계산결과 혼합용 공기 주입을 통한 환원제와의 혼합 향상을 통해서 SNCR 방법의 산업용 보일러 적용가능성을 확인하였다.