• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.75-77
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• 2011

Thermofluid flow analysis is major subject in most computational fluid dynamics applications. Accompanying convective and conductive heat transport phenomena, radiation plays an important role in high temperature operating systems. Cares in which the radiation dominates are found in such systems as boilers, furnaces, rocket engines, etc. In this paper the finite-volume method (FVM) are employed to simulate two-dimensional radiation problems in concentric and eccentric horizontal cylindrical annuli with general body-fitted coordinates. In that case the simplest and intuitive remedies are proposed for mitigation of ray effect.

• 한국기계가공학회지
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• 제2권4호
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• pp.82-87
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• 2003

Flow angle with Swirl in a horizontal circular tube and a cylindrical annuli were experimentally studied for its visualization. This present investigation deals with flow angle, flow visualization studies and vortex core by using oil smoke and a hot wire anemometer for Re = 40,000 and 50000 at X/D = 41, 59 and 71 in a horizontal circular tube. In the swirl air flow, a vortex core was formed at high swirl intensity along the test tube. The flow angle and the vortex core depended on the swirl intensity along the test tube. The results of flow angles with swirl measured by flow visualization and hot wire reasonably agree with those of Sparrow One of the primary objectives of this research was to measure the flow angle with swirl in a cylindrical annuli along the test tube for different Reynolds numbers. The Reynolds number for these measurements ranged from 60,000 to 100,000 with L/D = a to 4.

• 대한기계학회논문집B
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• 제22권12호
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• pp.1796-1804
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• 1998

A numerical investigation has been performed to discuss the radiation-affected steady-laminar natural convection induced by a hot inner cylinder under a large temperature difference in the annuli filled with a gray gas. To examine the effects of thermal radiation on thermo-fluid dynamic behaviors in the eccentric geometry, the generalized body-fitted coordinate system is introduced while the finite volume method (FVM) is used for solving the radiative transport equation. After validating the numerical results for the case without radiation, the detailed radiation effect has been discussed. Based on the results of this study, when there exists a large temperature difference between two cylinders, the existence of radiatively participating medium is found to incur a distinct difference in fluid dynamic as well as thermal behavior.

• 동력기계공학회지
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• 제1권1호
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• pp.61-69
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• 1997

본 연구는 동심환형관에서 거칠기가 없이 매끈한 경우, 내측벽에 만, 외측벽에 만, 그리고 양측 모두에 거칠기가 있는 4경우에 대해 직경비가 0.26, 0.39, 그리고 0.56일 때 벽면에 설치된 거칠기 위치들이 난류유동장에 미치는 효과를 실험적으로 조사하고자 한다. 최대속도와 전단응력이 0인 지점들, 시간평균속도의 구배들, 그리고 와확산계수들을 X형 열선풍속계와 이중 피토튜브를 사용하여 측정하였다. 본 연구를 통하여 동심환형관에 설치된 거칠기들이 난류유동에 미치는 효과에 대한 정량적자료를 제시할 수 있었다.

• 설비공학논문집
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• 제13권9호
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• pp.803-809
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• 2001

The present paper presents the experimental results of pressure drip of water flow in annuli with spirally corrugated inner tubes in the turbulent flow regime. To understand the underlying physical phenomena responsible for heat transfer enhancement, pressure drop data documented elsewhere are combined to compare with those obtained from the present experiment for the Reynolds numbers of 1,000 to 8,000. Friction factors were found to be functions of trough depth, pitch and angle, and the annulus radius ratio. Friction factor increases in the spirally fluted tubes were larger than those in the corrugated tubes.

• 설비공학논문집
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• 제18권4호
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• pp.370-376
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• 2006

The paper concerns an experimental study of fully developed laminar flow of a Newtonian and non-Newtonian liquid in concentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured for Newtonian fluid, water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose (CMC) and 5% bentonite solutions, when the inner cylinder rotates at the speed of $0{\sim}500$ rpm. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated. And the new correlations among the skin friction coefficient, the Reynolds number and the Rossby number are presented with reasonable limits of accuracy in laminar flow regime.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.328-335
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• 1988

Natural convection in annuli between the horizontal and vertical concentric cylinders for ratio of the inner to the outer radius, $R_1$=0.85, 0.35 has been studied by the numerical analysis. Governing equations are numerically sloved by means of Successive over-relaxation methods. It is found that maximum local Nusselt number, $Nu_{1.max}$ at the inner cylinder and $Nu_{2.max}$ at the outer cylinder for $R_2$=0.35 have maxima at ${\phi}=0^{\circ}$, ${\phi}=180^{\circ}$ ${\xi}=0.4$, 1.6 for horizontal cylinder and at bottom, top for vertical cylinder, respectively. In the present study, mean Nusselt numbers at the vertical cylinder increased more than that at the horizontal cylinder by about 64% for $R_1$=0.35.

• 한국초전도ㆍ저온공학회논문지
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• 제10권4호
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• pp.33-37
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• 2008

The main objective of this study is to identify the pressure drop characteristics of coolant flow passages of 154kV/1GVA High Temperature Superconducting (HTS) power cable, experimentally. The passages were consisted of two parts, the one is the circular path with spiral ribs in the core to cool the cable conductor layer and the other is annular path with spirally corrugated outer wall to cool the shield layer. Thus the experiments to acquire the pressure drop data were performed with two types of circular spiral tubes and eight types of the concentric annuli in various range of Reynolds number. The pressure drops in the core tubes and the annuli were much higher than those in the tubes with smooth surface. Therefore, modified correlations to present the experimental results in each flow passage were suggested.

• 대한설비공학회지:설비저널
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• 제16권5호
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• pp.516-524
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• 1987

This paper presents experimental data of fluctuation characteristics of local void fraction of air-water two-phase flow which are associated with the flow pattern, annular gap size and radial location in vertical concentric annuli with coefficient of skewness and kurtosis. The annular gap widths are 13mm, 11mm, and 9mm for a 38m inner diameter as the lucite outer tube. A electrical conductivity probe was used to measure the local void fraction and traversed diametrically from inner wall to outer wall using radial increments of 2mm. It was shown that distribution of the coefficient of skewness and kurtosis, which is related that the one is the asymmetry and the other peakness of local void fraction distribution was influenced by flow pattern, annular gap size and radial location.

• 대한수학회지
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• 제42권5호
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• pp.1057-1069
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• 2005

In this article, we prove the existence of two embedded minimal annuli in a slab which are all bounded by a Jordan convex curve and a straight line.