Studies of mixed convection in vertical tubes

Jackson, J. D.; Cotton, Mark; Axcell, Brian

doi:10.1016/0142-727x(89)90049-0

Cited by 417 publications

(128 citation statements)

References 41 publications

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“…In the recent assessment of the performance of a variety of turbulence models in simulating the mixed convection in vertical tubes, which particularly compared the results from the RANS-based models and the DNS results [14], the dominant mechanism that caused laminarization and deterioration of heart transfer was consistently found as the indirect influence of the buoyancy force on the turbulence. These previous results [13][14][15][16] confirmed that the RANS approaches are suitable to attack the mixed convection problems. As an illustrative example to justify the selection of the turbulence model for this study, three sets of wall temperature (T w ) distributions on the jet and back walls obtained from (a) RANS k-(b) RANS k-(c) Reynolds Stress Model (RSM) models are compared with (d) experimental measurements generated by this research project, Fig.…”

Section: Numerical Treatmentssupporting

confidence: 64%

“…The convergence criterion was pre-set in the STAR CD code as such that the normalized residuals for the mass and momentum equations were smaller than 10 -4 , and the residual of the energy equation was less than 10 This particular cooling application involves mixed convection with complex buoyancy effects on the heat transfer performance. Several previous studies have been conducted on the implementation of various turbulence models to resolve the mixed convection phenomena [13][14]. The complexities are mostly associated with the near-wall flow interaction between the velocity field and the turbulence production for buoyancy-aided and buoyancy-opposed flows.…”

Section: Numerical Treatmentsmentioning

confidence: 99%

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Numerical Simulation of Turbulent Flow and Heat Transfer in an Anti- Gravity Blind Duct with Tangential Entry Jet

Chang¹

2011

TOTHERJ

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This numerical study investigates the flow and heat transfer characteristics in a vertical square blind duct with the coolant fed by a tangential entry jet. The detailed Nusselt number (Nu) distributions over the five constituent walls of the blind duct are calculated at duct (jet) Reynolds numbers Re(Re j ) of 5000(20000), 7000(28000) and 10000(40000) using the commercial CFD Star CD code. As an attempt to explore the buoyancy effect on heat transfer performances, three different heat fluxes, which vary the gravitational Grashof numbers (Gr g ) at the fixed Re, are imposed on each duct wall to vary the buoyancy levels. The jet-induced flow phenomena in the blind duct exhibit various heat transfer impacts on the five duct walls over which the different near-wall flow structures are generated. This is demonstrated by cross-examining the detailed Nu distributions and the area-averaged Nusselt number ( Nu ) over the five duct walls at the tested Re and Gr g . The cross-plane swirls induced by the tangential entry jet together with the impinging jet flows considerably elevate the Heat Transfer Enhancement (HTE) performances in the blind duct. Within the parametric conditions simulated, the ratios of Nu to the Dittus-Boelter levels (Nu ) over the jet wall, back wall, impingement wall, side wall and end wall are respectively raised to 3-5.7, 2.8-5.6, 3-5.8, 2.7-4.8 and 3.1-6.1; while the HTE ratios ( Nu /Nu ) over these duct walls consistently decrease as Re increases.

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Section: Numerical Treatmentssupporting

confidence: 64%

Section: Numerical Treatmentsmentioning

confidence: 99%

Numerical Simulation of Turbulent Flow and Heat Transfer in an Anti- Gravity Blind Duct with Tangential Entry Jet

Chang¹

2011

TOTHERJ

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“…(By contrast, heat transfer is always enhanced in descending flow.) The monograph of Petukhov and Polyakov [1988] and the review papers of Jackson et al [1989] and Jackson [2006] provide extended discussions of heat transfer performance under mixed convection conditions. A dimensionless group known as the 'buoyancy parameter', Bo, is used to characterize the extent of buoyancy influence.…”

Section: Nomenclaturementioning

confidence: 99%

“…A dimensionless group known as the 'buoyancy parameter', Bo, is used to characterize the extent of buoyancy influence. The buoyancy parameter was developed in the semi-empirical analysis of Hall and Jackson [1969] and is written here in the form quoted by Jackson et al [1989]:…”

Section: Nomenclaturementioning

confidence: 99%

Refined Eddy Viscosity Schemes and Large Eddy Simulations for Ascending Mixed Convection Flows

Keshmiri

Addad

Cotton

et al. 2008

International Symposium on Advances in Computational Heat Transfer

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The present work is concerned with the modelling of ascending turbulent ('mixed convection') flow in a vertical heated pipe. All fluid properties are assumed to be constant and buoyancy is accounted for within the Boussinesq approximation. Four Eddy Viscosity Models (EVMs) are examined against experimental and numerical (direct simulation) data. The EVMs embody distinct physical refinements with respect to the parent high-Reynolds-number k-ε model. New Large Eddy Simulations (LES) are also presented. Three different CFD codes have been employed in the study: 'CONVERT', 'Code_Saturne', and 'STAR-CD', which are respectively inhouse, industrial, and commercial packages. In general, forced convection flows are best resolved by the LES computations and Cotton-Ismael turbulence model (Cotton and Ismael [1998]). In mixed convection flows the picture changes and the Launder-Sharma closure [Launder and Sharma, 1974] and 'Manchester f v 2 − ' model [Keshmiri et al., 2008] are in closest agreement with the direct simulation heat transfer data. Under conditions of maximum heat transfer impairment, the mean flow and turbulence profiles are best captured by the Large Eddy Simulations and LS and f v 2 − models. However, no single scheme could be said to be in excellent agreement with the data examined.

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“…The primary focus of this paper is on ascending mixed convection flows representing coolant flow in the fuel elements of the UK fleet of Advanced Gas-cooled Reactors (AGRs) [2]. The review papers of Jackson et al [3] and Jackson [4] provide extended discussions of heat transfer performance under mixed convection conditions. The most popular computational fluid dynamics (CFD) technique adopted in simulating mixed convection flows is based on the solution of Reynolds-averaged Navier-Stokes (RANS) equations, and among the possible turbulence models available to close these equations, eddy-viscosity models (EVMs) have been employed by the majority of researchers including Abdelmeguid and Spalding [5], Tanaka et al [6], Cotton and Jackson [7], Mikielewicz et al [8], Richards et al [9], Kim et al [10], and Keshmiri et al [11][12][13], among others.…”

Section: Introductionmentioning

confidence: 99%

Assessment of a common nonlinear eddy-viscosity turbulence model in capturing laminarization in mixed convection flows

Keshmiri

Revell

Darabkhani

2015

Numerical Heat Transfer, Part A: Applications

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Laminarization is an important topic in heat transfer and turbulence modeling. Recent studies have demonstrated that several well-known turbulence models failed to provide accurate prediction when applied to mixed convection flows with significant re-laminarization effects. One of those models, a well-validated cubic nonlinear eddy-viscosity model, was observed to miss this feature entirely. This paper studies the reasons behind this failure by providing a detailed comparison with the baseline Launder-Sharma model. The difference is attributed to the method of near-wall damping. A range of tests have been conducted and two noteworthy findings are reported for the case of flow re-laminarization. ARTICLE HISTORY

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Studies of mixed convection in vertical tubes

Cited by 417 publications

References 41 publications

Numerical Simulation of Turbulent Flow and Heat Transfer in an Anti- Gravity Blind Duct with Tangential Entry Jet

Numerical Simulation of Turbulent Flow and Heat Transfer in an Anti- Gravity Blind Duct with Tangential Entry Jet

Refined Eddy Viscosity Schemes and Large Eddy Simulations for Ascending Mixed Convection Flows

Assessment of a common nonlinear eddy-viscosity turbulence model in capturing laminarization in mixed convection flows

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