Large Eddy Simulation of multiple impinging jets in hexagonal configuration – Flow dynamics and heat transfer characteristics

Draksler, Martin; Končar, Boštjan; Cizelj, Leon; Ničeno, Bojan

doi:10.1016/j.ijheatmasstransfer.2017.01.080

Cited by 26 publications

(29 citation statements)

References 31 publications

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“…However, the mechanisms responsible for these streak-like structures near the radial location of the secondary peak remained unclear. Other important aspects like the influence of subgrid-scale modeling in LES of impinging jets [48,49], flow dynamics and heat transfer characteristics in multiple impinging jets [50,51], the effect of wall curvature [52,53], impingement jet in cross-flow [54,55] or jet impingement onto a rotating disc [56] have been also investigated by means of LES and DNS. With regard to numerical studies of oblique impinging jets, it is worth mentioning that only a few LES studies [57,58] and no DNS, except the previous DNS study of isothermal flow by Ries et al [59], have been reported in the literature, even though this specific configuration features very interesting flow properties and is of practical relevance in cooling arrangements for gas turbine blades, allowing one to reduce the size of such systems [9], as well as in numerous other applications.…”

Section: Introductionmentioning

confidence: 99%

Near-Wall Thermal Processes in an Inclined Impinging Jet: Analysis of Heat Transport and Entropy Generation Mechanisms

Ries

Klingenberg

et al. 2018

Energies

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In this work, near-wall thermal transport processes and entropy generation mechanisms in a turbulent jet impinging on a 45 ∘ -inclined heated surface are investigated using a direct numerical simulation (DNS). The objectives are to analyze the subtle mechanisms of heat transport in the vicinity of an inclined impinged wall, to determine the causes of irreversibilities that are responsible for the reduction of performance of impingement cooling applications and to provide a comprehensive dataset for model development and validation. Results for near-wall thermal characteristics including heat fluxes are analyzed. An entropy production map is provided from the second law analysis. The following main outcomes can be drawn from this study: (1) the location of peak heat transfer occurs not directly at the stagnation point; instead, it is slightly shifted towards the compression side of the jet, while at this region, the heat is transported counter to the temperature gradient; (2) turbulent thermal and fluid flow transport processes around the stagnation point are considerably different from those found in other near-wall-dominated flows and are strongly non-equilibrium in nature; (3) heat fluxes appear highly anisotropic especially in the vicinity of the impinged wall; (4) in particular, the heated wall acts as a strong source of irreversibility for both entropy production related to viscous dissipation and to heat conduction. All these findings imply that a careful design of the impinged plate is particularly important in order to use energy in such a thermal arrangement effectively. Finally, this study confirms that the estimation of the turbulent part of the entropy production based on turbulence dissipation rates in non-reacting, non-isothermal fluid flows represents a reliable approximate approach within the second law analysis, likewise in the context of computationally less expensive simulation techniques like RANS and/or LES.

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Section: Introductionmentioning

confidence: 99%

Near-Wall Thermal Processes in an Inclined Impinging Jet: Analysis of Heat Transport and Entropy Generation Mechanisms

Ries

Klingenberg

et al. 2018

Energies

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“…The convective terms of the Navier-Stokes equations are discretized with central-difference scheme, the diffusion terms are discretized by the second order upwind scheme, and the time discretization is bounded second order implicit. The Courant number was equal to 0.5 inside the flow domain [24,25]. The LES simulation was run for eight flow through times, in order to reach statistical convergence.…”

Section: Governing Equationsmentioning

confidence: 99%

Large eddy simulation of turbulent flow and heat transfer in outward transverse and helically corrugated tubes

Wang

Zhang

Liu

et al. 2019

Numerical Heat Transfer, Part A: Applications

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“…A ground fast cooling simulation device was employed to investigate the impact of arrangement and nozzle geometry on the impinging jet's heat transfer [12]. Large eddy simulation was carried out to study the flow dynamics and heat transfer characteristic of multiple impinging jets at high Reynolds numbers, and in a hexagonal configuration [13]. A numerical investigation and design optimization were carried out for impingement cooling system with an array of air jets [14].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Simulation of the Heat Transfer Enhancement on the Twin Impingement Jet Mechanism

et al. 2018

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This article presents a study which sought to enhance heat transfer by employing a twin jet impingement mechanism (TJIM) and investigating the impact of the distance between the nozzles and plate on the Nusselt number (Nu) and heat transfer coefficient. This investigation was additionally based on the measurements of the heat flux temperature micro foil sensor and IR thermal imaging. A computational study of the cooling heated plate, through simulating the electronic components by the TJIM, was investigated using the RNG k-ε turbulence model. The jet-plate position was changed at the different jet-to-plate distances S = 1, 6, and 11 cm, Reynolds number = 17,000. The main flow structure, the static pressure, local and average Nus and heat transfer coefficient, were also examined. The findings have yielded new information about TJIM, and represent a new contribution about the flow and heat transfer characteristics of TJIM, and means of improving the rate of heat transfer in the passive heat transfer technique. The results of the various positions of the TJIM determined that the first model is, in fact, the best model for the heat transfer coefficient and the highest Nu, when S = 1 cm and H = 1 cm. Furthermore, the irregular distribution of the local Nu and the local heat transfer coefficient (h) on the impinged surface are due to the increase or decrease in the turbulence of flow on the measured surface.

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Large Eddy Simulation of multiple impinging jets in hexagonal configuration – Flow dynamics and heat transfer characteristics

Cited by 26 publications

References 31 publications

Near-Wall Thermal Processes in an Inclined Impinging Jet: Analysis of Heat Transport and Entropy Generation Mechanisms

Near-Wall Thermal Processes in an Inclined Impinging Jet: Analysis of Heat Transport and Entropy Generation Mechanisms

Large eddy simulation of turbulent flow and heat transfer in outward transverse and helically corrugated tubes

Experimental and Numerical Simulation of the Heat Transfer Enhancement on the Twin Impingement Jet Mechanism

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