Turbulence models impact on the flow and thermal analyses of jet impingement

Kura, Tomasz; Fornalik-Wajs, Elżbieta; Wajs, Jan; Kenjereš, Saša

doi:10.1051/matecconf/201824001016

Cited by 5 publications

(9 citation statements)

References 8 publications

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“…Its physical meaning is related to the fact that, while first peak originates from the jet features itself intensifying the heat transfer, the latter is generated during the formation and evolution of impinging surface boundary layer and also lead to enhanced thermal process. Authors have proven in their research work [15,16] that the chosen turbulence model is suitable to adequately simulate both peaks, thus correctly illustrating the phenomenon. For the results obtained with "case I", the secondary peak occurred slightly earlier and was less sharp.…”

Section: Results Of Main Studies and Discussionmentioning

confidence: 97%

“…At the stagnation point, the values obtained with "case I" assured better accuracy. However, the important feature of local Nusselt number curve, its secondary peak, that occurs for particular combinations of H/D and Reynolds numbers [15,16], was significantly better expressed when the "case II" was used. Its physical meaning is related to the fact that, while first peak originates from the jet features itself intensifying the heat transfer, the latter is generated during the formation and evolution of impinging surface boundary layer and also lead to enhanced thermal process.…”

Section: Results Of Main Studies and Discussionmentioning

confidence: 99%

“…The selected RANS model was the Hanjalic's et al ζ-f model [14]. Authors proved it is suitable for the jet impingement simulations [15,16]. This model consists of four additional equations system, representing k (turbulence kinetic energy), ε (the dissipation of k), ζ (fluctuation of the velocity normal to streamlines v 2 normalized by k), and f (relaxation function), which plays a major role in controlling the turbulence production near the wall:…”

Section: Numerical Modelmentioning

confidence: 99%

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Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses

et al. 2020

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One of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical analysis is still very challenging. The authors’ aim was to construct the numerical model which can represent the real phenomena with good or very good accuracy. Starting with an analysis of single jet and obtaining the agreement with experimental data, it will be possible to extend the model towards the whole minijets heat exchanger. The OpenFOAM software, Bracknell, UK was used for that purpose, with our own implementation of the ζ-f turbulence model. The most difficult area to model is the stagnation region, where the thermal effects are the most intensive and, at the same time, strongly affected by the conditions in the pipe/nozzle/orifice of various size (conventional, mini, micro), from which the jet is injected. In the following article, summary of authors’ findings, regarding significance of the velocity profile and turbulence intensity at the jet place of discharge are presented. In addition, qualitative analysis of the heat transfer enhancement is included, in relation to the inlet conditions. In the stagnation point, Nusselt number differences reached the 10%, while, in general, its discrepancy in relation to inlet conditions was up to 23%.

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Section: Results Of Main Studies and Discussionmentioning

confidence: 97%

Section: Results Of Main Studies and Discussionmentioning

confidence: 99%

Section: Numerical Modelmentioning

confidence: 99%

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Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses

et al. 2020

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“…The stainless steel radial recuperators [16] or the ceramic plate microchannel heat exchangers [14] are also considered. However, the most promising seem to be the heat exchangers with the micro-jets technology -intensive experimental [29] and numerical [11,12] investigations of their development are being conducted at the moment. The direct hybrid system has one degree of freedom less than the indirect system.…”

Section: Direct Hybrid Systemmentioning

confidence: 99%

Design Analysis of Hybrid Gas Turbine‒Fuel Cell Power Plant in Stationary and Marine Applications

Kwaśniewski

Piwowarski

2020

Polish Maritime Research

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The paper concerns the design analysis of a hybrid gas turbine power plant with a fuel cell (stack). The aim of this work was to find the most favourable variant of the medium capacity (approximately 10 MW) hybrid system. In the article, computational analysis of two variants of such a system was carried out. The analysis made it possible to calculate the capacity, efficiency of both variants and other parameters like the flue gas temperature. The paper shows that such hybrid cycles can theoretically achieve extremely high efficiency over 60%. The most favourable one was selected for further detailed thermodynamic and flow calculations. As part of this calculation, a multi-stage axial compressor, axial turbine, fuel cell (stack) and regenerative heat exchanger were designed. Then an analysis of the profitability of the installation was carried out, which showed that the current state of development of this technology and its cost make the project unprofitable. For several years, however, tendencies of decreasing prices of fuel cells have been observed, which allows the conclusion that hybrid systems will start to be created. This may apply to both stationary and marine applications. Hybrid solutions related to electrical power transmission, including fuel cells, are real and very promising for smaller car ferries and shorter ferry routes.

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“…The results exhibited some issues referring to an accuracy and further research was necessary to make a proper choice. It was already performed and published in [39,40]. In both articles, which concerned single jet impingement on both flat and non-flat surfaces, the superior performance of the Hanjalic's ζ-f model over others investigated was proven.…”

Section: Introduction 1flat Surface Jet Impingementmentioning

confidence: 99%

Curved Surface Minijet Impingement Phenomena Analysed with ζ-f Turbulence Model

et al. 2021

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The jet impingement phenomenon plays an important role among the heat transfer intensification methods. Very often its application and analyses refer to simple flat surfaces, while there is a lack of information in the literature for cases addressing curved surfaces. In the present work, the single jet impingement on the non-flat (concave and convex) surface is studied for a wide range of geometries, which originate from the mini-jet heat-exchanger design. The numerical simulations were performed by an advanced ζ-f turbulence model implemented in the open-source OpenFOAM (ESI-OpenCFD Ltd, Bracknell, United Kingdom) code. Noticeable differences in the phenomena occurring on the convex and concave surfaces were identified in the stagnation zone. Besides, the existence and location of the secondary peak in the Nusselt number distribution differed between the cases. These distributions were influenced by the shape of geometry, which determined flow characteristics and resulting heat transfer performance. The origins of these differences were looked at in the turbulence characteristics close to the impinged surface of the stagnations zone and its vicinity, where turbulence kinetic energy and enstrophy were analysed. It was stated that the differences are already noticeable for the single jet impingement case, but they might sum up when multiple jets are considered. Therefore, here presented results would be important for the analysis of the overall unit of mentioned mini-jets heat-exchanger.

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Turbulence models impact on the flow and thermal analyses of jet impingement

Cited by 5 publications

References 8 publications

Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses

Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses

Design Analysis of Hybrid Gas Turbine‒Fuel Cell Power Plant in Stationary and Marine Applications

Curved Surface Minijet Impingement Phenomena Analysed with ζ-f Turbulence Model

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