Flow Patterns and Heat Transfer Around Six in-Line Circular Cylinders at Low Reynolds Number

Fornarelli, Francesco; Oresta, Paolo; Lippolis, Antonio

doi:10.17654/jphmtfeb2015_001_028

Cited by 16 publications

(11 citation statements)

References 29 publications

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“…However, in case of forced convection the tighter spacing, s/d = 3.6, leads to a higher heat exchange. According to Fornarelli et al [6], such behaviour is related to an enhanced cold fluid entrainment in the gap between two successive cylinders for the s/d = 3.6 case, due to the near field flow oscillation (see fig. 5).…”

Section: Heat Exchange Performancementioning

confidence: 84%

“…The refinement strategies include the limiting of the velocity and temperature difference between two adjacent grid cells every timestep. A detailed and comprehensive grid independence study and a sensitivity analysis on the domain dimension has been carried out as reported in a previous work of the authors [6]. At the inflow uniform flow is imposed with u = 1, v = 0 and T = 0, while at the outflow the spatial variation of the velocity components and temperature in the streamwise direction are imposed as follows: ∂u/∂x = 0, ∂v/∂x = 0 and The numerical results of the force coefficients and heat transfer coefficient are reported.…”

Section: Numerical Setupmentioning

confidence: 99%

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Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

Fornarelli

Lippolis

Oresta

2016

Journal of Heat Transfer

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In this paper we found, by means of numerical simulations, a transition in the oscillatory character of the flow field for a particular combination of buoyancy and spacing in an array of six circular cylinders at a Reynolds number of 100 and Prandtl number of 0.7. The cylinders are iso-thermal and they are aligned with the Earth acceleration (g). According to the array orientation, an aiding or an opposing buoyancy is considered. The effect of natural convection with respect to the forced convection is modulated with the Richardson number, Ri, ranging between −1 and 1. Two values of center to center spacing (s = 3.6d − 4d) are considered. The effects of buoyancy and spacing on the flow pattern in the near and far field are described. Several transitions in the flow patterns are found and a parametric analysis of the dependence of the force coefficients and Nusselt number with respect to the Richardson number is reported. For Ri = −1, the change of spacing ratio from 3.6 to 4 induces a transition in the standard deviation of the force coefficients and heat flux. In fact the transition occurs due to rearrangement of the near field flow in a more ordered wake pattern. Therefore, attention is focused on the influence of geometrical and buoyancy parameters on the heat and momentum exchange and their fluctuations. The available heat exchange models * for cylinders array provide a not accurate prediction of the Nusselt number in the cases here studied.

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Section: Heat Exchange Performancementioning

confidence: 84%

Section: Numerical Setupmentioning

confidence: 99%

Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

Fornarelli

Lippolis

Oresta

2016

Journal of Heat Transfer

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“…Configuration of multiple array of cylinders has been discussed in several works. Effect of gap spacing on vortex shedding of laminar flow past six cylinders arranged in-line are studied by [4] and [5]. They found a flow pattern transition between spacing ratios 3.6 and 4 when drag and lift coefficients change significantly.…”

Section: Introductionmentioning

confidence: 99%

PIV measurements of airflow past multiple cylinders

Wodziak

Sobczyk

2018

EPJ Web Conf.

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Flow characteristics in vicinity of six circular cylinders aligned inline was investigated experimentally by means of PIV method. Experiments were conducted in a low speed closed circuit wind tunnel. Inflow velocity was 1.2 m/s which corresponds to Re=1600 based on the cylinder diameter. Spacing ratio between cylinders L/D was 1.5. Instantaneous and averaged velocity fields were presented. Experiments were designed in order to use their results as a test case for future numerical calculations.

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“…However, the concern about pollutant emissions from coal promotes an efficiency improvement of the entire energy production technology. The optimization of the heat transfer in non-reacting parts [4][5][6] and the integration of renewable energy in conventional energy systems [7] represent just a few examples that indirectly reduce both the coal demand and the CO 2 emissions, for which computational fluid dynamics (CFD) has a key role. However, further developments are required to design low emission pulverized coal burners, characterized by low or negligible NO x emissions and ashes with a very low carbon content.…”

Section: Introductionmentioning

confidence: 99%

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

et al. 2017

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Abstract:In the next few years, even though there will be a continuous growth of renewables and a loss of the share of fossil fuel, energy production will still be strongly dependent on fossil fuels. It is expected that coal will continue to play an important role as a primary energy source in the next few decades due to its lower cost and higher availability with respect to other fossil fuels. However, in order to improve the sustainability of energy production from fossil fuels, in terms of pollutant emissions and energy efficiency, the development of advanced investigation tools is crucial. In particular, computational fluid dynamics (CFD) simulations are needed in order to support the design process of low emission burners. Even if in the literature several combustion models can be found, the assessment of their performance against detailed experimental measurements on full-scale pulverized coal burners is lacking. In this paper, the numerical simulation of a full-scale low-NO x , aerodynamically-staged, pulverized coal burner for electric utilities tested in the 48 MW th plant at the Combustion Environment Research Centre (CCA -Centro Combustione e Ambiente) of Ansaldo Caldaie S.p.A. in Gioia del Colle (Italy) is presented. In particular, this paper is focused on both devolatilization and char burnout models. The parameters of each model have been set according to the coal characteristics without any tuning based on the experimental data. Thanks to a detailed description of the complex geometry of the actual industrial burner and, in particular, of the pulverized coal inlet distribution (considering the entire primary air duct, in order to avoid any unrealistic assumption), a correct selection of both devolatilization and char burnout models and a selection of suited parameters for the NO x modeling, accurate results have been obtained in terms of NO x formation. Since the model parameters have been evaluated a priori, the numerical approach proposed here could be suitable to be applied as a performance prediction tool in the design of pulverized coal burners.

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Flow Patterns and Heat Transfer Around Six in-Line Circular Cylinders at Low Reynolds Number

Abstract: The flow field and the heat transfer around six in-line iso-thermal circular cylinders has been studied by mean of numerical simulations. Two values of the center to center

Cited by 16 publications

References 29 publications

Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

PIV measurements of airflow past multiple cylinders

Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner

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