Heat transfer downstream of a 3D confined square cylinder under flow pulsation

Martín, Elena; Velázquez, A.; Valeije, A.

doi:10.1080/10407782.2018.1562744

Cited by 6 publications

(4 citation statements)

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“…These numerical implementations for pulsating flows (Setup A) and prescribed prism motion (Setup B) were validated previously by the authors comparing with different studies for similar configurations. Validation of the flow pulsation implementation was done in Martin et al (2018) with the experimental work of Ji et al (2008) (both for the isothermal and thermal regimes). Ji’s experiment consisted of a heated square prism placed inside a channel subjected to a pulsating airflow of constant amplitude.…”

Section: Description Of the Numerical Methodsmentioning

confidence: 99%

“…Also, it is to be remarked that studies that use this type of concept configuration (fluid motion at moderate Reynolds in a square section channel with square section prism placed inside) are not uncommon in the specialized literature. For example, regarding pulsating flows, the following references, among others, could be referred to Ji et al (2008), Mulcahey et al (2013), Yu et al (2014), Krishnan et al (2016) and Martin et al (2018). Regarding prism motion, some relevant references are: Celik and Beskok (2009), Singh et al (2009), Reyes et al (2015), Kumar Chauhan et al (2016), Sastre and Velazquez (2017), Ortega-Casanova and Lai (2018), Clemente et al (2019) and Valeije et al (2020).…”

Section: Problem Descriptionmentioning

confidence: 99%

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Comparison of three-dimensional flow mixing via pulsation and dynamical stirring: application to the mixing of parallel streams at different temperatures

Sastre

Martín

Velázquez

et al. 2021

HFF

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Purpose This paper aims to compare the performance of flow pulsation versus flow stirring in the context of mixing of a passive scalar at moderate Reynolds numbers in confined flows. This comparison has been undertaken in two limits: diffusion can be neglected as compared to convection (very large Peclet) and diffusion and convection effects are comparable. The comparison was performed both in terms of global parameters: pumping power and mixing efficiency and local flow topology. Design/methodology/approach The study has been addressed by setting up a common conceptual three-dimensional problem that consisted of the mixing of two parallel streams in a square section channel past a square section prism. Stirring and pulsation frequencies and amplitudes were changed and combined at an inlet Reynolds number of 200. The numerical model was solved using a finite volume formulation by adapting a series of open-source OpenFOAM computational fluid dynamic (CFD) libraries. For cases with flow pulsation, the icoFoam solver for laminar incompressible transient flows was used. For cases with stirring, the icoDyMFoam solver, which uses the arbitrary Lagrangian–Eulerian method for the description of the moving dynamical mesh, was used to model the prism motion. At the local flow topology level, a new method was proposed to analyze mixing. Time evolution of folding and wrinkling of sheets made up of virtual particles that travel along streak lines was quantified by generating lower rank projections of the sheets onto the spaces spanned by the main eigenvectors of an appropriate space-temporal data decomposition. Findings In the limit when convection is dominant, the results showed the superior performance of stirring versus flow pulsation both in terms of mixing and required pumping power. In the cases with finite Peclet, the mixing parameters by stirring and flow pulsation were comparable, but pulsation required larger pumping power than stirring. For some precise synchronization of stirring and pulsation, the mixing parameter reached its maximum, although at the expense of higher pumping power. At the local flow topology level, the new method proposed to quantify mixing has been found to correlate well with the global mixing parameter. Originality/value A new systematic comparative study of two methods, stirring and pulsation, to achieve mixing of passive scalars in the mini scale for confined flows has been presented. The main value, apart from the conclusions, is that both methods have been tested against the same flow configuration, which allows for a self-consistent comparison. Of particular interest is the fact that it has been found that accurate synchronization of both methods yields mixing parameters higher than those associated to both methods taken separately. This suggests that it is possible to synchronize mixing methods of a different nature to achieve optimum designs. The new theoretical method that has been proposed to understand the mixing performance at the local level has shown promising results, and it is the intention of the authors to test its validity in a broader range of flow parameters. All these findings could be taken as potential guidelines for the design of mixing processes in the mini scale in the process industry.

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Section: Description Of the Numerical Methodsmentioning

confidence: 99%

Section: Problem Descriptionmentioning

confidence: 99%

Comparison of three-dimensional flow mixing via pulsation and dynamical stirring: application to the mixing of parallel streams at different temperatures

Sastre

Martín

Velázquez

et al. 2021

HFF

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“…For the simulated cases, Pr was equal to 4.8. µ and k stand for the temperature dependent dimensionless viscosity and thermal conductivity of the fluid. Since the problem has been defined to be studied with water as the working fluid, the empirical correlations for these values have been taken from the works of Martin and Velazquez [22] and Martin et al [23] and made dimensionless accordingly.…”

Section: Mathematical Modelmentioning

confidence: 99%

Impact of Channels Aspect Ratio on the Heat Transfer in Finned Heat Sinks with Tip Clearance

et al. 2022

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A 3D numerical study is used to analyze the flow topology and performance, in terms of heat transfer efficiency and required pumping power, of heat sink devices with different channel aspect-ratio in the presence of tip-clearance. Seven different channel aspect ratios AR, from 0.25 to 1.75, were analyzed. The flow Reynolds numbers Re, based on the average velocity evaluated in the device channels region, were in the range of 200 to 1000. Two different behaviors of the global Nusselt were obtained depending on the flow Reynolds number: for Re<600, the heat transfer increased with the channels aspect ratio, e.g., for Re=400, the global Nusselt number increased by 14% for configuration AR=1.75 when compared to configuration AR=0.25. For Re>600, the maximum Nusselt is obtained for the squared-channel configuration, and, for some configurations, flow destabilization to a unsteady regime appeared. For Re=700, Nusselt number reduced when compared with the squared-channel device, 11% and 2% for configurations with AR=0.25 and 1.75, respectively. Dimensionless pressure drop decreased with the aspect ratio for all cases. In the context of micro-devices, where the Reynolds number is small, these results indicate that the use of channels with high aspect-ratios is more beneficial, both in terms of thermal and dynamic efficiency.

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“…В работах [6,7], также обнаружено увеличение теплоотдачи одиночного цилиндра при вынужденных пульсациях потока. Интенсификация теплообмена наблюдается при принудительных пульсациях потока в трубе [8], при обтекании полуцилиндра [9,10], и других препятствий [11,12]. Не смотря на имеющиеся положительные результаты в применении пульсирующих потоков для интенсификации теплообмена в пучках труб для потоков воздуха [13], воды [14] и масла [15], экспериментальных и теоретических исследований их влияния на очистку внешней поверхности труб в пучке в настоящее время недостаточно [16][17][18].…”

Section: Introductionunclassified

Improving heat exchanger efficiency using the pulsed method of cleaning

Haibullina

Zinnatullin

Ilyin

2020

«Izvestiya vysshikh uchebnykh zavedenii. PROBLEMY ENERGETIKI»

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The fouling of heat exchange equipment leads to serious economic losses in many industries, therefore to find a method to reduce deposits on heat transfer surfaces remains an actual task. In this paper, a practical solution is proposed for the implementation of a pulsating cleaning method of oil coolers as an example. The influence of pulsations on cleaning of the external surface of the heat exchanger is studied by computer modeling with Ansys Fluent. The fluid flow was described by the Navier-Stokes equation, particle motion and their interaction was described by the discrete element method (DEM). In the study, a staggered tube bundle was considered. The pulse frequency 0,3125 Hz, the amplitude referred to the diameter of tube is 35, the Reynolds number 100, the duty cycle of the pulsations 0,25. Oil was chosen as the medium. Evaluation of the pulsating cleaning method was carried out on the basis of the analysis of the mechanics of particle collisions on the surface of the central cylinder in the beam, with stationary and pulsating flow. It was found that the pulsating flow helps to reduce deposits in the front of the cylinder and is not effective in the back. An analysis of the mechanics of particle impact on the heat exchange surface showed that this pulsation mode is more effective for removing plastic deposits.

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Heat transfer downstream of a 3D confined square cylinder under flow pulsation

Cited by 6 publications

References 50 publications

Comparison of three-dimensional flow mixing via pulsation and dynamical stirring: application to the mixing of parallel streams at different temperatures

Comparison of three-dimensional flow mixing via pulsation and dynamical stirring: application to the mixing of parallel streams at different temperatures

Impact of Channels Aspect Ratio on the Heat Transfer in Finned Heat Sinks with Tip Clearance

Improving heat exchanger efficiency using the pulsed method of cleaning

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