Experimental investigation of the impact of elastic turbulence on heat transfer in a serpentine channel

Abed, Waleed M.; Whalley, Richard D.; Dennis, David; Poole, Robert J.

doi:10.1016/j.jnnfm.2016.03.003

Cited by 71 publications

(76 citation statements)

References 35 publications

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“…Presented Associated molecular fluid properties are determined from Abed et al [11] and are given in Table 2. For most conditions of the present study (with the exception of viscosity), property values for 80 ppm, 100 ppm, and 150 ppm polyacrylamide solutions with 65 percent sucrose, are within a few percent of values for the 65 percent sucrose solution by itself.…”

Section: Resultsmentioning

confidence: 99%

“…When each solution is prepared, the appropriate polymer concentration (as quantified using PAAm) is employed, along with 1 percent NaCl, and 65 percent sucrose. The procedure for mixing the stock solution is adopted from Abed et al [11].…”

Section: Polyacrylamide Polymer Solutionsmentioning

confidence: 99%

“…Numerical investigations are described by Zhang et al [9,10] which address connections between elastic turbulence and enhancement of local flow mixing. Abed et al [11], and Whalley et al [12] describe enhancements in flow mixing from elastic turbulence which often result in enhancements of convective heat transfer rates, when compared for the same configuration and same experimental conditions. Of these investigations, Abed et al [11] experimentally consider convective heat transfer and fluid flow within a square cross-section serpentine channel with both polymeric viscoelastic fluids, and with constant-viscosity Newtonian Boger solutions as a basis of comparison.…”

Section: Introductionmentioning

confidence: 99%

“…Uncertainty values of experimentally measured quantities. Thermal properties of working fluids, where viscosity, density, specific heat, and thermal conductivity are from Abed et al[11].…”

mentioning

confidence: 99%

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Elastic turbulence influences and convective heat transfer within a miniature viscous disk pump

Copeland

Ren

et al. 2017

International Journal of Heat and Mass Transfer

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Elastic turbulence is employed within the present investigation to enhance convective heat transfer at very small scales and at very low Reynolds numbers. A miniature viscous disk pump or VDP is utilized to investigate flow and heat transfer, where the latter are based upon energy balance measurements which utilize the mixed-mean temperature at the inlet and outlet of the viscous disk pump passage. The overall heat transfer rate is determined based upon a constant surface temperature thermal boundary condition, and upon a log-meantemperature difference approach. The VDP operates at rotation speeds of 500 RPM, 1000 RPM, 1500 RPM, 1800 RPM, and 2000 RPM, which produce overall shear rates across the flow cross section of 146.05 1/s, 292.1 1/s, 438.15 1/s, 525.78 1/s, and 584.2 1/s. A channel depth of 640 µm is employed. Elastic turbulence is induced by adding polyacrylamide to water solutions with 65 percent sucrose by mass. Significant enhancements of mixing and transport are observed, which are associated with the onset and development of elastic turbulence. Such behavior is verified, relative to an increased viscosity Boger fluid, using flow visualization results, rheometer viscosity variations with shear rate, and increases of overall magnitudes of convective heat transfer coefficient, which are augmented by as high as 240 percent. These comparisons are assessed relative to the Newtonian Boger fluid (which generally does not change viscosity as shear rate varies) at the same rotation speed, shear rate, flow passage height, and inlet temperature. As polymer concentration increases, elastic turbulence effects become more pronounced, and heat transfer coefficient magnitudes increase. This occurs such that Nusselt number ratios are strongly correlated with the meansquare magnitude of scalar temperature fluctuations at the outlet of the VDP. As a result, remarkable heat transfer coefficient enhancements due to elastic turbulence are demonstrated.

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Section: Resultsmentioning

confidence: 99%

Section: Polyacrylamide Polymer Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Uncertainty values of experimentally measured quantities. Thermal properties of working fluids, where viscosity, density, specific heat, and thermal conductivity are from Abed et al[11].…”

mentioning

confidence: 99%

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Elastic turbulence influences and convective heat transfer within a miniature viscous disk pump

Copeland

Ren

et al. 2017

International Journal of Heat and Mass Transfer

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“…In this regime the velocity field, although remaining smooth in space, becomes chaotic and develops a power-law energy spectrum, which enhances the mixing properties of the flow. While the use of elastic turbulence in microfluidics is now well established [6][7][8][9][10], new potential applications have recently emerged, namely in oil extraction from porous rocks [11].…”

mentioning

confidence: 99%

Emergence of chaos in a viscous solution of rods

2017

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It is shown that the addition of small amounts of microscopic rods in a viscous fluid at low Reynolds number causes a significant increase of the flow resistance. Numerical simulations of the dynamics of the solution reveal that this phenomenon is associated to a transition from laminar to chaotic flow. Polymer stresses give rise to flow instabilities which, in turn, perturb the alignment of the rods. This coupled dynamics results in the activation of a wide range of scales, which enhances the mixing efficiency of viscous flows.In a laminar flow the dispersion of substances occurs by molecular diffusion, which operates on extremely long time scales. Various strategies have therefore been developed, particularly in microfluidic applications, to accelerate mixing and dispersion at low fluid inertia [1][2][3]. The available strategies are commonly divided into two classes, passive or active, according to whether the desired effect is obtained through the specific geometry of the flow or through an oscillatory forcing within the fluid [2]. An alternative method for improving the mixing properties of low-Reynolds-number flows was proposed by Groisman and Steinberg [4] and consists in adding elastic polymers to the fluid. If the inertia of the fluid is low but the elasticity of polymers is large enough, elastic stresses give rise to instabilities that ultimately generate a chaotic regime known as "elastic turbulence" [5]. In this regime the velocity field, although remaining smooth in space, becomes chaotic and develops a power-law energy spectrum, which enhances the mixing properties of the flow. While the use of elastic turbulence in microfluidics is now well established [6][7][8][9][10], new potential applications have recently emerged, namely in oil extraction from porous rocks [11].In this Letter we propose a novel mechanism for generating chaotic flows at low Reynolds numbers that does not rely on elasticity. It is based on the addition of rigid rodlike polymers. At high Reynolds numbers, elasticand rigid-polymer solutions exhibit remarkably similar macroscopic behavior (e.g., Refs. [12][13][14][15]). In both cases the turbulent drag is considerably reduced compared to that of the solvent alone. In particular, when either type of polymer is added in sufficiently high concentrations to a turbulent channel flow of a Newtonian fluid, the velocity profile continues to depend logarithmically on the distance from the walls of the channel, but the mean velocity increases to a value known as maximum-drag-reduction asymptote. Here we study whether or not the similarity between elastic-and rigid-polymer solutions carries over to the low-Reynolds-number regime, i.e whether or not the addition of rigid polymers originates a regime similar to elastic turbulence.We consider a dilute solution of inertialess rodlike polymers. The polymer phase is described by the symmetric unit-trace tensor field R(x, t) = n i n j , where n is the orientation of an individual polymer and the average is taken over the polymers contained in a vol...

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Periodic Flows in Microfluidics

Mudugamuwa,

Roshan,

Hettiarachchi

et al. 2024

Small

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Microfluidics, the science and technology of manipulating fluids in microscale channels, offers numerous advantages, such as low energy consumption, compact device size, precise control, fast reaction, and enhanced portability. These benefits have led to applications in biomedical assays, disease diagnostics, drug discovery, neuroscience, and so on. Fluid flow within microfluidic channels is typically in the laminar flow region, which is characterized by low Reynolds numbers but brings the challenge of efficient mixing of fluids. Periodic flows are time‐dependent fluid flows, featuring repetitive patterns that can significantly improve fluid mixing and extend the effective length of microchannels for submicron and nanoparticle manipulation. Besides, periodic flow is crucial in organ‐on‐a‐chip (OoC) for accurately modeling physiological processes, advancing disease understanding, drug development, and personalized medicine. Various techniques for generating periodic flows have been reported, including syringe pumps, peristalsis, and actuation based on electric, magnetic, acoustic, mechanical, pneumatic, and fluidic forces, yet comprehensive reviews on this topic remain limited. This paper aims to provide a comprehensive review of periodic flows in microfluidics, from fundamental mechanisms to generation techniques and applications. The challenges and future perspectives are also discussed to exploit the potential of periodic flows in microfluidics.

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Experimental investigation of the impact of elastic turbulence on heat transfer in a serpentine channel

Cited by 71 publications

References 35 publications

Elastic turbulence influences and convective heat transfer within a miniature viscous disk pump

Elastic turbulence influences and convective heat transfer within a miniature viscous disk pump

Emergence of chaos in a viscous solution of rods

Periodic Flows in Microfluidics

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