Time-dependent structural breakdown of microencapsulated phase change materials suspensions

Cao, Vinh Duy; Bringas, Carlos Salas; Schüller, Reidar Barfod; Szczotok, Anna M.; Kjøniksen, Anna–Lena

doi:10.1080/01932691.2018.1462194

Cited by 7 publications

(13 citation statements)

References 21 publications

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“…When this nonencapsulated PCM is in the liquid phase, it may disrupt the particle−particle interactions that cause local shearthickening in the PCS B sample. The presence of melted paraffin resulting in a disruption of mPCM interactions was also observed by Cao et al 30 Identifying this increase is critical for flow-based systems that operate near the melting point of the PCS.…”

Section: ■ Experimental Methodssupporting

confidence: 55%

“…PCSs and mPCSs are known to be shear-thinning in their flow behavior at high dispersed concentrations; ,− such slurries will have a decreasing pressure drop at higher shear rates . At a low PCM volume fraction, the slurry can display simple Newtonian flow behavior but can adopt non-Newtonian behavior as the dispersed particles increase in volume fraction. ,, Since all thermal storage and extraction applications demand a long life of repeated flow and phase change, hysteresis analysis is also necessary. , Thermal storage applications require a high concentration of PCMs, to maximize the thermal storage potential. In our previous work, we found that PCM concentration also increases the fluid’s viscosity, and a critical concentration exists where the viscosity would result in a significant parasitic energy loss .…”

Section: Introductionmentioning

confidence: 99%

“…17,27,28 Since all thermal storage and extraction applications demand a long life of repeated flow and phase change, hysteresis analysis is also necessary. 29,30 Thermal storage applications require a high concentration of PCMs, to maximize the thermal storage potential. In our previous work, we found that PCM concentration also increases the fluid's viscosity, and a critical concentration exists where the viscosity would result in a significant parasitic energy loss.…”

Section: ■ Introductionmentioning

confidence: 99%

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Rheological Behavior of Phase Change Slurries for Thermal Energy Applications

et al. 2022

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Phase change materials that leverage the latent heat of solid−liquid transition have many applications in thermal energy transport and storage. When employed as particles within a carrier fluid, the resulting phase change slurries (PCSs) could outperform present-day single-phase working fluids�provided that viscous losses can be minimized. This work investigates the rheological behavior of encapsulated and nonencapsulated phase change slurries (PCSs) for applicability in flowing thermal energy systems. The physical and thermal properties of the PCS candidates, along with their rheological behavior, are investigated below and above their phase transition points at shear rates of 1−300 s −1 , temperatures of 20−80 °C, and concentrations of 15−37.5 wt %. The effect of shell robustness and melting on local shear thickening and global shear thinning is discussed, followed by an analysis of the required pumping power. A hysteresis analysis is performed to test the transient response of the PCS under a range of shear rates. We assess the complex viscoelastic behavior by employing oscillatory flow tests and by delineating the flow indices�flow consistency index (K) and flow behavior index (n). We identify a viscosity limit of 0.1 Pa•s for optimal thermal performance in high-flow applications such as renewable geothermal energy.

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Section: ■ Experimental Methodssupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Rheological Behavior of Phase Change Slurries for Thermal Energy Applications

et al. 2022

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“…Several models have been proposed in the literature to describe the time-dependent behavior of complex materials upon constant shearing. In particular, the second-order structural kinetic model (SKM) has been successfully applied to study the time dependence of several food suspensions, emulsions and pastes [ 9 , 13 , 33 , 34 , 35 ]. For example, Nguyen et al used the SKM to study the time-dependent yield stress behavior of waxy maize starch pastes [ 33 ].…”

Section: Resultsmentioning

confidence: 99%

Non-Invasive Rheo-MRI Study of Egg Yolk-Stabilized Emulsions: Yield Stress Decay and Protein Release

et al. 2022

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A comprehensive understanding of the time-dependent flow behavior of concentrated oil-in-water emulsions is of considerable industrial importance. Along with conventional rheology measurements, localized flow and structural information are key to gaining insight into the underlying mechanisms causing time variations upon constant shear. In this work, we study the time-dependent flow behavior of concentrated egg-yolk emulsions with (MEY) or without (EY) enzymatic modification and unravel the effects caused by viscous friction during shear. We observe that prolonged shear leads to irreversible and significant loss of apparent viscosity in both emulsion formulations at a mild shear rate. The latter effect is in fact related to a yield stress decay during constant shearing experiments, as indicated by the local flow curve measurements obtained by rheo-MRI. Concurrently, two-dimensional D-T2 NMR measurements revealed a decrease in the T2 NMR relaxation time of the aqueous phase, indicating the release of surface-active proteins from the droplet interface towards the continuous water phase. The combination of an increase in droplet diameter and the concomitant loss of proteins aggregates from the droplet interface leads to a slow decrease in yield stress.

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“…On the other hand, PCM suspended in HTF, which is called PCM slurry (PCM-S), was reported to store or carry a greater amount of thermal energy compared to PCM particles that are not in direct contact with HTF (Salunkhe and Shembekar 2012 ). Although PCM suspended in HTF increases the viscosity of the fluid, hence the required pumping power, such an effect remains within acceptable limits (Alva et al 2017 ; Al-Waeli et al 2019b ; Cao et al 2019 ; Trivedi and Parameshwaran 2020 ). Nonetheless, PCM-Ss have a few issues that must be addressed.…”

Section: Introductionmentioning

confidence: 99%

Encapsulated Phase Change Material Slurries as Working Fluid in Novel Photovoltaic Thermal Liquid Systems: A Comprehensive Review

Yeşilyurt

Çomaklı

2023

Iran J Sci Technol Trans Mech Eng

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Today, energy generation from renewable energy sources is of great interest. Photovoltaic (PV) systems, in this regard, have much to offer, but they suffer from low efficiency, which further deteriorates due to overheating under insolation. So, they need removal of heat from their bodies for better efficiency, which resulted in the introduction of PV-Thermal (PVT) systems, which feature heat transfer fluids (HTF) to draw the heat and deliver it to other systems that make use of it. Nevertheless, the best HTF has yet to be developed. Water-based fluids with additives or nanoparticles seemed like a good choice until HTFs that featured the use of encapsulated phase change materials (ePCM) were proposed. The findings of early studies and subsequent research revealed that the use of ePCM slurries (ePCM-Ss) as the working fluid in PVT systems increased the thermal efficiency, electrical efficiency, and overall efficiency without a notable increase in pumping power. However, preparation of ePCM-Ss is much more complex in many aspects compared to conventional HTFs, as it involves numerous parameters, including but not limited to the use of various shell and core materials, the variety of production methods, the homogeneity of the resulting capsules, the use of additives, the core to shell ratio, and the mass fraction of ePCM in the slurry. All these require an extensive and exhaustive study with quite a lot of background knowledge and interdisciplinary collaboration, as the proper selection of PCM materials and synthesis methods, as well as the correct concentration in the best CF, involve several aspects and expertise in a number of other fields. These parameters also significantly diversify and differentiate ePCM-S by affecting its suspension stability, rheological properties, and thermal properties. In recent years, PCMs have become an attractive research field for researchers due to their advantages. Although there are quite a number of studies addressing ePCM-S, none provide a holistic approach, and they just deal with a certain aspect of this broad topic. This study, therefore, aims to constitute a fundamental guide to refer to from the very beginning to the final implementation of the ePCM-Ss as the working fluid in PVT systems by addressing all steps, aspects, and almost all effective parameters in terms of advantages, disadvantages, challenges, and opportunities.

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Time-dependent structural breakdown of microencapsulated phase change materials suspensions

Cited by 7 publications

References 21 publications

Rheological Behavior of Phase Change Slurries for Thermal Energy Applications

Rheological Behavior of Phase Change Slurries for Thermal Energy Applications

Non-Invasive Rheo-MRI Study of Egg Yolk-Stabilized Emulsions: Yield Stress Decay and Protein Release

Encapsulated Phase Change Material Slurries as Working Fluid in Novel Photovoltaic Thermal Liquid Systems: A Comprehensive Review

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