TY - JOUR

T1 - Influence of molecular mass of PEG on rheological behaviour of MWCNT-based nanofluids for thermal energy storage

AU - Marcos, Marco A.

AU - Lugo, Luis

AU - Ageev, Sergei V.

AU - Podolsky, Nikita E.

AU - Cabaleiro, David

AU - Postnov, Viktor N.

AU - Semenov, Konstantin N.

N1 - Funding Information: The work is supported by the interuniversity exchange program between Saint Petersburg State University (Russia) and University of Vigo (Spain), by Grant of the Council on grants of the President of the Russian Federation for young scientists MD-2175.2018.3 and by Grants of RFBR ( 18-33-20238 , 18-08-00143 , 19-015-00469 ). The work was also partially supported by “ Ministerio de Economía y Competitividad ” (Spain) and FEDER program through ENE2017-86425-C2-1-R project. Part of this research was performed using the equipment of the Resource Centre “GeoModel” and Centre for Chemical Analysis and Materials Research of Research Park of Saint Petersburg State University. D.C. is recipient of a postdoctoral fellowship from Xunta de Galicia (Spain). Publisher Copyright: © 2020 Elsevier B.V. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/11/15

Y1 - 2020/11/15

N2 - This paper presents original experimental data regarding the rheological characterisation of nanofluids based on poly(ethylene glycol) s with molecular mass of either 200 or 300 g·mol−1 (i.e. PEG-200 or PEG-300) and containing 0.025–0.70 wt% of multi-walled carbon nanotubes (MWCNT). The shear rate dependence of dynamic viscosity (η) was first studied in the temperature range from 278.15 to 313.15 K. Such non-linear viscoelastic experiments revealed that, unlike the neat poly(ethylene glycol)s used as based fluids, MWCNT/PEG-200 and MWCNT/PEG-300 nanofluids exhibited a non-Newtonian pseudoplastic behaviour in the low shear rate region (even in the case of the dispersions prepared at lowest nanoparticle concentrations). Dynamic viscosities measured at ~800 s−1 were compared with the values provided by means of different theoretical or semi-empirical approaches and a good description of our experimental results was obtained (with absolute average deviations ~0.2–0.3%) by using the Maron–Pierce equation modified to take into account the presence of aggregates/agglomerates. Additionally, rheological oscillatory analyses of these nanofluids were also conducted at 288.15 K to identify the linear-viscoelastic region and deep in the analysis of the viscoelastic behaviour of designed dispersions.

AB - This paper presents original experimental data regarding the rheological characterisation of nanofluids based on poly(ethylene glycol) s with molecular mass of either 200 or 300 g·mol−1 (i.e. PEG-200 or PEG-300) and containing 0.025–0.70 wt% of multi-walled carbon nanotubes (MWCNT). The shear rate dependence of dynamic viscosity (η) was first studied in the temperature range from 278.15 to 313.15 K. Such non-linear viscoelastic experiments revealed that, unlike the neat poly(ethylene glycol)s used as based fluids, MWCNT/PEG-200 and MWCNT/PEG-300 nanofluids exhibited a non-Newtonian pseudoplastic behaviour in the low shear rate region (even in the case of the dispersions prepared at lowest nanoparticle concentrations). Dynamic viscosities measured at ~800 s−1 were compared with the values provided by means of different theoretical or semi-empirical approaches and a good description of our experimental results was obtained (with absolute average deviations ~0.2–0.3%) by using the Maron–Pierce equation modified to take into account the presence of aggregates/agglomerates. Additionally, rheological oscillatory analyses of these nanofluids were also conducted at 288.15 K to identify the linear-viscoelastic region and deep in the analysis of the viscoelastic behaviour of designed dispersions.

KW - Density

KW - Multi-walled carbon nanotubes (MWCNT)

KW - Nanofluids

KW - Poly(ethylene glycol) (PEG)

KW - Viscoelastic behaviour

KW - Viscosity

KW - REFRACTIVE-INDEXES

KW - SUSPENSIONS

KW - STABILITY

KW - ELECTRICAL-CONDUCTIVITY

KW - VISCOSITY

KW - VISCOELASTICITY

KW - VOLUMETRIC PROPERTIES

KW - PHASE-CHANGE MATERIALS

KW - POLY(ETHYLENE GLYCOL)

KW - DOPED CARBON NANOTUBES

UR - http://www.scopus.com/inward/record.url?scp=85089883003&partnerID=8YFLogxK

U2 - 10.1016/j.molliq.2020.113965

DO - 10.1016/j.molliq.2020.113965

M3 - Article

AN - SCOPUS:85089883003

VL - 318

JO - Journal of Molecular Liquids

JF - Journal of Molecular Liquids

SN - 0167-7322

M1 - 113965

ER -