Conjugate heat transfer in the unbounded flow of a viscoelastic fluid past a sphere

• Type: Article in International Scientific Journal
• Date: 2021

Authors

Pimenta, F (Author) Other; Alves, MA (Author) FEUP

Journal

Title: International Journal of Heat and Fluid Flow

Vol. 89

ISSN: 0142-727X

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 0 Citations

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Other information

Authenticus ID: P-00T-SK6

DOI: 10.1016/j.ijheatfluidflow.2021.108784

Abstract (EN): This work addresses the conjugate heat transfer of a simplified PTT fluid flowing past an unbounded sphere in the Stokes regime (Re = 0.01). The problem is numerically solved with the finite-volume method assuming axisymmetry, absence of natural convection and constant physical properties. The sphere generates heat at a constant and uniform rate, and the analysis is conducted for a range of Deborah (0 < De < 100), Prandtl (100 < Pr < 105) and Brinkman (0 < Br < 100) numbers, in the presence or absence of thermal contact resistance at the solid-fluid interface and for different conductivity ratios (0.1 < kappa < 10). The drag coefficient shows a monotonic decrease with De, whereas the normalized stresses on the sphere surface and in the wake first increase and then decrease with De. A negative wake was observed for the two solvent viscosity ratios tested (beta = 0.1 and 0.5), being more intense for the more elastic fluid. In the absence of viscous dissipation, the average Nusselt number starts to decrease with De after an initial increase. Heat transfer enhancement relative to an equivalent Newtonian fluid was observed for the whole range of conditions tested. The dimensionless temperature of the sphere decreases and becomes more homogeneous when its thermal conductivity increases in relation to the conductivity of the fluid, although small changes are observed in the Nusselt number. The thermal contact resistance at the interface increases the average temperature of the sphere, without affecting significantly the shape of the temperature profiles inside the sphere. When viscous dissipation is considered, significant changes are observed in the heat transfer process as Br increases. Overall, a simplified PTT fluid can moderately enhance heat transfer compared to a Newtonian fluid, but increasing De does not necessarily improve heat exchange.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 17