Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
Stabilized fem approximations for temperature-dependent viscoplastic fluids
Submission Author:
Flavia Zinani , RS , Brazil
Presenter: Flavia Zinani
doi://10.26678/ABCM.ENCIT2016.CIT2016-0336
Abstract
Viscoplastic fluids are common in many industrial applications such as polymer extrusion and oil well drilling. Viscoplastic functions commonly employed to model such non-Newtonian behavior in numerical simulations usually neglect the thermodependency of rheological properties. In the present study, the aim was to investigate the flow and heat transfer of a thermodependent Herschel-Bulkley fluid employing a Galerkin Least Squares (GLS) Finite Element Method (FEM). In order perform a sensivity analises of thermodependency parameters, the cross-flow and heat transfer over a confined circular cylinder was investigated. The Herschel-Bulkley model was regularized using Papanastasiou’s method, and rheological properties (yield stress and consistency index) were assumed to depend on temperature exponentially, as suggested by the literature. The model was implemented in the context of a self-developed FEM code. The GLS stabilization method was employed in order to guarantee the compatibilization of finite element subspaces and to allow the use of equal-order pressure-velocity elements. A factorial design was employed to evaluate the effects of rheological and thermodependency parameters on heat transfer, fluid dynamics and pressure drop. The ranges of parameter employed were Reynolds number from 1 to 20, Prandtl number from 1 to 10, flow index from 0.4 to 1, Herschel-Bulkley number from 0.1 to 10 and thermodependency parameters for yield stress and consistency index from 0 to 3. It was found that the parameters that most affect heat transfer and fluid dynamics are the Herschel-Bulkley number and flow index. Besides, it was found that when employing thermodependency parameters, heat transfer enhancement is predicted.
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