Please use this identifier to cite or link to this item: https://hdl.handle.net/10216/101412
Author(s): Noele Peres
A. Afonso
M. A. Alves
F. T. Pinho
Title: Heat transfer enhancement in laminar flow of viscoelastic fluids through a rectangular duct
Issue Date: 2009
Abstract: An investigation on convective heat transfer with viscoelastic fluids in arectangular duct is carried out to analyze the influence of secondary flow on heat transferenhancement on account of non-zero second normal-stress differences. The duct has anaspect ratio of 2, constant heat flux at the walls and the three dimensional numericalsimulations use a finite-volume method. The numerical results are compared with theexperimental heat transfer data of Hartnett and Kostic [1] and the influence of naturalconvection on the heat transfer process is also addressed. The viscoelastic fluid is describedby the Phan-Thien-Tanner constitutive equation with non-zero second normal-stressdifference ( N2 ! 0 ). The simulations show an enhancement of heat transfer for viscoelasticfluids, quantified by increased levels of the local and mean Nusselt numbers. The origin ofthis enhancement is the fluid rheology, particularly the shear-thinning nature of theviscoelastic fluid and the existence of the secondary flow induced by the non-zero secondnormal stress differences. In addition, the correct prediction of the experimental results ofHartnett and Kostic [1], requires the inclusion of buoyancy, but this mechanism essentiallydistorts the secondary flow unless there are much larger temperature differences and/ orweaker second normal stress differences than tested. In the present simulations, buoyancy didnot change the global heat transfer, but merely redistributed it, because the buoyancyinducedsecondary flow was weaker than the !2 - induced secondary flow. For thesereasons, the effect of buoyancy decreases with an increase of N2.
Subject: Engenharia mecânica
Mechanical engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia mecânica
Engineering and technology::Mechanical engineering
URI: https://repositorio-aberto.up.pt/handle/10216/101412
Source: CMNE 2009 (Congreso de Métodos Numéricos en Ingenieria)
Document Type: Artigo em Livro de Atas de Conferência Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Livro de Atas de Conferência Internacional

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