High Péclet number heat exchange between cocurrent streams |
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Authors: | P Plaschko |
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Institution: | (1) Departamento de Física, Universidad Autónoma Metropolitana, Unidad Iztapalapa, 09430 Mexico City, Mexico e-mail: peter@xanum.uam.inx Fax: 52-5-804-4611, MX |
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Abstract: | Summary This paper concentrates on the analysis of the heat transfer between two cocurrent laminar flows in parallel channels. For
high values of the Péclet number Pe, a boundary layer arises near the wall separating the streams. Matched asymptotic expansions (MAE) are used to obtain approximate
solutions. We consider arbitrary inlet temperatures and derive higher-order corrections of the boundary problem. The separating
wall is supposed to be sufficiently thin to neglect the heat conduction in it. Analyticity and adiabatic conditions at the
outer walls impose restrictions on the inlet temperatures. It turns out, however, that only the inlet temperatures at the
wall separating the two fluids enter the leading-order problem. The Nusselt numbers thus calculated are in the leading order
proportional to (Pe/x)1/3, where x is the stream-wise coordinate. An estimate of the thickness of the separating wall to validate the MAE approach is obtained.
It is also demonstrated that the MAE analysis is unable to describe the heat exchange of counterflowing fluids.
Received 9 June 1999; accepted for publication 17 November 1999 |
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Keywords: | Heat conduction laminar boundary layer asymptotic expansion |
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