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Heat Transfer Research
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ISSN Imprimer: 1064-2285
ISSN En ligne: 2162-6561

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Heat Transfer Research

DOI: 10.1615/HeatTransRes.v41.i5.20
pages 509-520

Numerical Investigations of Opposing Mixed Convection Heat Transfer in Vertical Flat Channel. 1. Laminar Mixed Convection and Transition to Vortex Flow in the Case of Symmetrical Heating

Arunas Sirvydas
Lithuanian Energy Institute, Branduolinës inþinerijos problemø laboratorija, Breslaujos str. 3, LT-44403 Kaunas
Robertas Poskas
Lithuanian Energy institute; Kaunas Univerity of Technology, Kaunas, Lithuania

RÉSUMÉ

In this paper we present the results of numerical investigation into the local opposing mixed convection heat transfer in a vertical flat channel with symmetrical heating in laminar airflow. Numerical two-dimensional simulation was performed using FLUENT 6.1 code. The investigations were performed under steady state flow conditions in airflow of 0.1; 0.2 and 0.4 MPa pressure at the Reynolds numbers from 1.5·103 up to 4.3·103 with the Grq number varying from 1.65·105 to 3.1·109 in order to define the effect of the influence of buoyancy on heat transfer. Numerical modeling demonstrates that under small buoyancy effect there are only small transformations in the velocity profile but flow is oriented downward (direction of forced flow). With increase in buoyancy forces, the flow separation occurs at some distance from the beginning of the heated channel section. With further increase in buoyancy, the position point of flow separation moves towards the beginning of a heated section. The channel wall temperature decreases noticeably at the flow separation point. Correlations for calculating heat transfer in the laminar mixed convection region and for the determination of the position of flow separation from the wall are suggested.

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