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Influence of Local Flow Acceleration on the Heat Transfer of Submerged and Free-surface Jet Impingement

DOI: 10.1615/IHTC15.fcv.008378
pages 3179-3192

Wilko Rohlfs
Institute of Heat and Mass Transfer, RWTH Aachen University, 52062 Aachen, Germany

Claas Ehrenpreis
Institute of Heat and Mass Transfer, RWTH Aachen University, Aachen, 52056, Germany

Herman D. Haustein
School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel; Institute of Heat and Mass Transfer, RWTH Aachen University, 52062 Aachen, Germany

Oliver Garbrecht
WSA RWTH Aachen

Reinhold Kneer
Institute of Heat and Mass Transfer, RWTH Aachen University, Augustinerbach 6, 52056 Aachen, Germany


KEY WORDS: Convection, Two-phase/Multiphase flow, Impinging jets

Abstract

The present study of low Reynolds number submerged and free-surface jet impingement examines the cause of peaks in the radial distribution of the Nusselt number by way of fully resolved numerical simulation. In a first step, the flow behavior of free-surface and submerged free jets is examined, revealing a different development of the initial velocity profile while traveling towards the impingement wall. The shape of the Nusselt distribution is found to be significantly influenced by the velocity profile close to the wall, however, showing similar trends for both, submerged and free-surface jets. Thus, a local peak in the heat transfer distribution is found to exist not only for submerged but also for free-surface jets under specific conditions (long nozzle-toplate distances and low Reynolds numbers). The causing effect of the local peak is revealed in detail, showing that local flow acceleration in radial direction is the dominant cause for the increasing heat transfer coefficient in flow direction.

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