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Buoyancy eects on heat transfer and temperature proles in horizontal pipe ow of drag-reducing uids

Summary: Buoyancy eects on heat transfer and temperature pro®les
in horizontal pipe Żow of drag-reducing Żuids
K. Gasljevic, G. Aguilar, E.F. Matthys
Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, CA 93106, USA
Received 12 November 1999; received in revised form 7 February 2000
We have studied the extent to which buoyancy eects in horizontal pipe Żows of drag-reducing viscoelastic Żuids
cause distortions to both laminar and turbulent temperature pro®les. In the case of laminar Żows, these distortions
may lead to variations in Nusselt numbers that are larger than those seen for Newtonian pipe Żows under similar
conditions. In the case of turbulent drag-reducing Żows, the eects of buoyancy can also be large and may in turn
result in large errors in estimated Nusselt numbers if not properly accounted for. These errors are quanti®ed and
recommendations are made on how to reduce them. 7 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction
In heated Żows in horizontal pipes, gravity-induced
body forces may result from density variations within
the Żuid. Mori et al. [1,2] have shown Żow visualiza-
tion results for mixed convection in laminar Żows of
Newtonian Żuids in horizontal pipes, demonstrating
that the local variations in the Żuid density lead to
counteracting transverse vortices (or secondary Żow


Source: Aguilar, Guillermo - Department of Mechanical Engineering, University of California at Riverside


Collections: Engineering