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Asymptotes of maximum friction and heat transfer reductions for drag-reducing surfactant solutions

Summary: Asymptotes of maximum friction and heat transfer reductions
for drag-reducing surfactant solutions
Guillermo Aguilar *,1
, Kazimir Gasljevic, Eric F. Matthys
Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
Received 27 June 2000; received in revised form 11 October 2000
A new maximum drag reduction asymptote (MDRA) for surfactant solutions is presented. Various concentrations
including cationic and non-ionic surfactant solutions were used to experimentally determine this asymptote. It is shown
that if solvent viscosity is used to compute Reynolds and Prandtl numbers for viscous solutions, it leads to underes-
timations of the friction coecient. To avoid uncertainties in the selection of the ¯uids viscosity, most solutions used
were intentionally conditioned so their shear viscosity was water-like in the ranges covered. Using the same solutions, a
maximum heat transfer reduction asymptote (MHTRA) was also determined ą a correlation that did not exist for
surfactants until now. Finally, by using slightly modiŽed deŽnitions to quantify the heat transfer and drag reductions
(TRH and TRD), it is possible to express the ratio between the MHTRA and MDRA with a constant value of 1.06,
independent of Reynolds number. This relationship can be used as an auxiliary criterion to determine whether or not a
solution is asymptotic when there is an uncertainty about the shear viscosity. Ķ 2001 Elsevier Science Ltd. All rights
Keywords: Asymptotes; Drag reduction; Heat transfer reduction; Surfactants
1. Introduction


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


Collections: Engineering