Smart control of drag reduction and heat transfer in a channel flow

Since the discovery of the Toms effect (Toms, 1948), polymers as drag-reducing additives have been widely used to reduce the undesired drag that occurs over long-distance transportation of liquids. However, less attention has been focused on this area of research, especially in the case of re circul...

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Main Authors: Zhou, Tongming., Nguyen, Nam Trung., Leong, Kai Choong.
Other Authors: School of Mechanical and Aerospace Engineering
Format: Research Report
Language:English
Published: 2010
Subjects:
Online Access:http://hdl.handle.net/10356/42324
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-423242023-03-04T18:06:48Z Smart control of drag reduction and heat transfer in a channel flow Zhou, Tongming. Nguyen, Nam Trung. Leong, Kai Choong. School of Mechanical and Aerospace Engineering DRNTU::Engineering::Mechanical engineering Since the discovery of the Toms effect (Toms, 1948), polymers as drag-reducing additives have been widely used to reduce the undesired drag that occurs over long-distance transportation of liquids. However, less attention has been focused on this area of research, especially in the case of re circulating flow systems. This is mainly due to the fact that the polymer additive’s capability as a drag reducer can be permanently crippled when subjected to high shear rates or exposed to prolonged period of turbulent flow and repeated heating and cooling. In contrast to the polymer additives, mechanical degradation of surfactant additives when exposed to regions of high shear stress or repeated heating and cooling is only temporary. In the present study, a two-dimensional water tunnel was designed and fabricated to investigate drag reduction by surfactant additives. Flow development check experiments were performed with different concentrations of surfactant additives to justify the fully developed flow conditions at the test section. The results indicate that the hydrodynamic entry length for water flow without surfactants is very short. For surfactant concentrations of 20, 60, 120 and 160 ppm, the entry lengths were about 300, 500, 1200 and 1400 mm respectively. The entry length for the surfactant concentration of 200 ppm was consistent with that of 160 ppm. Dilute surfactant solutions at different concentration were used to examine the influence of surfactant additives on the skin friction drag and heat transfer. RG 13/02 2010-11-02T07:44:56Z 2010-11-02T07:44:56Z 2007 2007 Research Report http://hdl.handle.net/10356/42324 en 168 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Mechanical engineering
spellingShingle DRNTU::Engineering::Mechanical engineering
Zhou, Tongming.
Nguyen, Nam Trung.
Leong, Kai Choong.
Smart control of drag reduction and heat transfer in a channel flow
description Since the discovery of the Toms effect (Toms, 1948), polymers as drag-reducing additives have been widely used to reduce the undesired drag that occurs over long-distance transportation of liquids. However, less attention has been focused on this area of research, especially in the case of re circulating flow systems. This is mainly due to the fact that the polymer additive’s capability as a drag reducer can be permanently crippled when subjected to high shear rates or exposed to prolonged period of turbulent flow and repeated heating and cooling. In contrast to the polymer additives, mechanical degradation of surfactant additives when exposed to regions of high shear stress or repeated heating and cooling is only temporary. In the present study, a two-dimensional water tunnel was designed and fabricated to investigate drag reduction by surfactant additives. Flow development check experiments were performed with different concentrations of surfactant additives to justify the fully developed flow conditions at the test section. The results indicate that the hydrodynamic entry length for water flow without surfactants is very short. For surfactant concentrations of 20, 60, 120 and 160 ppm, the entry lengths were about 300, 500, 1200 and 1400 mm respectively. The entry length for the surfactant concentration of 200 ppm was consistent with that of 160 ppm. Dilute surfactant solutions at different concentration were used to examine the influence of surfactant additives on the skin friction drag and heat transfer.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Zhou, Tongming.
Nguyen, Nam Trung.
Leong, Kai Choong.
format Research Report
author Zhou, Tongming.
Nguyen, Nam Trung.
Leong, Kai Choong.
author_sort Zhou, Tongming.
title Smart control of drag reduction and heat transfer in a channel flow
title_short Smart control of drag reduction and heat transfer in a channel flow
title_full Smart control of drag reduction and heat transfer in a channel flow
title_fullStr Smart control of drag reduction and heat transfer in a channel flow
title_full_unstemmed Smart control of drag reduction and heat transfer in a channel flow
title_sort smart control of drag reduction and heat transfer in a channel flow
publishDate 2010
url http://hdl.handle.net/10356/42324
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