Analysis of the flow characteristic inside a heated and unheated horizontal rifled tube
Rifled tube which is one of the rough surface tube has been getting attention from researchers due to its ability to enhance the heat transfer. Previous researches on rifled tube has been done through experimental work. Therefore, numerical analysis by using commercial Computational Fluid Dyna...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2012
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/2465/1/24p%20SOO%20POEY%20LAM.pdf http://eprints.uthm.edu.my/2465/2/SOO%20POEY%20LAM%20WATERMARK.pdf |
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| Summary: | Rifled tube which is one of the rough surface tube has been getting attention from
researchers due to its ability to enhance the heat transfer. Previous researches on
rifled tube has been done through experimental work. Therefore, numerical analysis
by using commercial Computational Fluid Dynamics (CFD), Fluent® has been
carried out to investigate the flow characteristic of the single phase flow in 2 meters
long of horizontally rifled tube and smooth tube under heating condition and without
heating condition at the outer wall. The rifled tube or also known as spiral internally
ribbed tube that is used in this investigation has an outside diameter 45.0 mm and
inside equivalent diameter of 33.1 mm while the smooth tube has an outside diameter
45 mm and inside diameter 34.1 mm. The working fluid that is used in this
investigation is water. In this numerical analysis, realizable k-epsilon model has been
chosen to solve the fully developed turbulence flow in the rifled tube and smooth
tube. The result of the numerical analysis showed that there was swirling effect at the
near-wall-region for both the case of the rifled tube under heating condition and
without heating condition at the wall. The flow characteristic of the rifled tube in
terms of pressure drop when there is no heat flux condition at the outer wall shows
that the pressure drop in rifled tube is 1.69 – 1.77 folds than in the smooth tube.
Meanwhile, when there is heating at the wall of the tubes, the pressure drop and heat
transfer coefficient in rifled tube are about 1.67-2.0 times and 0.97-1.27 times
respectively, than in smooth tube. The high pressure drop and Nusselt number in
rifled tube is due to the helical rib in the rifled tube which not only has disturbed the
flow but also causes swirling effect near the wall. As a result, the heat transfers from
the wall to the flow near the wall region is enhanced. The present study also has
proved that although the rifled tube produces high pressure drop but it is good in heat
transfer enhancement through the ratio of heat flux to the pumping power. |
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