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Author(s)
Md. Mamun Molla, Department of Mathematics & Physics, North South University, Dhaka, Bangladesh.
S. Ghosh Moulic, Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur, Kharagpur 721302, India
LunShin Yao, School for Engineering of Matter, Transport and Energy, Arizona State University, Arizona, 85287, USA.
Abstract
Fullydeveloped forced convection heat transfer of a pseudoplastic fluid in a uniformly heated circular tube has been studied. The model used is a modification of the twoparameter Ostwaldde Waele power law, which correctly represents the upper and lower regions of Newtonian behavior shown by pseudoplastic or shearthinning polymer melts and solutions. Results for a shearthinning polymer solution, for which experimental data for the apparent viscosity is available over a large range of shearrate magnitudes, predicted using the modified powerlaw viscosity model, have been presented. A new nondimensional shearrate parameter governing the flow has been identified. The nonNewtonian fluid mechanics community has been unaware of the existence of this parameter. The paradox in the prediction of boundary layer flows caused by lack of knowledge of this parameter has been well documented by our previous studies. In this paper, we discuss it for nonboundarylayer flows. The momentum and energy equations have been solved numerically, for fully developed pipe flow, by the trapezoidal rule and finite volume method respectively. The results indicate that there are three regimes of flow. When the shearrate parameter is small, the fluid behaves like a Newtonian fluid and the Nusselt number is identical to that for a Newtonian fluid. At intermediate values of the shearrate parameter, there are two regions of flow: a central region where the fluid behaves like a Newtonian fluid and an outer region where the fluid behaves like a powerlaw fluid. The Nusselt numbers predicted by the modified power law and power law models agree in this intermediate range of shear rates. When the shearrate parameter is large, there are two Newtonian regions, one near the axis and one near the wall, with a middle powerlaw zone.
Keywords
NonNewtonian fluid, modified powerlaw, forced convection heat transfer, Boger’s experimental data
Cite this paper
Md. Mamun Molla,
S. Ghosh Moulic,
LunShin Yao,
Prediction of Heat Transfer to Fully Developed Pipe Flows with a Modified Power Law Viscosity Model, SCIREA Journal of Mechanics. Vol.
1
, No.
1
,
2016
, pp.
1

47
.
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