Abstract
A finite difference analysis of the entrance region flow heat transfer of Herschel-Bulkley fluids in concentric annuli with rotating inner wall has been carried out. The analysis is made for simultaneously developing hydrodynamic and thermal boundary layer in concentric annuli with one wall being isothermal and other one being adiabatic. The inner cylinder is assumed to be rotating with a constant angular velocity and the outer cylinder being stationary. A finite difference analysis is used to obtain the velocity distributions, pressure drop and temperature variations along the radial direction. Computational results are obtained for various values of aspect ratio, flow index, Prandtl’s number and Herschel-Bulkley number. Comparison of the present results with the results available in literature for various particular cases has been done and found to be in agreement.
Highlights
The study of non-Newtonian laminar flow heat transfer in thermal entrance region of an annuli is of practical importance in engineering applications such as design of compact heat exchangers, axial-flow turbo machinery and polymer processing industries
In case of turbulent flow, when heating starts at the duct entrance, the hydrodynamic boundary layers normally are linear near the duct entrance and the transitions to turbulence occurs at some distance downstream from the entrance
Numerical calculations have been performed for all admissible values of aspect ratio N, flow index n, Prandtl's number and Herschel-Bulkley number
Summary
The study of non-Newtonian laminar flow heat transfer in thermal entrance region of an annuli is of practical importance in engineering applications such as design of compact heat exchangers, axial-flow turbo machinery and polymer processing industries. Sayed-Ahmed and Hazem [5] have applied finite difference method to study the laminar flow of a Power-Law fluid in the concentric annuli with rotating inner wall. Kandasamy et al [10] investigated the entrance region flow of heat transfer in concentric annuli for Herschel Bulkley fluids and presents the velocity distributions, temperature and pressure in the entrance region. Kandasamy and Srinivasa Rao [12], [13] have investigated the entrance region flow in concentric annuli with rotating inner wall for Herschel Bulkley and Bingham fluids. The problem of entrance region flow heat transfer of Herschel-Bulkley fluids in concentric annuli has been investigated. The development of axial velocity profile, radial velocity profile, tangential velocity profile, pressure drop and temperature variations in the entrance region have been determined for different values of nonNewtonian flow characteristics and geometrical parameters. The effects of these on the temperature variations have been discussed
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