Flow Inertia and Heat Transfer in Suddenly Expanding Annular Shear-Thinning Flows

2017 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Power Law ◽  
Shear Thinning ◽  
Heat Transfer Augmentation ◽  
Flow And Heat Transfer ◽  
Prandtl Numbers ◽  
Power Law Index ◽  
Annular Pipe ◽  
Flow Inertia ◽  
The Impact

The impact of flow inertia on flow and heat transfer in suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid is studied within the steady laminar flow regime. The equations governing conservation of mass, momentum, and energy, along with the power-law constitutive model are numerically solved using a finite-difference numerical scheme. The influence of inflow inertia, annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers, is reported for: Re = {50, 100}, k = {0, 0.5}; n = {1, 0.6}; and Pr = {1, 10, 100}. Heat transfer augmentation, downstream the plane of expansion, is only observed for Pr = 10 and 100. The extent and intensity of recirculation in the corner region, increases with inflow inertia. Higher Reynolds and Prandtl numbers, power-law index values, and annular diameter ratios, in general, reflect a more dramatic heat transfer augmentation downstream of the expansion plane.

Heat Transfer Enhancement in Annular Shear-Thinning Flows Over a Sudden Pipe Expansion

2017 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Power Law ◽  
Shear Thinning ◽  
Diameter Ratio ◽  
Transfer Enhancement ◽  
Heat Transfer Augmentation ◽  
Prandtl Numbers ◽  
Power Law Index ◽  
The Impact

Heat transfer enhancement in suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid is studied within the steady laminar flow regime. Conservation of mass, momentum, and energy equations, along with the power-law constitutive model are numerically solved. The impact of inflow inertia, annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers, is reported for: Re = {50, 100}, k = {0, 0.5, 0.7}; n = {1, 0.8, 0.6}; and Pr = {1, 10, 100}. Heat transfer enhancement downstream of the expansion plane, i.e., Nusselt numbers, Nu, higher than the fully developed value, in the downstream pipe, is observed only for Pr = 10 and 100. Higher Prandtl numbers, power-law index values, and annular diameter ratios, in general, reflect a more dramatic heat transfer augmentation downstream of the expansion plane. Heat transfer augmentation for Pr = 10 and 100, is more dramatic for suddenly expanding annular flows, in comparison with suddenly expanding pipe flow. For a given annular diameter ratio and Reynolds numbers, increasing the Prandtl number from Pr = 10 to Pr = 100, always results in higher peak Nu values, for both Newtonian and shear-thinning non-Newtonian flows.

Inflow Conditions and Heat Transfer From Suddenly Expanding Annular Pseudoplastic Flows

2017 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Power Law ◽  
Pseudoplastic Fluid ◽  
Transfer Rates ◽  
Inflow Condition ◽  
Prandtl Numbers ◽  
Power Law Index ◽  
Annular Pipe ◽  
The Impact ◽  
Inflow Conditions

The impact of inflow conditions on flow and heat transfer in suddenly expanding annular pipe flows of a pseudoplastic fluid is studied within the steady laminar flow regime. The equations governing conservation of mass, momentum, and energy, along with the power-law constitutive model are numerically solved using a finite-difference numerical scheme. The influence of inflow conditions, annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers, is reported for: Inflow Condition = {fully-developed, uniform}; κ = {0, 0.5}; n = {1, 0.6}; Re = {50}; Pr = {1, 10, 100}. Fully-developed inflows result in larger and more intense recirculation, which leads to higher wall heat transfer rates, in comparison with uniform inflows. Substantial heat transfer augmentation, downstream the plane of expansion, is only observed for Pr = 10 and 100.

Heat Transfer in Annular Shear-Thinning Non-Newtonian Flows Over a Sudden Pipe Expansion

2016 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Power Law ◽  
Shear Thinning ◽  
Wall Heat Transfer ◽  
Transfer Enhancement ◽  
Transfer Rates ◽  
Newtonian Flows ◽  
Prandtl Numbers ◽  
Annular Pipe

Non-isothermal suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid are numerically studied within the steady laminar flow regime. The power-law constitutive equation is used to model the shear-thinning rheology of interest. A parametric study is performed to reveal the influence of annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers over the following range of parameters: k = {0, 0.5}; n = {1, 0.6}; and Pr = {1, 10, 100}. Heat transfer enhancement, i.e., wall heat transfer rates higher than the fully developed ones downstream of the expansion plane, is observed only for Pr = 10 and 100. In the case of Pr = 1, wall heat transfer rates monotonically increase to the fully developed value. Higher Pr, k, and n values, in general, result in more significant heat transfer enhancement downstream of the expansion plane. Further, shear-thinning non-Newtonian flows display two local peak wall heat transfer rates, in comparison with only one peak value in the case of Newtonian flows.

Developing and Fully Developed Non-Newtonian Fluid Flow and Heat Transfer Through Concentric Annuli

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Mohammad Sefid ◽  
Ehsan Izadpanah
Keyword(s):  
Heat Transfer ◽  
Power Law ◽  
Convection Heat Transfer ◽  
Channel Length ◽  
Laminar Flows ◽  
Rheological Parameter ◽  
Power Law Fluid ◽  
Thermal Boundary Conditions ◽  
Flow And Heat Transfer ◽  
Power Law Index

Developing and fully developed laminar flows of power law fluid with forced convection heat transfer through a concentric annular duct are numerically analyzed. The results are presented for the following ranges: 0.2 ≤ n ≤ 1.8 (power law index), 10 ≤ Re ≤ 1000 (Reynolds number), and r* = 0.2, 0.5, 0.8 (aspect ratio). In addition, the influences of different thermal boundary conditions on the thermal performance are delineated. The effects of rheological parameter on the developing length, friction factor, temperature distribution, velocity profile, and Nusselt number along the channel length are investigated. The results are compared with earlier research and excellent agreement was observed.

Computational Modeling of Enhanced Laminar Flow Heat Transfer in Viscoplastic Fluids in Corrugated-Plate Channels

2002 ◽  
Author(s):  
Hossam M. Metwally ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Yield Stress ◽  
Power Law ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Bingham Plastic ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Colburn Factor ◽  
Power Law Index

The enhanced heat transfer in laminar viscoplastic, shear thinning, Herschel-Bulkley fluid flows in sinusoidal corrugated-plate channels is investigated. With uniform-temperature plate walls, periodically developed flows are considered for a wide range of flow rates (10 ≤ Reg ≤ 700) and pseudoplastic flow behavior indices (n = 0.54, 0.8, and 1.0; the latter representing a Bingham plastic). The effects of fluid yield stress are simulated for the case where τy = 1.59 N/m2, representing a 0.5% xantham gum aqueous solution. Typical velocity and temperature distributions, along with extended results for isothermal friction factor ƒ and Colburn factor j are presented. The effect of the yield stress is found to be most dominant at low Reg regardless of the power law index n, and the recirculation or swirl in the wall trough regions is weaker than in the cases of Newtonian and power-law liquids. At higher Reg, the performance of the Herschel-Bulkley fluid asymptotically approaches that of the non-yield-stress power-law fluid. At low Reg, the yield stress increases ƒ by an order of magnitude and j is enhanced because of the higher wall gradients imposed by the plug-like flow field. The relative heat transfer enhancement, represented by the ratio (j/ƒ), and the role of the fluid yield stress and shear-thinning (or pseudoplastic) behaviors are also discussed.

scholarly journals Slip-Flow and Heat Transfer in a Porous Microchannel Saturated with Power-Law Fluid

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Yazan Taamneh ◽  
Reyad Omari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Skin Friction ◽  
Knudsen Number ◽  
Power Law ◽  
Slip Flow ◽  
Darcy Number ◽  
Power Law Fluid ◽  
Flow And Heat Transfer ◽  
Power Law Index

This study aims to numerically examine the fluid flow and heat transfer in a porous microchannel saturated with power-law fluid. The governing momentum and energy equations are solved by using the finite difference technique. The present study focuses on the slip flow regime, and the flow in porous media is modeled using the modified Darcy-Brinkman-Forchheimer model for power-law fluids. Parametric studies are conducted to examine the effects of Knudsen number, Darcy number, power law index, and inertia parameter. Results are given in terms of skin friction and Nusselt number. It is found that when the Knudsen number and the power law index decrease, the skin friction on the walls decreases. This effect is reduced slowly while the Darcy number decreases until it reaches the Darcy regime. Consequently, with a very low permeability the effect of power law index vanishes. The numerical results indicated also that when the power law index decreases the fully-developed Nusselt number increases considerably especially, in the limit of high permeability, that is, nonDarcy regime. As far as Darcy regime is concerned the effects of the Knudsen number and the power law index of the fully-developed Nusselt number is very little.

Inflow Conditions and Suddenly Expanding Annular Shear-Thinning Flows

2017 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Power Law ◽  
Numerical Solutions ◽  
Shear Thinning ◽  
Diameter Ratio ◽  
Inflow Velocity ◽  
Flow Recirculation ◽  
Shear Thinning Fluids ◽  
Power Law Index ◽  
The Impact ◽  
Inflow Conditions

The impact of inflow conditions on the flow structure and evolution characteristics of annular flows of Newtonian and shear-thinning fluids through a sudden pipe expansion are studied. Numerical solutions to the elliptic form of the governing equations along with the power-law constitutive equation were obtained using a finite-difference scheme. A parametric study is performed to reveal the influence of inflow velocity profiles, annular diameter ratio, k, and power-law index, n, over the following range of parameters: inflow velocity profile = {fully-developed, uniform}, k = {0, 0.5, 0.7} and n = {1, 0.8, 0.6}. Flow separation and entrainment, downstream of the expansion plane, creates central and a much larger outer recirculation regions. The results demonstrate the influence of inflow conditions, annular diameter ratio, and rheology on the extent and intensity of both flow recirculation regions, the wall shear stress distribution, and the evolution and redevelopment characteristics of the flow downstream the expansion plane. Fully-developed inflows result in larger reattachment and redevelopment lengths as well as more intense recirculation, within the central and corner regions, in comparison with uniform inflow conditions.

Transverse magnetic flow over a Reiner–Philippoff nanofluid by considering solar radiation

2019 ◽  
Vol 33 (36) ◽  
pp. 1950449 ◽  
Author(s):  
M. Gnaneswara Reddy ◽  
Sudha Rani ◽  
K. Ganesh Kumar ◽  
Asiful H. Seikh ◽  
Mohammad Rahimi-Gorji ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Transverse Magnetic ◽  
Surface Drag ◽  
Transfer Rates ◽  
Heat Transfer Augmentation ◽  
Flow And Heat Transfer ◽  
Plastic Fluid ◽  
Dilatant Fluid ◽  
The Impact ◽  
Linear Radiation

This paper reports the flow and heat transfer augmentation on Reiner–Philippoff nanofluid over stretching sheet. The effect of transverse magnetic field and thermal radiation are explored for temperature distributions. Transformations are used to reduce system of partial differential equations into ordinary ones and are solved numerically by using RKF-45 Method. Expressions for velocity and temperature profile are derived and plotted under the assumption of flow parameter. Influence of various parameters on surface drag force and heat transfer rates have been discussed with the help of tables and plots. It is noticed that the impact of pseudo plastic fluid, Newtonian fluid and dilatant fluid are highly contrasted in higher Ha. Furthermore, production of heat transfer is more in nonlinear radiation when compared to linear radiation.

MHD Flow of Shear-Thinning Fluid over a Rotating Disk with Heat Transfer

2011 ◽  
Vol 130-134 ◽  
pp. 3599-3602
Author(s):  
Chun Ying Ming ◽  
Lian Cun Zheng ◽  
Xin Xin Zhang
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Power Law ◽  
Swirling Flow ◽  
Mhd Flow ◽  
Rotating Disk ◽  
Electrically Conducting ◽  
Flow And Heat Transfer ◽  
Power Law Index ◽  
Shear Thinning Fluid

This paper studied the Magneto hydrodynamic (MHD) flow and heat transfer of an electrically conducting non-Newtonian fluid over a rotating disk in the presence of a uniform magnetic field. The steady, laminar and axial-symmetric flow is driven solely by the rotating disk, and the incompressible fluid obeys the inelastic Ostwald de-Waele power-law model. The governing differential equations were reduced to a set of ordinary differential equations by utilizing the generalized Karman similarity transformation. The nonlinear two-point boundary value problem is solved by multi-shooting method. Numerical results show that the magnetic parameter and the power-law index have significant effects on the swirling flow and heat transfer.

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