Effect of Power-Law Fluid Behavior on Nusselt Number of a Circular Disk in the Forced Convection Regime

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
P. Mishra ◽  
S. A. Patel ◽  
M. Trivedi ◽  
R. P. Chhabra
Keyword(s):  
Nusselt Number ◽  
Forced Convection ◽  
Power Law ◽  
Average Nusselt Number ◽  
Creeping Flow ◽  
Constant Wall Temperature ◽  
Fluid Behavior ◽  
Power Law Fluids ◽  
Wide Range ◽  
Power Law Index

Forced convection heat transfer is investigated from a thin disk in power-law fluids over wide range of conditions such as: Reynolds number, 1 ≤ Re ≤ 100, Prandtl number, 1 ≤ Pr ≤ 100, power-law index, 0.4 ≤ n ≤ 1.8, and disk thickness to diameter ratio, t/D = 0.01, 0.025, 0.05, and 0.075. The wide range of values of the power-law index spanned here covers both shear-thinning as well as shear-thickening fluid behavior. These results also elucidate the influence of the type of thermal boundary conditions, i.e., constant wall temperature condition (CWT) and constant heat flux condition (CHF) prescribed on the disk surface. Extensive results are presented in terms of the local and average Nusselt numbers to delineate the effect of each of the influencing parameters, Re, Pr, n, t/D for each thermal boundary condition. Limited results are also included here at vanishingly small values of the Peclet number to understand the behavior in the creeping flow condition. Finally, the present numerical results on the average Nusselt number have been consolidated in the form of a predictive equation to facilitate the interpolation of the present data for intermediate values of the parameters and/or a priori estimation of the average Nusselt number in a new application.

Forced Convection in Cross Flow of Power Law Fluids Over a Pair of Circular Cylinder in Tandem Arrangement

2008 ◽  
Author(s):  
Rahul C. Patil ◽  
Ram P. Bharti ◽  
Raj P. Chhabra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Forced Convection ◽  
Power Law ◽  
Average Nusselt Number ◽  
Cross Flow ◽  
Heat Transfer Characteristics ◽  
Tandem Arrangement ◽  
Transfer Characteristics ◽  
Power Law Fluids

Forced convection heat transfer characteristics for the flow of incompressible power law fluids over a pair of cylinders (of equal diameters) in tandem arrangement have been studied numerically in the two-dimensional, steady cross-flow regime. The field equations have been solved using a finite volume method based solver (FLUENT 6.2) over the ranges of conditions as follows: power law index (n = 0.4, 1, 1.8), Reynolds number (Re = 1, 40), Prandtl number (Pr = 1, 100), the gap between the two cylinders (G = 2) and for two thermal boundary conditions, namely constant temperature or heat flux prescribed on the surface of the two cylinders. While the upstream cylinder shows heat transfer characteristics similar to that of an isolated cylinder, the downstream cylinder displays a complex dependence on the relevant dimensionless parameters. Both the wake interference and power-law rheology influence the heat transfer characteristics to varying extents. Generally, the upstream cylinder shows higher values of the average Nusselt number than the downstream cylinder. However, the average Nusselt number values for both cylinders are seen to be smaller than that for a single cylinder otherwise under identical conditions. With reference to Newtonian fluids, the shear-thinning behaviour promotes heat transfer whereas shear-thickening lowers it.

Heat Transfer in Fully Developed Laminar Flow of Power Law Fluids

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
A. Baptista ◽  
M. A. Alves ◽  
P. M. Coelho
Keyword(s):  
Nusselt Number ◽  
Laminar Flow ◽  
Viscous Dissipation ◽  
Power Law ◽  
Numerical Solutions ◽  
Constant Heat Flux ◽  
Parallel Plates ◽  
Constant Wall Temperature ◽  
Power Law Fluids ◽  
Wide Range

In this work, we present approximate and exact solutions for the temperature profile and Nusselt number under fully developed laminar flow of a power law fluid inside pipes and between parallel plates. Constant wall temperature and negligible axial heat conduction are considered, for both the cases with and without viscous dissipation. For completeness, the corresponding solutions for the related problem of constant heat flux at the wall are also presented. In the absence of viscous dissipation, the solutions obtained are semi-analytic, since they rely upon an iterative procedure. As a benchmark result, to allow comparison with the results obtained with the semi-analytical expressions, we also present highly accurate numerical solutions for the Nusselt number, Nu, based on numerical integration of the energy equation. Also based on these numerical results, simplified correlations for Nu are proposed, valid for a wide range of the power law index.

Forced convection heat transfer study of a blunt-headed cylinder in non-Newtonian power-law fluids

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jaspinder Kaur ◽  
Roderick Melnik ◽  
Anurag Kumar Tiwari
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Power Law ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Total Drag ◽  
Shear Thinning Fluids ◽  
Power Law Fluids

Abstract In this present work, forced convection heat transfer from a heated blunt-headed cylinder in power-law fluids has been investigated numerically over the range of parameters, namely, Reynolds number (Re): 1–40, Prandtl number (Pr): 10–100 and power-law index (n): 0.3–1.8. The results are expressed in terms of local parameters, like streamline, isotherm, pressure coefficient, and local Nusselt number and global parameters, like wake length, drag coefficient, and average Nusselt number. The length of the recirculation zone on the rear side of the cylinder increases with the increasing value of Re and n. The effect of the total drag coefficient acting on the cylinder is seen to be higher at the low value of Re and its effect significant in shear-thinning fluids (n < 1). On the heat transfer aspect, the rate of heat transfer in fluids is increased by increasing the value of Re and Pr. The effect of heat transfer is enhanced in shear-thinning fluids up to ∼ 40% and it impedes it’s to ∼20% shear-thickening fluids. In the end, the numerical results of the total drag coefficient and average Nusselt number (in terms of J H −factor) have been correlated by simple expression to estimate the intermediate value for the new application.

Unsteady Forced Convection Heat Transfer for Power Law Fluids in a Pipe

2010 ◽  
Author(s):  
Botong Li ◽  
Liancun Zheng ◽  
Xinxin Zhang
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Power Law ◽  
Control Volume ◽  
Convection Heat Transfer ◽  
Inlet Temperature ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Power Law Fluids ◽  
Power Law Index

This paper studied the problem of forced convection heat transfer for power law fluids in a pipe which was affected by the varying inlet temperature. The fluid flow was hydrodynamically fully-developed and laminar while the effects of viscous dissipation and the power law kinematic viscosity on heat transfer were considered. A control volume technique based on the finite difference model coupled with the LU decomposition method was adopted and the least squares polynomial was introduced to approximate the non-linear items. The results show that the heat transfer behaviors are strongly depending on the value of the power law index. It is found that the thermal wave of the inlet temperature has less penetration with the increasing axial coordinate, and the effect of heat transfer is dominant away from the wall. The temperature profile is flatter as the power law index increases, which is implies that the shear-thickening non-Newtonian flows are affected easier by the inlet temperature than the shear-thinning fluids.

scholarly journals Numerical Analysis and Entropy Generation of Electrokinetic Flow of Power-Law Fluid in a Microtriangular Prism

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Fehaid Salem Alshammari
Keyword(s):  
Nusselt Number ◽  
Entropy Generation ◽  
Power Law ◽  
Second Law Of Thermodynamics ◽  
Physical Parameters ◽  
Electrokinetic Flow ◽  
Power Law Fluids ◽  
Transfer Equations ◽  
Constant Wall Heat Flux ◽  
Power Law Index

This research aims to study the characteristics of thermal transport and analyse the entropy generation of electroosmotic flow of power-law fluids in a microtriangular prism in the presence of pressure gradient. Considering a fully developed flow subject to constant wall heat flux, the nonlinear electric potential, momentum, and linear heat transfer equations are solved numerically by developing an iterative finite difference method with a nonuniform grid. The thermal efficiency of the model is explored under the light of the second law of thermodynamics. Effect/impact of governing physical parameters on velocity, temperature, Nusselt number, and entropy distributions is studied, and the results are demonstrated graphically; we found that the Nusselt number decreases with the increase of power-law index, and average entropy generation increases with power-law index. We believe that the obtained result in the present study shall be useful for design of energy efficient microsystems which utilize the dual electrokinetic and centrifugal pumping effects.

Mixed Convection From a Heated Square Cylinder to Newtonian and Power-Law Fluids

2006 ◽  
Vol 129 (4) ◽  
pp. 506-513 ◽  
Author(s):  
A. K. Dhiman ◽  
N. Anjaiah ◽  
R. P. Chhabra ◽  
V. Eswaran
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Mixed Convection ◽  
Power Law ◽  
Richardson Number ◽  
Square Cylinder ◽  
Laminar Mixed Convection ◽  
Power Law Fluids ◽  
Power Law Index

Steady laminar mixed convection flow and heat transfer to Newtonian and power-law fluids from a heated square cylinder has been analyzed numerically. The full momentum and energy equations along with the Boussinesq approximation to simulate the buoyancy effects have been solved. A semi-explicit finite volume method with nonuniform grid has been used for the range of conditions as: Reynolds number 1–30, power-law index: 0.8–1.5, Prandtl number 0.7–100 (Pe⩽3000) for Richardson number 0–0.5 in an unbounded configuration. The drag coefficient and the Nusselt number have been reported for a range of values of the Reynolds number, Prandtl number, and Richardson number for Newtonian, shear-thickening (n>1) and shear-thinning (n<1) fluids. In addition, detailed streamline and isotherm contours are also presented to show the complex flow field, especially in the rear of the cylinder. The effects of Prandtl number and of power-law index on the Nusselt number are found to be more pronounced than that of buoyancy parameter (Ri⩽0.5) for a fixed Reynolds number in the steady cross-flow regime (Re⩽30).

Natural Convection Heat Transfer of Non-Newtonian Power-Law Fluids Within an Array of Elliptic Cylinders

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
A. Torkfar ◽  
S. M. A. Noori Rahim Abadi ◽  
A. Ahmadpour
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Power Law ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Mathematical Expression ◽  
Numerical Results ◽  
Temperature Fields ◽  
Single Cylinder ◽  
Power Law Fluids

Abstract In this study, natural convection of non-Newtonian power-law fluids around an array of elliptic cylinders has been investigated numerically. The governing equations have been solved using an in-house computational fluid dynamics code based on the well-known finite volume method. It is assumed that the flow and temperature fields are laminar, steady, and two-dimensional. Furthermore, due to the low-temperature difference between the tube walls and the surrounding fluid, the changes in the physical properties of the fluids are neglected. The numerical results are validated against the available experimental and numerical results. The results show that by increasing the non-Newtonian fluid power-law index, the ratio of average Nusselt number of the ith cylinder to the average Nusselt number of a single cylinder under identical thermal conditions decreases. Moreover, it is found that the increase in the ratio of the distance between elliptic centers and the elliptic vertical diameter increases the ratio of the average Nusselt number of ith cylinder to the average Nusselt number for a single cylinder. Finally, a mathematical expression is given for the array averaged Nusselt number.

Mixed Convection Heat Transfer from a Heated Square Cylinder Immersed in Upward Flow of Power-Law Fluids

2018 ◽  
Vol 16 ◽  
pp. 72-83
Author(s):  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Power Law ◽  
Convection Heat Transfer ◽  
Creeping Flow ◽  
Temperature Fields ◽  
Square Cylinder ◽  
Thermal Buoyancy ◽  
Power Law Fluids ◽  
Recirculation Length ◽  
Power Law Index

This paper examines the effects of thermal buoyancy on momentum and heat transfer characteristics of confined square cylinder submerged in incompressible power-law fluid. The detailed flow and temperature fields are visualized in terms of streamlines and isotherm contours. The numerical results have been presented and discussed for the range of conditions as (10 ≤Re≤ 40), Richardson number (0 ≤Ri≤ 1), and power-law index (0.4 ≤n≤ 1.2) at Prandtl numberPr= 50, at fixed value of blockage ratioβ= 25%. The results showed that the augmentation of the power-law index in the absence of thermal buoyancy causes a separation to diminish for the valueRe= 40. The thermal buoyancy delays the flow separation in different power-law indexes gradually and at some critical value of the buoyancy parameter it completely disappears resulting a creeping flow around a cylinder. Moreover, the recirculation length and skin friction are calculated to support the above finding. The decrease in the power-Law index promotes the heat transfer rate. The Nusselt numbers are computed to predict the heat transfer rates of power-law fluids under the superimposed thermal buoyancy condition.

Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

2021 ◽  
pp. 095440622110272
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Litan Kumar Saha ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

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