Numerical Investigation of Power-Law Fluid Flows and Heat Transfer inside of Curved Duct under Aiding Thermal Buoyancy

2018 ◽  
Vol 16 ◽  
pp. 84-95 ◽  
Author(s):  
Fayçal Bouzit ◽  
Houssem Laidoudi ◽  
Bilal Blissag ◽  
Mohamed Bouzit ◽  
Abdellah Guenaim
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Power Law ◽  
Flow Behavior ◽  
Two Dimensions ◽  
Thermal Buoyancy ◽  
Curved Duct ◽  
Ansys Cfx ◽  
Power Law Fluids ◽  
Power Law Index

This paper deals with a numerical investigation in order to predict correctly the combined effects of aiding thermal buoyancy and rheological flow behavior of power-law fluids on downward flow and heat transfer rate inside of 180° curved duct. The governing equations involving the momentum, continuity and the energy are solved in two-dimensions using the package called ANSYS-CFX. The computational results are depicted and discussed for the range of conditions as:Re= 40 to 1000,Ri= 0 to-1 andn= 0.4 to 1.2 at fixed value of Prandt number ofPr= 1. To interpret the found results, the flow structure and temperature field are shown in form of streamlines and isotherm contours. The average Nusselt number of the inner and outer walls of curved channel is calculated to determine the role of Reynolds number, Richardson number and power-law index. It is found that increase in strength of aiding buoyancy creates a counter rotating region in angle of 90 degrees of the duct.

Simulation of Non Newtonian Power-Law Fluid Flows and Mixed Convection Heat Transfer inside of Curved Duct

2017 ◽  
Vol 378 ◽  
pp. 113-124 ◽  
Author(s):  
Bouzit Fayçal ◽  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Power Law ◽  
Transfer Rate ◽  
Richardson Number ◽  
Flow Behavior ◽  
Thermal Buoyancy ◽  
Flow And Heat Transfer ◽  
Curved Duct ◽  
Power Law Fluids

A two-dimensional numerical simulation is carried out to understand the combined effects of thermal buoyancy strength and rheological flow behavior of non Newtonian power-law fluids on laminar flow and heat transfer rate through a 180° curved duct. The governing equations including the full Navier-Stokes, the continuity and the energy are solved using the commercial code ANSYS-CFX. The numerical results are presented and discussed for the range of conditions as: Re = 40 to 1000, Ri = 0 to 1 and n = 0.4 to 1.2 for fixed value of Prandt number of Pr = 1. In order to analyze the obtained results, the representative streamlines and isotherm patterns are presented. The average Nusselt number of the inner and outer walls of duct is computed to determine the role of Reynolds number, Richardson number and power-law index on flow and heat transfer. It is found that increase in Richardson number creates alternative vortices on duct walls. Moreover, the alternative vortices enhance the heat transfer rate for shear thinning, Newtonian and shear thickening fluids.

Non-Newtonian Power-Law Flows around Circular Cylinder under Aiding/Opposing Thermal Buoyancy

2018 ◽  
Vol 16 ◽  
pp. 45-56
Author(s):  
Houssem Laidoudi ◽  
Mohamed Bouzit
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Power Law ◽  
Flow Separation ◽  
Vertical Channel ◽  
Buoyancy Effect ◽  
Thermal Buoyancy ◽  
Power Law Fluids ◽  
Recirculation Length ◽  
Power Law Index

This paper presents a comprehensive computational work on hydrodynamic and thermal phenomena of upward flow separation around a confined circular cylinder by aiding/opposing thermal buoyancy. For that purpose, let us consider a confined flow of Non-Newtonian power-law fluid around a heated/cooled circular cylinder in a two-dimensional vertical channel. The effects of thermal buoyancy and power-Law index on the flow separation and the average Nusselt number are studied for the conditions: (10 ≤ Re ≤ 40), (0.4≤ n ≤ 1.2), (-0.5 ≤ Ri ≤ 0.8), Pr = 50 and blockage ratio β = 0.2. In the steady flow regime the results show that the augmentation of the power-law index in the absence of thermal buoyancy causes a separation to grow. The adding buoyancy effect delays the separation in different power-law indices gradually and at some critical value of the buoyancy parameter it completely disappears resulting a stuck flow around a cylinder, whereas the opposing buoyancy effect causes an earlier wake behind cylinder. Moreover, the recirculation length is calculated to support the above finding. The decrease in the power-Law index increases the heat transfer rate. The Nusselt numbers are computed to predict the heat transfer rates of power-law fluids under the aiding/opposing thermal buoyancy condition.

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.

Numerical Simulation for Heat Transfer of Nanofluid in a Rotating Circular Groove Using a Continuous Finite Element Scheme

2014 ◽  
Vol 1081 ◽  
pp. 175-179 ◽  
Author(s):  
Yong Yue Jiang ◽  
Ping Lin ◽  
Bo Tong Li ◽  
Lin Li
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Power Law ◽  
Initial Time ◽  
The Finite Element Method ◽  
Finite Element Scheme ◽  
Element Scheme ◽  
Circular Groove ◽  
Power Law Fluids ◽  
Power Law Index

In this paper, we investigate the heat transfer of the power-law-fluids-based nanofluids in a rotating circular groove. The circular groove rotates with a constant speed and the temperature on the wall of the groove is different from the temperature inside in the initial time. The effects of thermophoresis and Brownian are considered. The thermal conductivity of the nanofluids is taken as a constant. We solve the model with the finite element method directly and discretize them using a continuous finite element scheme in space and a modified midpoint scheme in time. From the results we can find that the heat transfer enhancement of the nanofluids increases as the power law index of the base fluid decreases.

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.

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.

Numerical Investigation of Natural Convection Heat Transfer From an Array of Horizontal Fins in Non-Newtonian Power-Law Fluids

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Jacob K. Mulamootil ◽  
Sukanta K. Dash
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Power Law ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Flat Plates ◽  
Power Law Fluids ◽  
Power Law Index ◽  
Fin Length

Natural convection heat transfer from an array of horizontal rectangular fins on a vertical flat plate in non-Newtonian power-law fluids has been studied. The underlying physical principles affecting heat transfer were studied using comprehensive solutions obtained from numerical investigations. Heat transfer to the power-law fluid was found to depend on the fluid rheology (power-law index) and significantly on the geometric parameters (interfin spacing, fin length) as well. The dependence was quantified using the Nusselt number (Nu) and fin effectiveness (Q/Q0). The present study shows that compared to a fin analyzed in isolation, the spatial arrangement of multiple fins relative to one another in an array does have a significant effect on the flow field around subsequent fins in power-law fluids. Therefore, the average heat transfer coefficient of the natural convection system is affected significantly. The variation of Nu with the dimensionless fin length (l/L), dimensionless interfin spacing (S/L), and fluid power-law index (n) was plotted. The dependence was found to be counter intuitive to expectations based on studies for natural convection from vertical flat plates to power-law fluids. In the present study involving fins, shear-thinning fluids (n < 1) show a decrease in heat transfer and shear-thickening fluids (n > 1) show an enhancement in heat transfer for higher l/L values. The results of the study may be useful in the design of natural convection systems that employ power-law fluids to enhance or control heat transfer.

Lattice Boltzmann Modelling for Natural Convection in Power-Law Fluids within a Partially Heated Square Enclosure

2020 ◽  
Author(s):  
Siva Subrahmanyam Mendu ◽  
P.K. Das
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Heat Source ◽  
Power Law ◽  
Lattice Boltzmann ◽  
Collision Term ◽  
Square Enclosure ◽  
Power Law Fluids ◽  
Power Law Index

Abstract The present paper reports the numerical investigations for steady-state natural convection in power-law fluids inside a square enclosure embedded with bottom discrete heaters. The Lattice Boltzmann Method (LBM) is employed to model the flow and heat transfer phenomenon at different combinations of power-law index, Rayleigh number, and heat source length for a constant Prandtl number. The buoyancy force is incorporated in the collision term of the LBM through Boussinesq approximation. Simulation outcomes are furnished using streamlines and, temperature contours, velocity profiles and variation of heat transfer on the non-adiabatic walls to probe natural convection phenomena. The results indicate that the temperature and the flow fields in the enclosure are symmetric about the vertical centerline. The detailed physical interpretations have been provided for the reported results. Further, the increase in the power-law index means a rise in viscosity and a decrease in thermal energy transport for other constant parameters. The outcomes also specify that the intensity of circulation and heat transfer enhances with the increase of Rayleigh number and size of the localized heater. Finally, though, a rise in the size of the confined heat source enhances the rate of total thermal transport, it does not change the trend of fluid flow and local heat transfer rate.

scholarly journals Fluid Flow and Heat Transfer in Power-Law Fluids Across Circular Cylinders: Analytical Study

2005 ◽  
Author(s):  
Waqar A. Khan ◽  
Richard J. Culham ◽  
Milan M. Yovanovich
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Integral Equation ◽  
Power Law ◽  
Circular Cylinders ◽  
Integral Approach ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Power Law Fluids ◽  
Power Law Index

An integral approach of the boundary layer analysis is employed for the modeling of fluid flow around and heat transfer from infinite circular cylinders in power-law fluids. The Von Karman-Pohlhausenmethod is used to solve the momentum integral equation whereas the energy integral equation is solved for both isothermal and isoflux boundary conditions. A fourth-order velocity profile in the hydrodynamic boundary layer and a third-order temperature profile in the thermal boundary layer are used to solve both integral equations. Closed form expressions are obtained for the drag and heat transfer coefficients that can be used for a wide range of the power-law index, and generalized Reynolds and Prandtl numbers. It is found that pseudoplastic fluids offer less skin friction and higher heat transfer coefficients than dilatant fluids. As a result, the drag coefficients decrease and the heat transfer increases with the decrease in power-law index. Comparison of the analytical models with available experimental/numerical data proves the applicability of the integral approach for power-law fluids.

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