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1

Effect of aiding buoyancy on heat transfer from an isothermal square cylinder in power-law fluids

Mishra Pragya, Mishra Lubhani, Tiwari Anurag Kumar

Chemical and Process Engineering

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2022

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Vol. 43, nr 2

265–-270

EN

The aim of the present study was to explore the influence of aiding buoyancy on mixed convection heat transfer in power-law fluids from an isothermally heated unconfined square cylinder. Extensive numerical results on drag coefficient and surface averaged values of the Nusselt number are reported over a wide range of parameters i.e. Richardson number, 01 Ri 5, power-law index, 04 𝑛 18, Reynolds number, 01 Re 40, and Prandtl number, 1 Pr 100. Further, streamline profiles and isotherm contours are presented herein to provide an insight view of the detailed flow kinematics

2

Behaviour of a non-newtonian fluid in a helical tube under the influence of thermal buoyancy

Ramla Mohamed, Laidoudi Houssem, Bouzit Mohamed

Acta Mechanica et Automatica

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2022

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Vol. 16, no. 2

111--118

EN

This work is an evaluative study of heat transfer in the helical-type heat exchanger. The fluid used is non-Newtonian in nature and is defined by Oswald’s model. The work was performed numerically by solving each of the Navier–Stokes equations and the energy equation using the package ANSYS-CFX. Following are the aspects that have been dealt with in this paper: the effects of thermal buoyan-cy, fluid nature and the tube shape on the heat transfer, and the fluid comportment. The interpretation of the obtained results was done by analyzing the isotherms and the streamlines. The mean values of the Nusselt number were also obtained in terms of the studied parame-ters. The results of this research enabled us to arrive at the following conclusion: the intensity of thermal buoyancy and the nature of the fluid affect the heat transfer distribution but keep the overall rate of heat transfer the same.

3

Investigation of velocity profile in time dependent boundary layer flow of a modified power-law fluid of fourth grade

Yurusoy M.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 2

176--191

EN

This paper deals with the investigation of time dependent boundary layer flow of a modified power-law fluid of fourth grade on a stretched surface with an injection or suction boundary condition. The fluid model is a mixture of fourth grade and power-law fluids in which the fluid may display shear thickening, shear thinning or normal stress textures. By using the scaling and translation transformations which is a type of Lie Group transformation, time dependent boundary layer equations are reduced into two alternative ordinary differential equations systems (ODEs) with boundary conditions. During this reduction, special Lie Group transformations are used for translation, scaling and combined transformation. Numerical solutions have been carried out for the ordinary differential equations for various fluids and boundary condition parameters. As a result of numerical analysis, it is observed that the boundary layer thickness decreases as the power-law index value increases. It was also observed that for the fourth-grade fluid parameter, as the parameter increases, the boundary layer thickness decreases while the velocity in the y direction increases.

4

Patel M., Timol M. G.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 4

1205-1214

EN

A steady three dimensional MHD free convection and mass transfer flow past a semi-infinite surface in the presence of heat generation has been studied numerically for non-Newtonian power law fluids. The governing partial differential equations are reduced to a system of an ordinary differential equation using similarity transformation.

5

Viscous heating in rotational viscometer - maximum shear rate determination

Rieger F.

Czasopismo Techniczne. Mechanika

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2008

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R. 105, z. 2-M

311-316

EN

The present paper deals with viscous heating of liquid in rotational viscometer with coaxial cylinders, which is often used for measurement of rheological behaviour. Due to viscous energy dissipation the temperature of measured liquid can be considerably higher than tempering temperature, which can lead to significant experimental error. For this reason the maximum shear rate corresponding to acceptable maximum temperature difference should be controlled.

PL

Niniejsza praca dotyczy lepkiego nagrzewania się cieczy w reometrze rotacyjnym o współosiowych cylindrach, który często stosowany jest do pomiaru własności reologicznych. W wyniku lepkiego rozproszenia energii temperatura badanej cieczy może być istotnie wyższa od pierwotnej temperatury układu, co prowadzić może do znacznych błędów pomiaru. Dlatego należy kontrolować maksymalną szybkość ścinania związaną z maksymalną dopuszczalną różnicą temperatur.

6

Thermal dispersion effects on non-Darcy axisymmetric free convection in a porous medium saturated with a non-Newtonian fluid

El-Amin M. F.

International Journal of Applied Mechanics and Engineering

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2005

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Vol. 10, no 1

77-86

EN

A boundary layer analysis is presented to study the effects of thermal dispersion of a non-Newtonian fluid on non-Darcy axisymmetric free convection over a horizontal surface embedded in a porous medium. The Ostwald-de-Waele power-law model is used to characterize the non-Newtonian fluid behavior. The thermal diffusivity coefficient has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. Similarity solutions are obtained when the surface temperature varies as the square root of the radial distance (i.e., the prescribed temperature PT) or when heat flux is constant (i.e., the prescribed heat flux PHF). The effects of the dispersion and non-Darcy parameters as well as the power-law index n on the velocity, temperature, the Nusselt number and the boundary layer thickness are shown on graphs. The numerical values of the rate of heat transfer through the boundary layer in terms of the Nusselt number are entered in a table.