Characteristics of Fully Developed Flow and Heat Transfer in Channels With Varying Wall Geometry

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Abhishek G. Ramgadia ◽  
Arun K. Saha
Keyword(s):  
Heat Transfer ◽  
Time Dependent ◽  
Navier Stokes ◽  
Fully Developed Flow ◽  
Flow And Heat Transfer ◽  
Collocated Grid ◽  
Wall Profile ◽  
Energy Equations ◽  
Volume Method ◽  
Wall Geometry

Present study focuses on numerical investigation of fully developed flow and heat transfer through three channels having sine-shaped, triangle-shaped, and arc-shaped wall profiles. All computations are performed at Reynolds number of 600. Finite volume method on collocated grid is used to solve the time-dependent Navier–Stokes and energy equations in primitive variable form. For all the geometries considered in the study, the ratios Hmin/Hmax and L/a are kept fixed to 0.4 and 8.0, respectively. The thermal performances of all the three wall configurations are assessed using integral parameters as well as instantaneous, time-averaged and fluctuating flow fields. The geometry with the sinusoidal-shaped wall profile is found to produce the best thermal properties as compared to the triangle-shaped and the arc-shaped profiles though the obtained heat transfer is the highest for the arc-shaped geometry.

Effect of Inclination Angle on Three-Dimensional Combined Convective Heat Transfer of Nanofluids in Rectangular Channels

2013 ◽  
Vol 388 ◽  
pp. 176-184
Author(s):  
Hussein A. Mohammed ◽  
Nur Irmawati Om ◽  
Mazlan A. Wahid
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Inclination Angle ◽  
Pure Water ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Rectangular Channels ◽  
Energy Equations ◽  
Volume Method

Combined convective nanofluids flow and heat transfer in an inclined rectangular duct is numerically investigated. Three dimensional, laminar Navier-Stokes and energy equations were solved using the finite volume method. Pure water and four types of nanofluids such as Au, CuO, SiO2 and TiO2with volume fractions range of 2% φ 7% are used. This investigation covers the following ranges: 2 × 106 Ra 2 × 107, 100 Re 1000 and 30° Θ 60°. The results revealed that the Nusselt number increased as Rayleigh number increased.SiO2nanofluid has the highest Nusselt number while Au nanofluid has the lowest Nusselt number. An increasing of the duct inclination angle decreases the heat transfer.

Axisymmetric Stagnation-Point Flow and Heat Transfer of a Viscous Fluid on a Moving Cylinder With Time-Dependent Axial Velocity and Uniform Transpiration

2004 ◽  
Vol 126 (6) ◽  
pp. 997-1005 ◽  
Author(s):  
R. Saleh ◽  
A. B. Rahimi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Axial Velocity ◽  
Time Dependent ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Moving Cylinder ◽  
Self Similar ◽  
Suction Rate ◽  
Axial Speed

The unsteady viscous flow and heat transfer in the vicinity of an axisymmetric stagnation point of an infinite moving cylinder with time-dependent axial velocity and with uniform normal transpiration Uo are investigated. The impinging free stream is steady and with a constant strain rate k¯. An exact solution of the Navier–Stokes equations and energy equation is derived in this problem. A reduction of these equations is obtained by use of appropriate transformations for the most general case when the transpiration rate is also time-dependent but results are presented only for uniform values of this quantity. The general self-similar solution is obtained when the axial velocity of the cylinder and its wall temperature or its wall heat flux vary as specified time-dependent functions. In particular, the cylinder may move with constant speed, with exponentially increasing–decreasing axial velocity, with harmonically varying axial speed, or with accelerating–decelerating oscillatory axial speed. For self-similar flow, the surface temperature or its surface heat flux must have the same types of behavior as the cylinder motion. For completeness, sample semisimilar solutions of the unsteady Navier–Stokes and energy equations have been obtained numerically using a finite-difference scheme. Some of these solutions are presented for special cases when the time-dependent axial velocity of the cylinder is a step-function, and a ramp function. All the solutions above are presented for Reynolds numbers, Re=ka¯2/2υ, ranging from 0.1 to 100 for different values of dimensionless transpiration rate, S=Uo/ka¯, where a is cylinder radius and υ is kinematic viscosity of the fluid. Absolute value of the shear-stresses corresponding to all the cases increase with the increase of Reynolds number and suction rate. The maximum value of the shear- stress increases with increasing oscillation frequency and amplitude. An interesting result is obtained in which a cylinder moving with certain exponential axial velocity function at any particular value of Reynolds number and suction rate is axially stress-free. The heat transfer coefficient increases with the increasing suction rate, Reynolds number, Prandtl number, oscillation frequency and amplitude. Interesting means of cooling and heating processes of cylinder surface are obtained using different rates of transpiration. It is shown that a cylinder with certain type of exponential wall temperature exposed to a temperature difference has no heat transfer.

Axisymmetric Stagnation—Point Flow and Heat Transfer of a Viscous Fluid on a Rotating Cylinder With Time-Dependent Angular Velocity and Uniform Transpiration

2006 ◽  
Vol 129 (1) ◽  
pp. 106-115 ◽  
Author(s):  
A. B. Rahimi ◽  
R. Saleh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Angular Velocity ◽  
Stokes Equations ◽  
Time Dependent ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer ◽  
Self Similar

The unsteady viscous flow and heat transfer in the vicinity of an axisymmetric stagnation point of an infinite rotating circular cylinder with transpiration U0 are investigated when the angular velocity and wall temperature or wall heat flux all vary arbitrarily with time. The free stream is steady and with a strain rate of Γ. An exact solution of the Navier-Stokes equations and energy equation is derived in this problem. A reduction of these equations is obtained by the use of appropriate transformations for the most general case when the transpiration rate is also time-dependent but results are presented only for uniform values of this quantity. The general self-similar solution is obtained when the angular velocity of the cylinder and its wall temperature or its wall heat flux vary as specified time-dependent functions. In particular, the cylinder may rotate with constant speed, with exponentially increasing/decreasing angular velocity, with harmonically varying rotation speed, or with accelerating/decelerating oscillatory angular speed. For self-similar flow, the surface temperature or its surface heat flux must have the same types of behavior as the cylinder motion. For completeness, sample semi-similar solutions of the unsteady Navier-Stokes equations have been obtained numerically using a finite-difference scheme. Some of these solutions are presented for special cases when the time-dependent rotation velocity of the cylinder is, for example, a step-function. All the solutions above are presented for Reynolds numbers, Re=Γa2∕2υ, ranging from 0.1 to 1000 for different values of Prandtl number and for selected values of dimensionless transpiration rate, S=U0∕Γa, where a is cylinder radius and υ is kinematic viscosity of the fluid. Dimensionless shear stresses corresponding to all the cases increase with the increase of Reynolds number and suction rate. The maximum value of the shear stress increases with increasing oscillation frequency and amplitude. An interesting result is obtained in which a cylinder rotating with certain exponential angular velocity function and at particular value of Reynolds number is azimuthally stress-free. Heat transfer is independent of cylinder rotation and its coefficient increases with the increasing suction rate, Reynolds number, and Prandtl number. Interesting means of cooling and heating processes of cylinder surface are obtained using different rates of transpiration.

Heat Transfer Study of Staggered Thin Rectangular Blocks in a Channel Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 294-300 ◽  
Author(s):  
Ching Jen Chen ◽  
Ramiro H. Bravo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Channel Flow ◽  
Vector Fields ◽  
Block Size ◽  
Navier Stokes ◽  
Maximum Heat ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Energy Equations

In this study, fluid flow and heat transfer in two-dimensional staggered thin rectangular blocks in a channel flow heat exchanger is analyzed by the Finite Analytic Numerical Method. The heat exchanger consists of four staggered thin rectangular blocks at temperature T1 placed inside a channel which is formed by two plates maintained at constant temperature T0. The fluid is considered to be incompressible and the flow laminar. Flow and heat transfer from the inlet of the heat exchanger to the outlet are simulated by solving Navier-Stokes and energy equations. Results were obtained for different block spacing and different size of the blocks. Computations were made for Reynolds numbers 100, 500, and 1,000, and Prandtl numbers 0.7 and 4.0. The results are presented in the form of velocity vector fields, isotherms, and local and global Nusselt numbers. The characteristics of the heat transfer and pressure drop in different block size and block separation are analyzed. The optimal length of separation between thin blocks and the optimal block length for maximum heat transfer are determined.

scholarly journals Numerical Computation of Turbulent Flow and Heat Transfer in a Radially Rotating Channel with Wall Conduction

2001 ◽  
Vol 7 (3) ◽  
pp. 209-222
Author(s):  
Frank K. T. Lin ◽  
G. J. Hwang ◽  
S.-C. Wong ◽  
C. Y. Soong
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Computation ◽  
Experimental Models ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Turbine Blade Cooling ◽  
Flow And Heat Transfer ◽  
Energy Equations ◽  
Rotating Channel

This work is concerned with numerical computation of turbulent flow and heat transfer in experimental models of a radially rotating channel used for turbine blade cooling. Reynolds-averaged Navier-Stokes and energy equations with a two-layer turbulence model are employed as the computational model of the flow and temperature fields. The computations are carried out by the software package of “CFX-TASCflow”. Heat loss from the channel walls through heat conduction is considered. Results at various rotational conditions are obtained and compared with the baseline stationary cases. The influences of the channel rotation, through-flow, wall conduction and the channel extension on flow and heat transfer characteristics are explored. Comparisons of the present predictions and available experimental data are also presented.

scholarly journals Investigation of Two-Dimensional Unsteady Stagnation-Point Flow and Heat Transfer Impinging on an Accelerated Flat Plate

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Ali Shokrgozar Abbassi ◽  
Asghar Baradaran Rahimi
Keyword(s):  
Heat Transfer ◽  
Strain Rate ◽  
Flat Plate ◽  
Stagnation Point ◽  
Stagnation Point Flow ◽  
Navier Stokes ◽  
Variable Velocity ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Energy Equations

General formulation and solution of Navier–Stokes and energy equations are sought in the study of two-dimensional unsteady stagnation-point flow and heat transfer impinging on a flat plate when the plate is moving with variable velocity and acceleration toward main stream or away from it. As an application, among others, this accelerated plate can be assumed as a solidification front which is being formed with variable velocity. An external fluid, along z-direction, with strain rate a impinges on this flat plate and produces an unsteady two-dimensional flow in which the plate moves along z-direction with variable velocity and acceleration in general. A reduction of Navier–Stokes and energy equations is obtained by use of appropriate similarity transformations. Velocity and pressure profiles, boundary layer thickness, and surface stress-tensors along with temperature profiles are presented for different examples of impinging fluid strain rate, selected values of plate velocity, and Prandtl number parameter.

Unsteady Flow and Heat Transfer Characteristics of Fluid Flow Over a Shrinking Permeable Infinite Long Cylinder

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Emad J. Elnajjar ◽  
Qasem M. Al-Mdallal ◽  
Fathi M. Allan
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Navier Stokes ◽  
Suction Parameter ◽  
Similarity Transformations ◽  
Flow And Heat Transfer ◽  
Runge Kutta Method ◽  
Method Of Solution ◽  
Energy Equations ◽  
Long Cylinder

The present work studies the unsteady, viscous, and incompressible laminar flow and heat transfer over a shrinking permeable cylinder. The unsteady nonlinear Navier–Stokes and energy equations are reduced, using similarity transformations, to a system of nonlinear ordinary differential equations. The boundary conditions associated with the governing equations are the time dependent surface temperature and flow conditions. The method of solution is based on a combination of the implicit Runge–Kutta method and the shooting method. The present study predicts two solutions for both the flow and heat transfer fields, and a unique solution at a specific critical unsteadiness parameter. An analysis of the results, for a specific suction parameter, suggests that the corresponding unique unsteadiness parameter does not depend on the Prandtl number. However, the unique rate of heat transfer is increasing as the Prandtl number increases. In addition, our results confirm that the unique value of heat transfer rate increases as the suction parameter increases, regardless the value of the Prandtl number.

scholarly journals Numerical study on characteristics of flow and thermal fields around rotating cylinder

10.30544/450 ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 71-86
Author(s):  
Kamel Korib ◽  
Mohamed ROUDANE ◽  
Yacine Khelili
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Study ◽  
Simple Algorithm ◽  
Rotation Rates ◽  
Rotating Circular Cylinder ◽  
Flow And Heat Transfer ◽  
Lift And Drag ◽  
Energy Equations ◽  
Volume Method

In this paper, a numerical simulation has been performed to study the fluid flow and heat transfer around a rotating circular cylinder over low Reynolds numbers. Here, the Reynolds number is 200, and the values of rotation rates (α) are varied within the range of 0 < α < 6. Two-dimensional and unsteady mass continuity, momentum, and energy equations have been discretized using the finite volume method. SIMPLE algorithm has been applied for solving the pressure linked equations. The effect of rotation rates (α) on fluid flow and heat transfer were investigated numerically. Also, time-averaged (lift and drag coefficients and Nusselt number) results were obtained and compared with the literature data. A good agreement was obtained for both the local and averaged values.

Numerical Computation of Fluid Flow and Heat Transfer in Microchannels

2005 ◽  
Author(s):  
Ningli Liu ◽  
Rene Chevray ◽  
Gerald A. Domoto ◽  
Elias Panides
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Energy Equation ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Time Dependent ◽  
Navier Stokes ◽  
Temperature Profiles ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer

A finite difference numerical approach for solving slightly compressible, time-dependent, viscous laminar flow is presented in this study. Simplified system of Navier-Stokes equations and energy equation are employed in the study in order to perform more efficient numerical calculations. Fluid flow and heat transfer phenomena in two dimensional microchannels are illustrated numerically in this paper. This numerical approach provides a complete numerical simulation of the development of the fluid flow and the temperature profiles through multi-dimensional microchannels.

The Effect of Triangular Vortex Generators on Turbulent Flow and Heat Transfer in a Channel

2010 ◽  
Author(s):  
Hosseinali Soltanipour ◽  
Iraj Mirzaei ◽  
Parisa Choupani
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Rectangular Channel ◽  
Vortex Generators ◽  
Navier Stokes ◽  
Single Element ◽  
Longitudinal Vortices ◽  
Energy Equations ◽  
Volume Method ◽  
Physical Phenomena

In the present work heat transfer characteristics and flow structure in turbulent flow through a rectangular channel containing built-in triangular winglet-type vortex generators have been analyzed by means of solutions of the Navier-Stokes and energy equations using finite volume method. The geometrical configuration is representative of single element of plain-plate heat exchangers. Each winglet-pair induces longitudinal vortices behind it. Shear stress transport (SST) model is used in this study. The underlying physical phenomena have been described and the effects of Reynolds number and angle of attack, on the heat transfer, pressure drop and thermal performance have been presented.

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