Thermal Optimization of an Internally Finned Tube Using Analytical Solutions Based on a Porous Medium Approach

2007 ◽  
Vol 129 (10) ◽  
pp. 1408-1416 ◽  
Author(s):  
Kyu Hyung Do ◽  
Jung Yim Min ◽  
Sung Jin Kim
Keyword(s):  
Porous Medium ◽  
Analytical Solutions ◽  
Saturated Porous Medium ◽  
Equation Model ◽  
Finned Tube ◽  
Navier Stokes ◽  
Uniform Heat Flux ◽  
Thermal Optimization ◽  
Internally Finned Tube ◽  
Cylindrical Region

The present work deals with thermal optimization of an internally finned tube having axial straight fins with axially uniform heat flux and peripherally uniform temperature at the wall. The physical domain was divided into two regions: One is the central cylindrical region of the fluid extending to the tips of the fins and the other constituted the remainder of the tube area. The latter region including the fins was modeled as a fluid-saturated porous medium. The Brinkman-extended Darcy equation for fluid flow and two-equation model for heat transfer were used in the porous region, while the classical Navier–Stokes and energy equations were used in the central cylindrical region. The analytical solutions for the velocity and temperature profiles were in close agreement with the corresponding numerical solution as well as with existing theoretical and experimental data. Finally, optimum conditions, where the thermal performance of the internally finned tube is maximized, were determined using the developed analytical solutions.

Thermal Optimization of a Circular-Sectored Finned Tube Using a Porous Medium Approach

2002 ◽  
Vol 124 (6) ◽  
pp. 1026-1033 ◽  
Author(s):  
Sung Jin Kim ◽  
Jae Wook Yoo ◽  
Seok Pil Jang
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Fluid Flow ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Effective Conductivity ◽  
Saturated Porous Medium ◽  
Finned Tube ◽  
Uniform Heat Flux ◽  
Total Thermal Resistance

The present work investigates the heat transfer characteristics of a laminar fully developed forced convection in a circular-sectored finned tube with axially uniform heat flux and peripherally uniform wall temperature. The tubes with circular-sectored fins are modeled as a fluid-saturated porous medium. Using the Brinkman-extended Darcy model for fluid flow and the two-equation model for heat transfer, the analytical solutions for both velocity and temperature distributions are obtained and compared with the exact solution for fluid flow and the numerical solutions for conjugate heat transfer in order to validate the porous medium approach. The agreement between the solutions based on the porous medium approach and the conventional method is close within 5.3 percent. Based on the analytical solutions, parameters of engineering importance are identified to be the angle of the circular sector α and the effective conductivity ratio C, and their effects on fluid flow and heat transfer are studied. Also, the total thermal resistance is derived from the analytical solutions and minimized in order to optimize the thermal performance of a tube with circular-sectored fins.

scholarly journals Development of An Integrated Numerical Model for Simulating Wave Interaction with Permeable Submerged Breakwaters Using Extended Navier–Stokes Equations

2020 ◽  
Vol 8 (2) ◽  
pp. 87 ◽  
Author(s):  
Paran Pourteimouri ◽  
Kourosh Hejazi
Keyword(s):  
Porous Medium ◽  
Wave Propagation ◽  
Numerical Model ◽  
Analytical Solutions ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Stokes Wave ◽  
Navier Stokes Equations ◽  
Numerical Predictions ◽  
The Impact

An integrated two-dimensional vertical (2DV) model was developed to investigate wave interactions with permeable submerged breakwaters. The integrated model is capable of predicting the flow field in both surface water and porous media on the basis of the extended volume-averaged Reynolds-averaged Navier–Stokes equations (VARANS). The impact of porous medium was considered by the inclusion of the additional terms of drag and inertia forces into conventional Navier–Stokes equations. Finite volume method (FVM) in an arbitrary Lagrangian–Eulerian (ALE) formulation was adopted for discretization of the governing equations. Projection method was utilized to solve the unsteady incompressible extended Navier–Stokes equations. The time-dependent volume and surface porosities were calculated at each time step using the fraction of a grid open to water and the total porosity of porous medium. The numerical model was first verified against analytical solutions of small amplitude progressive Stokes wave and solitary wave propagation in the absence of a bottom-mounted barrier. Comparisons showed pleasing agreements between the numerical predictions and analytical solutions. The model was then further validated by comparing the numerical model results with the experimental measurements of wave propagation over a permeable submerged breakwater reported in the literature. Good agreements were obtained for the free surface elevations at various spatial and temporal scales, velocity fields around and inside the obstacle, as well as the velocity profiles.

Thermal Viscous Dissipative Couette Flow in a Porous Medium Filled Microchannel

2016 ◽  
Author(s):  
Farrukh Mirza Baig ◽  
G. M. Chen ◽  
B. K. Lim
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Nusselt Number ◽  
Couette Flow ◽  
Viscous Dissipation ◽  
Saturated Porous Medium ◽  
Local Thermal Equilibrium ◽  
Uniform Heat Flux ◽  
Brinkman Number ◽  
Essential Information

The increasing demand for high-performance electronic devices and surge in power density accentuates the need for heat transfer enhancement. In this study, a thermal viscous dissipative Coeutte flow in a micochannel filled with fluid saturated porous medium is looked into. The study explores the fluid flow and heat transfer phenomenon for a Coeutte flow in a microchannel as well as to establish the relationship between the heat convection coefficient and viscous dissipation. The moving boundary in this problem is subjected to uniform heat flux while the fixed plate is assumed adiabatic. In order to simplify the problem, we consider a fully developed flow and assume local thermal equilibrium in the analysis. An analytical Nusselt number expression is developed in terms of Brinkman number as a result of this study, thus providing essential information to predict accurately the thermal performance of a microchannel. The results obtained without viscous dissipation are in close agreement with published results whereas viscous dissipation has a more significant effect on Nusselt number for a porous medium with higher porous medium shape factor. The Nusselt number versus Brinkman number plot shows an asymptotic Brinkman number, indicating a change in sign of the temperature difference between the bulk mean temperature and the wall temperature. The effects of Reynolds number on the two dimensional temperature profile for a Couette flow in a microchannel are investigated. The temperature distribution of a microscale duct particularly along the axial direction is a strong function of viscous dissipation. The significance of viscous dissipation to a microscale duct as compared to a conventional scale duct is also discussed and compared in this study.

Forced convection in a fluid-saturated porous-medium channel with isothermal or isoflux boundaries

1996 ◽  
Vol 322 ◽  
pp. 201-214 ◽  
Author(s):  
D. A. Nield ◽  
S. L. M. Junqueira ◽  
J. L. Lage
Keyword(s):  
Porous Medium ◽  
Forced Convection ◽  
Saturated Porous Medium ◽  
Practical Importance ◽  
Isothermal Condition ◽  
Convection Heat Transfer ◽  
Momentum Equation ◽  
Uniform Heat Flux ◽  
Parallel Plates ◽  
Fluid Saturated Porous Medium

We present a fresh theoretical analysis of fully developed forced convection in a fluid-saturated porous-medium channel bounded by parallel plates, with imposed uniform heat flux or isothermal condition at the plates. As a preliminary step, we obtain an ‘exact’ solution of the Brinkman-Forchheimer extension of Darcy's momentum equation for flow in the channel. This uniformly valid solution permits a unified treatment of forced convection heat transfer, provides the means for a deeper explanation of the physical phenomena, and also leads to results which are valid for highly porous materials of current practical importance.

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