Lord Kelvin and Weaire–Phelan Foam Models: Heat Transfer and Pressure Drop

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Salvatore Cunsolo ◽  
Marcello Iasiello ◽  
Maria Oliviero ◽  
Nicola Bianco ◽  
Wilson K. S. Chiu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Complex Geometry ◽  
Thermal Characteristics ◽  
Metallic Foams ◽  
Surface Evolver ◽  
Promising Tool ◽  
Numerical Predictions ◽  
Energy Equations ◽  
Lord Kelvin

The knowledge of thermal transport characteristics is of primary importance in the application of foams. The thermal characteristics of a foam heavily depend on its microstructure and, therefore, have to be investigated at a pore level. However, this analysis is a challenging task, because of the complex geometry of a foam. The use of foam models is a promising tool in their study. The Kelvin and the Weaire–Phelan foam models, among the most representative practical foam models, are used in this paper to numerically investigate heat transfer and pressure drop in metallic foams. They are developed in the “surface evolver” open source software. Mass, momentum, and energy equations, for air forced convection in open cell foams, are solved with a finite-element method, for different values of cell size and porosity. Heat transfer and pressure drop results are reported in terms of volumetric Nusselt number and Darcy–Weisbach friction factor, respectively. Finally, a comparison between the numerical predictions obtained with the two foam models is carried out, in order to evaluate the feasibility to substitute the more complex and computationally heavier Weaire–Phelan foam structure with the simpler Kelvin foam representation. Negligible differences between the two models are exhibited at high porosities.

Microtomography-Based Analysis of Pressure Drop and Heat Transfer Through Open Cell Metal Foams

2013 ◽  
Author(s):  
M. Oliviero ◽  
S. Cunsolo ◽  
W. M. Harris ◽  
M. Iasiello ◽  
W. K. S. Chiu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Thermal Characteristics ◽  
Industrial Applications ◽  
Metal Foams ◽  
Surface Evolver ◽  
Periodic Cell ◽  
Numerical Predictions

Their light weight, open porosity, high surface area per unit volume and thermal characteristics make metal foams a promising material for many industrial applications involving fluid flow and heat transfer. Pressure drop and heat transfer of porous media have inspired a number of experimental and numerical studies. Many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models. Most studies are based on idealized periodic cell structures. In this study, the true 3-D micro-structure of the metal foam is obtained by employing x-ray computed microtomography (XCT). For comparison, ideal Kelvin foam structures are developed in the free-to-use software “Surface Evolver” surface energy minimization program. Pressure drop and heat transfer are then investigated using the CFD Module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out.

scholarly journals Heat transfer analysis of nanofluid flow through backward facing step

2020 ◽  
Vol 307 ◽  
pp. 01010 ◽  
Author(s):  
Ahlem Boudiaf ◽  
Fetta Danane ◽  
Youb Khaled Benkahla ◽  
Walid Berabou ◽  
Mahdi Benzema ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Thermal Characteristics ◽  
Heat Transfer Analysis ◽  
Backward Facing Step ◽  
Nanofluid Flow ◽  
Numerical Predictions ◽  
Flow Through ◽  
Volume Method

This paper presents the numerical predictions of hydrodynamic and thermal characteristics of nanofluid flow through backward facing step. The governing equations are solved through the finite volume method, as described by Patankar, by taking into account the associated boundary conditions. Empirical relations were used to give the effective dynamic viscosity and the thermal conductivity of the nanofluid. Effects of different key parameters such as Reynolds number, nanoparticle solid volume fraction and nanoparticle solid diameter on the heat transfer and fluid flow are investigated. The results are discussed in terms of the average Nusselt number and streamlines.

Analysis of Enhanced Heat Transfer on a Turbine Blade Tip-Wall With and Without Guide Ribs

2010 ◽  
Author(s):  
Gongnan Xie ◽  
Bengt Sunde´n ◽  
Weihong Zhang ◽  
Esa Utriainen ◽  
Lieke Wang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbine Blade ◽  
Turbulent Heat Transfer ◽  
Channel Height ◽  
Turbulent Heat ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Numerical Predictions ◽  
Blade Tip

Cooling methods are needed for gas turbine blade tips that are exposed to high temperature gas. A common way to cool the blade and its tip is to design serpentine passages with 180-deg turn under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip lifetime. This paper presents numerical predictions of turbulent heat transfer through two-pass channels with and without guide ribs (guide vanes) placed in the turn regions using RANS turbulence modeling. The effects of adding guide ribs on the tip-wall heat transfer enhancement and the channel pressure drop have been analyzed. The inlet Reynolds numbers are ranging from 100,000 to 600,000, and the rib cross-section blockage ratio (rib height to channel height, 2e/H) is 0.182. The detailed fluid flow and heat transfer over the tip-wall are presented. The overall performances of three two-pass channels are evaluated and compared. It is found that the tip heat transfer coefficients of the channels with guide ribs are 20%∼50% higher than that of a channel without guide ribs. The presence of guide ribs could lead to an increased (about 15%) or decreased (up to about 12%) pressure drop, depending upon the geometry and placement of guide ribs. It is suggested that the usage of guide ribs is a suitable way to improve the flow structure and augment the blade tip heat transfer, but is not the most effective way to augment tip-wall heat transfer compared to the augmentation by surface modifications imposed on the tip directly.

Thermal Anisotropy in Injection Molded Polymer Composite Fins

2010 ◽  
Author(s):  
Avram Bar-Cohen ◽  
Patrick Luckow ◽  
Juan G. Cevallos ◽  
S. K. Gupta
Keyword(s):  
Heat Transfer ◽  
Polymer Composite ◽  
Thermal Characteristics ◽  
Axial Direction ◽  
Transfer Coefficients ◽  
Thermal Anisotropy ◽  
Modeling Methodology ◽  
Numerical Predictions ◽  
Injection Molded ◽  
Global And Local

An integrated molding-heat transfer modeling methodology is used to study the thermal characteristics of polymer composite fins subjected to convective heat transfer coefficients. Numerical predictions of the fiber orientation in a representative, injection-molded plate fin, based on the Folgar-Tucker model, are used, via the classic Nielsen model, to determine the anisotropic variation of thermal conductivity in the fin. Thermal simulations are then performed to determine the effect of both global and local thermal anisotropy on the temperature distribution and heat transfer rate of the anisotropic fin. It is also shown that the harmonic mean conductivity, in the axial direction, can be used to represent the heat loss of an anisotropic fin to better than 10% accuracy.

Scrutiny the Heat Transfer Effect in an Annulus by Mounting Axial Fins with Different Shapes: Without and with Taylor Number

2021 ◽  
Vol 409 ◽  
pp. 142-157
Author(s):  
Farouk Kebir ◽  
Youcef Attou
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Annular Channel ◽  
Reynolds Stress Model ◽  
Taylor Number ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Rsm Model ◽  
Energy Equations ◽  
The Impact

This study aimed to investigate numerically the heat transfer improvement and pressure drop inside annular channel of a rotor-stator provided with fins mounted on the stator without and with Taylor number. The impact of mounting various types of fins (triangular, rectangular, trapezoidal shapes with small and large base) is studied by varying the fin width b from 0 to 14 mm. In the presence of axial air flow, numerical simulations are carried out by solving the governing continuity, momentum and energy equations of turbulent flow in cylindrical coordinates using the Finite Volume Method. The results obtained by Reynolds Stress Model RSM model have indicated that the heat transfer enhances as the surface area of the fins and the effective Reynolds number increase, while there is an increase in pressure drop. Furthermore, we have shown that the presence of Taylor number has a slight increase in Nusselt number and pressure drop compared to the case without Taylor number. Among the four geometries, it is found that the rectangular cavity is the best geometry which gives maximum heat transfer and minimum pressure loss.

Numerical Analysis of Heat Transfer and Pressure Drop in Metal Foams for Different Morphological Models

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Marcello Iasiello ◽  
Salvatore Cunsolo ◽  
Maria Oliviero ◽  
William M. Harris ◽  
Nicola Bianco ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Industrial Applications ◽  
Metal Foams ◽  
The Real ◽  
Numerical Predictions ◽  
The Ideal

Because of their light weight, open porosity, high surface area per unit volume, and thermal characteristics, metal foams are a promising material for many industrial applications involving fluid flow and heat transfer. The pressure drop and heat transfer in porous media have inspired a number of experimental and numerical studies, and many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models, and most studies are based on idealized periodic cell structures. In this study, the true three-dimensional microstructure of the metal foam is obtained by employing x-ray computed microtomography (XCT). This is the “real” structure. For comparison, ideal Kelvin foam structures are developed in the free-to-use software “surface evolver” surface energy minimization program. These are “ideal” structures. Pressure drop and heat transfer are then investigated in each structure using the CFD module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out. The predictions showed that heat transfer characteristics are very close for low values of Reynolds number, but larger Reynolds numbers create larger differences between the results of the ideal and real structures. Conversely, the differences in pressure drop at any Reynolds number are nearly 100%. Results from the models are then validated by comparing them with experimental results taken from the literature. The validation suggests that the ideal structure poorly predicts the heat transfer and pressure drops.

Heat Transfer and Pressure Drop Simulation of CO2-Hydrate Mixture in Tube

2017 ◽  
Vol 25 (01) ◽  
pp. 1750005 ◽  
Author(s):  
Benedict Prah ◽  
Rin Yun
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Flow Characteristics ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Mixture Flow ◽  
Heat Transfer Coefficients ◽  
Two Phases ◽  
Energy Equations

The formation of CO2 hydrate during CO2 transportation presents a complex two-phase flow within tube. A two-dimensional CFD model for CO2 hydrate mixture flow in tube is derived based on the Eulerian multiphase flow modeling approach in which the two phases consist of CO2 gas and CO2 hydrate particles. A coupled Eulerian multiphase and nonisothermal flow model without phase-change is developed based on COMSOL Multiphysics built-in application modes. The model couples the mass, momentum, and energy equations for the two phases to solve the temperature and flow characteristics of the CO2 hydrate mixture flow in tube. CO2 hydrate particles are found to settle down during flow even under high velocity operation. The pressure drop increased linearly with inlet volume fraction from 1.29[Formula: see text]kPa for 0.1–5.2[Formula: see text]kPa for 0.5, and the related overall heat transfer coefficients of the CO2 hydrate mixture computed from the model ranged from 980 to 4000[Formula: see text]W/m2K with variation of CO2 hydrate volume fraction.

scholarly journals Heat Transfer Enhancement in Microchannel Flow: Presence of Microparticles in a Fluid

2010 ◽  
Author(s):  
Awad B. S. Alquaity ◽  
Salem A. Al-Dini ◽  
Evelyn N. Wang ◽  
Shahzada Z. Shuja ◽  
Bekir S. Yilbas ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Pressure Drop ◽  
Phase Change ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Microchannel Flow ◽  
Carrier Fluid ◽  
Volume Fractions ◽  
Energy Equations

In the present study, a numerical model was developed for laminar flow in a microchannel with a suspension of microsized phase change material (PCM) particles. In the model, the carrier fluid and the particles are simultaneously present, and the mass, momentum, and energy equations are solved for both the fluid and particles. The particles are injected into the fluid at the inlet at a temperature equal to the temperature of the carrier fluid. A constant heat flux is applied at the bottom wall. The temperature distribution and pressure drop in the microchannel flow were predicted for lauric acid microparticles in water with volume fractions ranging from 0 to 8%. The particles show heat transfer enhancements by decreasing the temperature distribution in the working fluid by 39% in a 1 mm long channel. Meanwhile, particle blockage in the flow passage was found to have a negligible effect on pressure drop in the range of volume fractions studied. This work is a first step towards providing insight into increasing heat transfer rates with phase change-based microparticles for applications in microchannel cooling and solar thermal systems.

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