scholarly journals Review and a Theoretical Approach on Pressure Drop Correlations of Flow through Open-Cell Metal Foam

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3153
Author(s):  
Huizhu Yang ◽  
Yongyao Li ◽  
Binjian Ma ◽  
Yonggang Zhu
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Metal Foams ◽  
High Porosity ◽  
Open Cell ◽  
Wide Range ◽  
Flow Through

Due to their high porosity, high stiffness, light weight, large surface area-to-volume ratio, and excellent thermal properties, open-cell metal foams have been applied in a wide range of sectors and industries, including the energy, transportation, aviation, biomedical, and defense industries. Understanding the flow characteristics and pressure drop of the fluid flow in open-cell metal foams is critical for applying such materials in these scenarios. However, the state-of-the-art pressure drop correlations for open-cell foams show large deviations from experimental data. In this paper, the fundamental governing equations of fluid flow through open-cell metal foams and the determination of different foam geometry structures are first presented. A variety of published models for predicting the pressure drop through open-cell metal foams are then summarized and validated against experimental data. Finally, two empirical correlations of permeability are developed and recommended based on the model of Calmidi. Moreover, Calmidi’s model is proposed to calculate the Forchheimer coefficient. These three equations together allow calculating the pressure drop through open-cell metal foam as a function of porosity and pore diameter (or strut diameter) in a wide range of porosities ε = 85.7–97.8% and pore densities of 10–100 PPI. The findings of this study greatly advance our understanding of the flow characteristics through open-cell metal foam and provide important guidance for the design of open-cell metal foam materials for different engineering applications.

Pore-Level Numerical Simulation of Open-Cell Metal Foams With Application to Aero Engine Separators

2014 ◽  
Author(s):  
Thiago Piazera de Carvalho ◽  
Hervé P. Morvan ◽  
David Hargreaves
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Porous Medium ◽  
Pressure Drop ◽  
Metal Foam ◽  
Metal Foams ◽  
Open Cell ◽  
X Ray ◽  
Pore Level ◽  
Aero Engines

In aero engines, the oil and air interaction within bearing chambers creates a complex two-phase flow. Since most aero engines use a close-loop oil system and releasing oil out is not acceptable, oil-air separation is essential. The oil originates from the engine transmission, the majority of which is scavenged out from the oil pump. The remainder exits via the air vents, where it goes to an air oil separator called a breather. In metal-foam-style breathers separation occurs by two physical processes. Firstly the largest droplets are centrifuged against the separator walls. Secondly, smaller droplets, which tend to follow the main air path, pass through the metal foam where they ideally should impact and coalesce on the material filaments and drift radially outwards, by the action of centrifugal forces. Although these devices have high separation efficiency, it is important to understand how these systems work to continue to improve separation and droplet capture. One approach to evaluate separation effectiveness is by means of Computational Fluid Dynamics. Numerical studies on breathers are quite scarce and have always employed simplified porous media approaches where a momentum sink is added into the momentum equations in order to account for the viscous and/or inertial losses due to the porous zone [1]. Furthermore, there have been no attempts that the authors know of to model the oil flow inside the porous medium of such devices. Normally, breathers employ a high porosity open-cell metal foam as the porous medium. The aim of this study is to perform a pore-level numerical simulation on a representative elementary volume (REV) of the metal foam with the purpose of determining its transport properties. The pore scale topology is represented firstly by an idealized geometry, namely the Weaire-Phelan cell [2]. The pressure drop and permeability are determined by the solution of the Navier-Stokes equations. Additionally, structural properties such as porosity, specific surface area and pore diameter are calculated. The same procedure is then applied to a 3D digital representation of a metallic foam sample generated by X-ray tomography scans [3]. Both geometries are compared against each other and experimental data for validation. Preliminary simulations with the X-ray scanned model have tended to under predict the pressure drop when compared to in-house experimental data. Additionally, the few existing studies on flow in metal foams have tended to consider laminar flow; this is not the case here and this also raises the question that Reynolds-averaged turbulence models might not be well suited to flows at such small scales, which this paper considers.

3D NUMERICAL INVESTIGATION OF FLUID FLOW THROUGH OPEN-CELL METAL FOAMS USING MICRO-TOMOGRAPHY IMAGES

2014 ◽  
Vol 17 (11) ◽  
pp. 1019-1029 ◽  
Author(s):  
Mohammad Zafari ◽  
Masoud Panjepour ◽  
Mohsen Davazdah Emami ◽  
Mahmood Meratian
Keyword(s):  
Fluid Flow ◽  
Numerical Investigation ◽  
Metal Foams ◽  
Open Cell ◽  
Flow Through ◽  
Micro Tomography

An Effect of Fractal Flow Conditioner Thickness on Turbulent Swirling Flow

2013 ◽  
Vol 315 ◽  
pp. 93-97 ◽  
Author(s):  
Bukhari Manshoor ◽  
N.F. Rosidee ◽  
Amir Khalid
Keyword(s):  
Fluid Flow ◽  
Steady State ◽  
Pressure Drop ◽  
Swirling Flow ◽  
Plate Thickness ◽  
Flow Characteristics ◽  
Space Filling ◽  
Flow Through ◽  
Experimental Fluid ◽  
Good Agreement

Fractal flow conditioner is a flow conditioner with a fractal pattern and used to eliminate turbulence originating from pipe fittings in experimental fluid flow applications. In this paper, steady state, incompressible, swirling turbulent flow through circle grid space filling fractal plate (Fractal flow conditioner) has been studied. The solution and the analysis were carried out using finite volume CFD solver FLUENT 6.2. The turbulence model used in this investigation is the standardk-εmodel and the results were compared with the pressure drop correlation of BS EN ISO 5167-2:2003. The results showed that the standardk-εmodel gave a good agreement with the ISO pressure drop correlation. Therefore, the model was used further to predict the effects of circle grids space filling plate thickness on the flow characteristics.

Parallel Flow in Ordered Fibrous Structures: An Analytical Approach

2009 ◽  
Author(s):  
A. Tamayol ◽  
M. Bahrami
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Entire Range ◽  
Analytical Approach ◽  
The Other ◽  
High Porosity ◽  
Fibrous Media ◽  
Fully Developed Flow ◽  
Wide Range ◽  
Hexagonal Arrays

In this study, fully-developed flow parallel to ordered fibrous structures is investigated analytically. The considered fibrous media are made up of inline (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered patterns over the entire range of porosity and the results are compared with the proposed solutions. The developed models are successfully verified through comparison with existing experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometry; on the other hand, for lower porosities the hexagonal arrays results in lower pressure drop, as expected.

Developing an Application for Refractory Open Cell Metal Foams in Jet Engines

2004 ◽  
Vol 851 ◽  
Author(s):  
Wassim E. Azzi ◽  
William L. Roberts ◽  
Afsaneh Rabiei
Keyword(s):  
Pressure Drop ◽  
Gas Turbines ◽  
High Speed ◽  
Infrared Imaging ◽  
Metal Foam ◽  
Turbine Blades ◽  
Metal Foams ◽  
Thermodynamic Efficiency ◽  
Open Cell ◽  
The Difference

ABSTRACTThe thermodynamic efficiency of the Brayton cycle, upon which all gas turbines (aeropropulsion and power generation) are based on scales with the peak operating temperature. However, the peak temperature is limited by the turbine blades and the temperature they can withstand. The highest temperatures in the gas turbine occur in the combustor region but these temperatures are often too high for turbine blades. As a result, the combustion products must be diluted with relatively cooler air from the compressor to reduce the temperature to tolerable levels for the turbine blades. This research suggests placing a ring of high temperature open cell metal foam between the combustors and turbine sections of the jet engine to mix and average the difference in temperatures resulting from the cooling schemes in combustor cans. Temperature mixing effect was tested using a special setup with the application of an infrared camera and streams of hot and cold air passing through the foam. High speed flow pressure drop around Mach 1 (340 m/s) was done on the same foam samples to understand pressure drop in the compressible regime of air. Infrared imaging showed that open cell metal foams successfully mixed and averaged the difference in temperatures of the hot and cold gasses thus creating a more uniform temperature profile while pressure drop testing revealed that open cell metal foams result in minimal pressure drop at high flows especially when the increase in temperature in taken into consideration.

Geometric Mean of Fin Efficiency and Effectiveness: A Parameter to Determine Optimum Length of Open-Cell Metal Foam Used as Extended Heat Transfer Surface

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Tisha Dixit ◽  
Indranil Ghosh
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Geometric Mean ◽  
Fluid Velocity ◽  
High Surface ◽  
Metal Foams ◽  
Heat Sinks ◽  
High Porosity ◽  
Open Cell ◽  
Fin Efficiency

High porosity open-cell metal foams have captured the interest of thermal industry due to their high surface area density, low weight, and ability to create tortuous mixing of fluid. In this work, application of metal foams as heat sinks has been explored. The foam has been represented as a simple cubic structure and heat transfer from a heated base has been treated analogous to that of solid fins. Based on this model, three performance parameters namely, foam efficiency, overall foam efficiency, and foam effectiveness have been evaluated for metal foam heat sinks. Parametric studies with varying foam length, porosity, pore density, material, and fluid velocity have been conducted. It has been observed that geometric mean of foam efficiency and foam effectiveness can be a useful parameter to exactly determine the optimum foam length. Additionally, the variation in temperature profile of different foams heated from one end has been determined experimentally by cooling these with atmospheric air. The experimental results have been presented for open-cell metal foams (10 and 30 PPI) made of copper/aluminium/Fe–Ni–Cr alloy with porosity in the range of 0.908–0.964.

Fluid Flow Characteristics for Partially-Confined Compact Plain-Plate-Fin Heat Sinks

2005 ◽  
Author(s):  
M. P. Wang ◽  
T. Y. Wu ◽  
J. T. Horng ◽  
C. Y. Lee ◽  
Y. H. Hung
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Sink ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Heat Sinks ◽  
Experimental Investigations ◽  
Channel Height ◽  
Fluid Flow Characteristics

A series of experimental investigations with a stringent measurement method on the study of the fluid flow behavior for confined compact heat sinks in forced convection have been successfully conducted. In the present study, a theoretical model to effectively predict the velocity and pressure drop for partially-confined heat sinks has been successfully developed. The air velocities flowing into heat sink Us through side bypass U1 and top bypass U2 for various 0.47<H/Hc<1 ratios are evaluated, where H/Hc is the ratio of the heat sink height to channel height. The maximum and average deviations of the velocities predicted by the present model from the experimental data are less than 20.31% and 13.13%, respectively, for confined compact heat sinks. Besides, the results show a good agreement between the predicted results and the experimental data of the pressure drop for the cases of H/Hc = 1. Nevertheless, the relative deviation of the predictions from the experimental data becomes more significant with decreasing H/Hc ratio, i.e., increasing the top bypass of confined compact heat sink. A new modified correlation of pressure drop including the H/Hc effect is presented. The maximum and average deviations of the results predicted by the new correlation from the experimental data are 14.48% and 7.72%, respectively.

Experimental and Tomography-Based CFD Investigations of the Flow in Open Cell Metal Foams With Application to Aero Engine Separators

2015 ◽  
Author(s):  
Thiago P. de Carvalho ◽  
Hervé P. Morvan ◽  
David Hargreaves ◽  
Hatem Oun ◽  
Andrew Kennedy
Keyword(s):  
Experimental Data ◽  
Particle Tracking ◽  
Metal Foams ◽  
Air Separation ◽  
Minimum Size ◽  
Separation Mechanism ◽  
Pore Scale ◽  
Open Cell ◽  
Wide Range ◽  
Aero Engine

Oil-air separation is a key function in aero engines with closed-loop oil systems. Typically, aero engine air/oil separators employ the use of a porous medium such as open cell metal foams, as a secondary separation mechanism. Assessing its impact on overall separation is important since non-captured oil is released overboard. Computational fluid dynamics offers a possibility to evaluate the metal foam separation effectiveness. A pore scale numerical modelling methodology is applied to determine the transport properties of fluid flow through open cell metal foams. Microcomputer tomography scans were used to generate a 3D digital representation of commercial open cell metal foams of different grades. Foam structural properties such as porosity, specific surface, pore size distribution and the minimum size of a representative elementary volume are directly extracted from the CT scans. Subsequently, conventional finite volume simulations are carried out on the realistic tomography-based foam samples. Simulations were performed for a wide range of Reynolds numbers. The feasibility of using standard Reynolds-averaged Navier-Stokes (RANS) turbulence models is investigated here. As part of the method validation, samples with varying lengths were simulated. Pressure drop values were compared on a length-normalized basis against in-house experimental data. The oil phase was modelled using a Lagrangian particle tracking approach. Boundary conditions for the oil phase were extracted from a previous CFD simulation of a full breather device in the ground idle regime (worst separation effectiveness). Steady state particle tracking simulations were run for droplet diameters ranging from 0.5–15 μm, and for flow inlet velocities ranging from 10–60 m/s. Stochastic tracking was taken into account in order to model the effects of turbulence on the particle trajectories. Simulations were run on different types of foam and the results are compared qualitatively. The procedure has shown that pore scale modelling is a valid tool to capture the flow field and model oil separation inside open cell metal foams. However, at the moment there is no experimental data available for validation of the oil phase modelling.

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