Pore-Scale Numerical Investigation of Pressure Drop Behaviour Across Open-Cell Metal Foams

Abstract

The development and validation of a grid-based pore-scale numerical modelling methodology applied to five different commercial metal foam samples is described. The 3-D digital representation of the foam geometry was obtained by the use of X-ray microcomputer tomography scans, and macroscopic properties such as porosity, specific surface and pore size distribution are directly calculated from tomographic data. Pressure drop measurements were performed on all the samples under a wide range of flow velocities, with focus on the turbulent flow regime. Airflow pore-scale simulations were carried out solving the continuity and Navier-Stokes equations using a commercial finite volume code. The feasibility of using Reynolds-averaged Navier-Stokes models to account for the turbulence within the pore space was evaluated. Macroscopic transport quantities are calculated from the pore-scale simulations by averaging. Permeability and Forchheimer coefficient values are obtained from the pressure gradient data for both experiments and simulations and used for validation. Results have shown that viscous losses are practically negligible under the conditions investigated and pressure losses are dominated by inertial effects. Simulations performed on samples with varying thickness in the flow direction showed the pressure gradient to be affected by the sample thickness. However, as the thickness increased, the pressure gradient tended towards an asymptotic value.

Airflow measurement across negatively infiltration processed porous aluminum structures

“…Also, airflow measurement through a 12 mm thick Recemat RCM‐NCX 1723 sample shows reasonable agreement with numerically simulated (using x‐ray tomography images of the “real” structure) and measured values of unit pressure drop developed across the foam sample reported in Ref. . Though, flow length reported in Ref.…”

“…Though, flow length reported in Ref. was said to have a considerable influence on the flow performance due to the inhomogeneous topology (combination of irregular dodecahedron and tetrakaidecahedron cell with pentagonal faces described in Ref. ) of the sample geometry resulting in a nonuniform connectivity and variable length thereby necessitating a more developed flow field (increased computational time) to fully describe the entire flow behavior in a large sample especially at higher flow velocities.…”

Experimental Investigation on the Pressure Drop of Air Flows Through Aluminum and Nickel-Chromium Metallic Foams for HVAC Applications

“…They observed the decrease of the pressure gradient when the sample thickness was increased and the existence of an asymptotic value of the pressure gradient after a critical thickness was reached. Similar results were confirmed by Dukhan and Patel [5], Oun and Kennedy [6], and de Carvalho et al [7]. The goal of this experimental research was to test the performance of open-cell metal foams as a replacement of conventional aluminum fins adopted in air-water compact heat exchangers for HVAC emitters.…”

Inertial Sensitivity of Porous Microstructures

“…In many systems there may be transport processes with characteristic length scales much larger than the unit cell of the microstructure, as argued in, e.g. , Jin et al (2015), Agnaou et al (2016) andde Carvalho et al (2017). In such cases, one cannot reduce the REV to the unit cell of the porous medium and would need to determine an actual REV size for the flow process to be represented adequately.…”