Experimental Determination of Permeability and Inertia Coefficients of Mechanically Compressed Aluminum Porous Matrices

A heat exchanger, using mechanically compressed microporous matrices, is being developed for cooling high power electronics. The thermal efficiency of this new device depends on the hydraulic characteristics (porosity φ, permeability K, and Forchheimer coefficient c_F) of the matrix inserted in it. These quantities have to be obtained experimentally as predictive models do not exist. Twenty-eight compressed matrices are initially chosen for experimental testing. Based on structural requirements, nine matrices are selected for full hydraulic characterization. The determination of permeability and inertia coefficient of each matrix is performed following a proposed direct methodology based on the curve fitting of the experimental results. This methodology is found to yield more consistent and accurate results than existing methods. The uncertainty of the experimental results is evaluated with a new and general procedure that can be applied to any curve fitting technique. Results indicate that the tested matrices have a unique characteristic, that of a relatively wide porosity range, from 0.3 to 0.7, within a relatively narrow permeability range, from 1.0 × 10⁻¹⁰ m² to 12 × 10⁻¹⁰ m². The inertia coefficient varies from 0.3 to 0.9. These hydraulic characteristics lead to a microporous heat exchanger performing within requirements.