Permeability Measurement and Numerical Modeling for Refractory Porous Materials

The transport properties of the ceramic based refractory coating to allow proper permeation of degradation products during the pyrolysis of expanded polystyrene (EPS) foam in Lost Foam Casting (LFC) have an important influence on the success of the casting process. This paper proposes a new apparatus to evaluate the permeability of the refractory coatings in a relatively large differential pressure range that is expected during the casting process. A number of commercial coatings currently used in major LFC foundries are evaluated, and the results show significant differences in their transport properties. The proposed interpretation method of measured gas flow data is considered the slippage and inertia effects that occur in measuring gas permeability. It is found that special care should be taken to measure the coating permeability in a large velocity range. Comparisons of test results from this new device are made to the widely used General Motors (GM-hereafter referenced as Foundry A) Perm-meter. The proposed measurement technique is more reliable to evaluate the permeability of the refractory LFC coatings in a large velocity range and considers inertia effects. A procedure using three-dimensional computational fluid dynamics code (FLOW3D) is developed to simulate experimental gas flow data for solving complex boundary value problems that use these coatings.