ANALYSIS OF LIQUID FLOW-THROUGH CERAMIC POROUS-MEDIA USED FOR MOLTEN-METAL FILTRATION

A two-dimensional mathematical model has been developed to study fluid now inside ceramic foam filters, used for molten metal filtration, as a function of their structural characteristics. The model is based on the selection of a unit cell, geometric model, formed by two intercon nected half-pores. The good agreement between experimental and compute d permeabilities showed that the unit cell model approximates very wel l the effect of filter structure on the flow conditions inside the fil ter. The validity of the model is supported by the fact that permeabil ities are calculated from directly measured structural parameters, i.e ., without the introduction of any fitting variable, such as tortuosit y. The laminar flow solutions for the Navier-Stokes equation, in stead y state, were obtained numerically using the control-volume method. Th e boundary of the unit cell was represented through axisymmetrical, bo dy-fitted coordinates to obtain a better representation of the complex pore shape. The generality of the model, to study fluid flow in retic ulated media, was tested by comparing the computed specific permeabili ties with values measured for ceramic foam filters and for the new cer amic filter of lost packed bed (CEFILPB). Such a comparison shows good agreement and discloses a fundamental property of the last kind of po rous medium: the critical porosity. The model indicates how porosity a nd pore dimensions of reticulated filters may be tailored to meet spec ific fluid flow requirements.