DYNAMIC MODEL OF RAPID COOLANT FILTRATION THROUGH A BED OF MICRO FUEL PARTICLES

It is shown that mathematical hydrodynamic models of micro fuel beds can’t describe viscous and inertial effects truly. The filtration equations obtained by averaging the equation of viscous fluid motion over an elementary volume and containing the so-called viscous term are valid only for the infinite porous medium. Using these equations and no-slip condition on the impermeable ends of bed leads to discrepancy between estimated and observed data. The constructed rapid coolant filtration model is based on the ideal fluid motion laws with a volume interphase interaction force, which is represented as a divergence of a tensor with potential and vortex components. In this case, the potential component reflects the contribution of the resistance forces to the normal pressure of the coolant and is a “hidden” parameter – the reason for experimental data spread. Using the model, dynamics of the coolant flow at the inlet and outlet of the fuel bed is investigated and the matching conditions for velocity and pressure vector are determined. These conditions make it possible to relate the filtration equation and viscous fluid motion equation on the bed permeable boundaries. Due to dominance of inertia forces at entrance and exit of the bed, the stream is refracted: at the inlet towards the normal to the bed boundary, and at the exit towards the tangent. Accounting for this effect the optimize fuel bed contours in terms of thermal physics and neutron physics will be obtained.

mathematical model, fuel bed, micro fuel particles, filtration, interface interaction tensor, matching conditions, Bernoulli’s function breaking, inertial and viscous effects

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