SIMILARITY OF 2-FLUID FLOW HEATED BY A FUEL-ROD

General scaling laws for transient two-fluid flow heated by a rod are presented. The similarity of these processes can be ensured only by applying the same volume and time scale with identical model parameters. In practice, the requirement of similar interfacial friction terms cannot be fulfilled because of volume (diameter) reducing scale. Numerical examples show remarkable deviations between the state variables (the values of slip) of the prototype and those of the scaled model, especially with unsteady flow rates. The deviation becomes significant when the slip of phase velocities exceeds the range of 1.6 to 1.8. Volume and time scaling can be carried out only if the phase velocities are similar (slip equal to approximately 1 in the quasi-homogeneous flow model). Maintenance of the similarity of heat transfer processes of a heated fuel rod may necessitate time scaling. Furthermore, numerical examples are presented for a scale model of a prototype pressurized water reactor, employing the time-scaled homogeneous flow model.