Scaling Criteria for Two-Phase Flow Loops and Their Application to Conceptual 2×4 Simulation Loop Design

Scaling criteria for a natural circulation loop under single- and two-phase flow conditions are derived from the fluid balance equations, boundary conditions, and solid energy equations. For a single-phase flow case, the continuity, integral momentum, and energy equations in one-dimensional area-averaged forms were used. For a two-phase flow case, the one-dimensional drift-flux model obtained from the short time temporal averaging and the sectional area averaging was used. The scaling criteria are applied to a conceptual design of a 2 x 4 loop facility for simulating the Babcock & Wilcox Company 177 NSSS lowered loop plant design. Numerical calculations performed to meet the similarity requirement indicated that the most severe condition in terms of the thermohydraulic simulation is imposed by the friction number requirement over the hot leg section. Therefore, a solution for the similarity criteria based on the hot leg was presented. For three separate circumstances, it was shown that a solution in the form of the length ratio as a function of the area ratio is feasible in each case.