Numerical analysis of the subcooled boiling phenomena in a wire-wrapped annulus

Abstract

The wire-wrapped tight lattice fuel assembly is one of the options for small modular reactors. To investigate the performance of this assembly, the subcooled boiling characteristics in a wire-wrapped annular have been analyzed in the present work. The Eulerian two-fluid model coupled with the RPI wall boiling model was employed in the simulation. The mathematical models are validated by the subcooled boiling experimental data of the circular channel first, and then the simulation for wire-wrapped annular is carried out. The distributions of fluid temperature, wall temperature, vapor volume fraction, and heat flux partitions under a typical pressurized water reactor condition are gained. In the simulation conditions of the current wire-wrapped annular, the results indicate the non-uniform circumferential heat transfer can be ignored in subcooled boiling conditions, and the maximum vapor volume fraction occurred near the wire surface region. In addition, the increase of wire pitch increases the swirl intensity, at the same time, it also will increase the maximum vapor volume fraction near the rod surface region, which may cause DNB to occur earlier. Therefore, the wire pitch should be chosen carefully when the wire-wrapped assembly is applied to the pressurized water reactors. This work can provide a reference for the design of wire-wrapped tight lattice assembly applied in small modular reactors.