Numerical Investigation on Characteristics of Fully Developed Nucleate Boiling (Fdb) in Petal-Shape Fuel Assembly Channel

Abstract

FDB distinguishes between single-phase flow and two-phase flow. In this paper, the flow boiling in a 3×3 petal-shaped fuel assembly channel and the characteristics of FDB were numerical investigated. If the diameter of bubble exceed the departing bubble diameter, the bubble can depart from the wall, FDB is determined. The results showed that the heating power had a minor effect on FDB. As the inlet subcooling increased, the temperature of mainstream on the cross section of FDB decreased and wall superheat increased. As the inlet mass flow rate increased, the mainstream temperature on the section of FDB increased and the wall superheat increased. With the pressure increase, the change trend of mainstream temperature and wall superheat were the same as mass flow rate increased. A factor was introduced to modify Unal’s expression. Comparing with simulation result, the error of modified expression was less than 15%.

Keywords: Petal-shape fuel rod, subcooled boiling, fully developed boiling, numerical simulation