Abstract
In piping system of a nuclear power plant, high-cycle thermal fatigue may occur due to stress amplitude in piping material of branch pipes induced by fluctuation of interface between hot water and cold water, which is called "thermal stratification layer". This study focuses on a position of the thermal stratification layer in a vertical branch pipe. Numerical simulation using transient Reynolds-averaged Navier-Stokes approach was carried out to clarify the relationship between main passage velocity and the thermal stratification layer position with varying the main passage velocity from 4 to 10 m/s. The simulation results showed that the thermal stratification layer positions corresponding each velocities were over predicted in the comparison with the experimental results of the past study. The discrepancies were between from 115 mm to 298 mm in the branch pipe with 43 mm diameter.
