Study on Thermal Stratification by Cavity Flow in a Branch Pipe with a Closed End (Concept of L1 Evaluation Method).

Abstract

In a branch pipe with a closed end, the cavity flow penetrates into the branch pipe from the main loop and the thermal boundary layer occurs because the cavity flow is a hot fluid, but the heat removal causes the colder fluid in the branch pipe. It is possible for the thermal stratification to affect the structural integrity. Therefore, it is necessary to establish the pipe design standard to suppress thermal fatigue. The pipe design standard consists of the maximum penetration length (L1) and the minimum penetration length (L2). First of all, in order to establish the evaluation method for Li, the visualization tests and the high temperature and pressure test were carried out. The method reproduces the penetration length by cavity flow in several types of the vertical branch pipes within 10% accuracy.