Swirl tube design and analysis of the magnetic pole shield for long pulse operation of EAST NBI system based on subcooled boiling

摘要

The Neutral Beam Injection (NBI) auxiliary heating system for Experimental Advanced Superconducting Tokamak (EAST) is designed with 180 degrees magnetic field deflection to deflect the particles that are not neutralized during the beam transmission. For protecting the deflection magnet from the influence of the divergent beam, the pole shields are designed to be placed on both sides of its optical path, and the highest power density of the above deposit will be as high as several MW/m(2). In order to ensure reliable operation of 100s and even 1000s long pulse EAST-NBI system, it is very important to enhance the heat transfer performance of these shields. A novel heat transfer enhancement design of pole shield with swirl tube for EAST-NBI system is presented in this paper. By using a verified subcooled boiling model, the performance optimization of the key structural parameters is completed according to the operation limit of the magnetic pole shield and the cooling water system, and also the final structural optimization scheme is checked. The results show that heat transfer performance of the proposed scheme can well satisfy the requirements of the long pulse design. This study provides a potential method for the heat transfer enhancement design of other high heat flux components in EAST-NBI system, which is of great theoretical and practical significance for the future operation with long pulse (over 1000 s) and high power 2(similar to)4 MW.