Abstract
The conductive components of the pyro-breaker in the quench protection system (QPS) have high current density, a large number of electrical contacts and high thermal flux. The water system needs to meet the requirements of cooling and arc extinguishing at the same time. In a previous study, the bottleneck of the steady-state capacity appeared in the barrel conductor of the commutation section, which has a cylindrical cavity. The thermal stability of the commutation section at 100 kA level was simulated in ANSYS/Workbench. The results indicate a certain level of enhancement of the convective heat transfer coefficient of the cavity is required to reach the current capacity. However, the fluid flow inside the cavity is very complex, and the convective heat transfer coefficient is difficult to calculate. In this paper, Computational fluid dynamics (CFD) is applied to the optimization of the cooling water system of the pyro-breaker. By studying the enhancement method of convective heat transfer, optimization of the structure and processing method of the water channel are proposed. The convective heat transfer coefficients of the cylindrical cavity in these optimizations were calculated in CFX. A set of optimizations of the cavity, which can meet the requirements of China Fusion Engineering Test Reactor (CFETR), were obtained and verified by experiments.
Highlights
China Fusion Engineering Test Reactor (CFETR) has recently proposed several conceptual designs
The temperature difference between a surface roughness of R30 (76.64 ◦ C) and R100 is relatively smaller but has an obvious effect on the heat transfer enhancement. This indicates that the selected methods are feasible to enhance the convective heat transfer coefficient
The bottleneck of the steady-state capacity of the pyro-breaker appears at the barrel conductor in the commutation section
Summary
China Fusion Engineering Test Reactor (CFETR) has recently proposed several conceptual designs. As the pyro-breaker is connected in series in the main circuit, the current in the pyro-breaker will reach 100 kA in a steady state. Proper cooling can limit the size of the breaker and guarantee its safety in a steady state. Two methods are normally used to improve the heat exchange efficiency of a cooling water system. One is to increase the water flow rate, which normally leads to an increase of inlet water pressure [7,8]. This method may be limited by peripheral equipment and the sealing condition of the breaker. The other method is to enhance the convective heat transfer [9,10], which is more valuable when the general structure and flowrate of the cooling water system are determined
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