Thermodynamic analysis and heat transfer optimization of the CRAFT NNBI calorimeter

Abstract

ABSTRACT In the process of neutral beam injection (NBI), the high-energy neutral beams, which are up to 31 MW/m2 and last for 3600 s in some cases, impinge on the calorimeter, which is a high-heat-flux component. Therefore, it is necessary to study the heat transfer performance of the calorimeter to ensure the testing and commissioning of NBI systems. First, the uniformity of the water mass flow distribution in each branch pipe of the calorimeter under five different flow configurations was studied. The results show that when two adjacent branches form a group of circuits, the uniformity of the mass flow distribution and the heat transfer capacity are better. Second, the influence of bending the middle of the pipe into several different buffer support structures on the deformation of the branch pipe was studied. Third, the heat transfer performance was compared between the optimized structure and the original circular pipe. Under the same water mass flow conditions, the maximum deformation of the optimized structure is reduced to 2.79 mm, and the maximum temperature is reduced by 30.31%, indicating effective improvement in the heat transfer performance and a reduction in deformation. Therefore, the optimized calorimeter can adapt to the future operational environment under a higher heat flux and long pulse. Finally, several groups of branch pipes were assessed to verify the feasibility of the design. This research can also provide theoretical and engineering support for the future design of calorimeters and other components under long-pulse and high-heat-flux operation.