Optimization design of water-cooled mirror for low thermal deformation

A novel structure of mirror layer for water-cooled mirror is proposed in this paper. Numerical simulations are carried out to compare the performance between the novel and conventional structure by examining four types of flow passage configuration and inlet/outlet arrangement. The analyses are based on computations of fluid-solid conjugated heat transfer. Advantages and limitations of each design are evaluated by analyzing the temperature rise, temperature uniformity, thermal deformation and deformation uniformity of the mirror surface. It is concluded that the novel structure of mirror layer shows steady improvement in both magnitude and uniformity of the thermal deformation. An effective design for water-cooled mirror must provide effective heat dissipation and ensure enough stiffness for the mirror layer at the same time. The configuration locating bent channels in the center and keeping the inlet/outlet away from the center is beneficial to water-cooled mirror, as it enhances heat dissipation and ensures stiffness. The average Reynolds number around 1000 is figured out to be optimal hydraulic conditions for different designs of water-cooled mirrors.