流体直接冷却Nd: YAG片状激光器系统中,流体流经增益介质时存在水力入口段,使用Ansys仿真软件,讨论了不同水力入口段距离对流体热交换系数的影响,并在此基础上,将水力入口段距离进行分类,分析了水力入口段距离对热应力以及光束传输的影响; 模拟了不同冷却液的冷却效果; 研究了流体处于不同流动状态时,水力入口段距离与流体热交换系数的关系,以及水力入口段距离与增益介质温度分布的关系; 得到了这种高功率激光器冷却系统中,最佳水力入口段距离的范围。结果表明：流体流经增益介质时,不同的水力入口段距离只是规律性地移动了流体的热交换系数曲线,因此,避开流体热交换系数曲线中变化较大的区域,即0～2.25 mm范围内的水力入口段距离,可实现介质内更小的温度梯度,同时降低热应力以及波前畸变,从而实现更好的冷却效果。

In the Nd: YAG thin disk laser system, there is a hydraulic entrance distance when the fluid flows through the gain medium. By using the Ansys simulation software, the influence of the different hydraulic entrance distances on the heat transfer coefficient of the fluid was discussed. The influence of the hydraulic entrance distance on the thermal stress and the beam transmission was analyzed. The cooling effect of different coolant is simulated. When the fluid was in different flow state, the relationship between the hydraulic entrance distance and the heat transfer coefficient of the fluid was studied, while the relationship between the hydraulic entrance distance and the temperature of the medium was also studied. The range of the optimal hydraulic entrance distance was obtained in the high power laser cooling system. The results show that when the fluid flows through the gain medium, the different hydraulic entrance distance only moves the heat transfer coefficient curve of the fluid regularly. Therefore, it can realize small temperature gradient in the medium, while reducing the thermal stress as well as the wavefront distortion by avoiding the distance region (0-2.25 mm) where the heat transfer coefficient curve changes greatly, and finally, achieve a better cooling effect.