Research Of Impinging Cooling Technology For Disk Laser Crystal

The thin disc laser allows the realization of lasers with high output power, highest efficiency and good beam quality, simultaneously. Yb:YAG is chosen as the preferred laser material because it primarily has a high quantum efficiency, guarantees good energy storage for pulsed operation, and exhibits a broad absorption line at 941nm for easy and effective pumping with InGaAs diodes. Yb:YAG being a quasi three level system is sensitive to temperature. If the temperature of disc laser crystal increased, disc laser's output threshold will increase, slope efficiency will reduce and output beam quality will turn worse. So, effective cooling system must be designed for disc laser crystal.This thesis firstly introduces the relevant principles of heat transfer and fluid dynamics. Then make a simple introduce of FLUENT and the experimental test platform. Before analyze the heat transfer character we demarcated the experimental test platform's heat flax.The heat transfer character of single jet module is studied by simulations and experiments in this thesis. Through analyze the heat transfer character at different impinging distances and different injection velocities, we can find that cooling system has bigger heat transfer capability when improve injection velocity and decrease impinging distance. Single jet module does not suitable for disc laser crystal cooling because of it can not improve injection velocity and injection area simultaneously.Jets array module's heat transfer character is analyzed. The peak values of heat transfer coefficient are nearly the same at different impinging distances. When the impinging distance is 5mm, the peak value of heat transfer coefficient is about 75000WK-1m-2. The maximum heat transfer coefficient will increas to 147000WK-1m-2 if the injection velocity is doubled. At the same pressure pipe jets array module can provide a lager injection velocity but smaller turbulivity than jets array module. The experiments and simulations results show that jets array module can achieve lager heat transfer coefficient than pipe jets array at the same boundary conditions.Overall, jets array module is suitable for disc laser crystal end-cooling.