Study on heat transfer enhancement of fin-and-tube heat exchangers in fast-axial-flow CO₂ lasers

In order to solve the problem of high pressure loss and low heat transfer efficiency of fin-and-tube heat exchangers in a high power axial flow fast CO₂ laser in the thick plate cutting field, computational fluid dynamics software ANSYS was used to analyze the heat transfer characteristics of 3 kinds of vortex generators. The shape, length, height and angle of trapezoidal winglet vortex generator with better heat transfer performance were optimized. The reliability of the numerical simulation data was verified through an open loop wind tunnel experimental platform. The results show that the optimum heat transfer performance is gotten with trapezoidal winglet vortex generator of 11mm length, 2.6mm height and 30° angle of attack which is gradually reduced. Compared with the generator without installing vortex, the heat transfer performance of trapezoidal winglet vortex generator Nu is increased by 8%~22%, and the friction factor is increased by 16%~27%, in Reynolds number of 600~1600. Test results of CP4000 series axial fast flow CO₂ laser show that the stable output power of 8h is 4216W, 5.4% higher than the rated output power. The study improves the plate cutting capacity of CP4000 series lasers.