**3. Results and Discussion**

This study focused on the characteristics of the device of PAJs with respect to their capacity for heat dissipation when used with a HI-LED. The linear jet path may provide a greater amount of wind, but the wind speed was low. While the linear jet path can effectively reduce the thermal resistance of thermal diffusion, for LED lights more than 3 W, the cooling effect is poor. When the device of the piezo actuation jet is too close to the heat source, the high temperature surrounding the heat source will be returned, causing the chamber temperature to rise and reducing the cooling effect. The flared jet path has a narrower outlet area to enhance the wind speed of the jet stream and can significantly reduce the thermal resistance of thermal convection. Moreover, the flared design on both sides of the jet path can increase the cooling area and slightly reduce the diffusion resistance. We altered the structural designs of the devices, as well as their operating conditions and placement in order to investigate the impacts of such changes on the cooling effect. We chose the optimal design and input conditions and then determined how to improve the performance of a device of piezo actuation jet. The size of the piezoelectric sheet will directly influence the performance of the device of the piezo actuation jet. In the present study, we used 41 mm and 31 mm piezoelectric sheets to conduct experiments under the same conditions. The area of the device of the piezo actuation jet was only 4% of the current commercial rotary fan.
