Flow characteristic of a valveless piezoelectric micropump applying Coanda effect

A valveless piezoelectric micropump based on Coanda effect was presented. The effects of the angle and the length of the diffuser as well as the Reynolds number on the performance of the micropump were studied. The numerical simulation was done to obtain the flow field as well as the flow rate and the volumetric efficiency of the micropump. The range of the diffuser angle was from 15°to 60°, and Reynolds numbers was from 200 to 800. It shows that as the diffuser angle increased, the maximum flow rate rose from 15° to 45°, and then dropped sharply after 45°. When the Reynolds number was low, the fluid was discharged through both the inlet and outlet pipes in the pumping process. With the increasing of the Reynolds numbers, more fluid was discharged through the outlet pipe than the other one. When the Reynolds number was as high as 800, the fluid in the chamber was sprayed out only through the outlet pipe and also some fluid was entrained through the inlet pipe and sprayed out through the outlet. Thus, the volumetric efficiency of the micropump could reach over 50%. The maximum net flow rate 0.767 ml/min and volumetric efficiency 50.22% are obtained at the angle 45°, length of the diffuser 362 μm and Re = 800.