Characterization of the thermal performance of multi piezoelectric fans for cooling a semi-cylindrical concave surface

Abstract

Piezoelectric fan is widely used in the heat removal of high-temperature devices for its advantages of simple structure, low energy consumption, low noise, and good wind orientation. A theoretical and numerical study of characterizing the flow and heat transfer performances induced by single and multi-vibrating piezoelectric fans for cooling heated semi-cylindrical concave surface is conducted in this work. Two kinds of numerical models based on a dynamic meshing scheme and a user defined function describing the time-varying displacement of vibrating fans are employed to capture the instantaneous vortex structures and temperature contours on the semi-cylindrical concave surface. The influence mechanisms on heat removal performance of some vital factors, such as the dimensionless fan-to-fan pitch (P/W), vibrating phase difference and the dimensionless fan tip-to-concave surface distance (G/A) are analysed. The results prove that the evolution of the transient vortical structures around a single vibrating piezoelectric fan for cooling concave surface is almost the same as the case for cooling plane surface. The interaction of the streaming flow induced by multi fans is mainly concentrated in the clearance area between adjacent fans rather than the vibration envelopes. Moreover, the in-phase vibrating condition is more sensitive to the change of P/W and G/A than that of the out-of-phase. The simulations furnish a good reference for the design and optimization of multi piezoelectric fans.