Synthetic jet with piezoelectric flaps mechanism for enhancement of heat transfer performance and energy harvesting

Abstract

The conventional synthetic jet's inferior thermal performance limits its applicability in confined space thermal management. The present study proposes a novel design incorporating external mechanisms that contain stainless steel flaps over which piezoelectric discs are pasted. These vibrate through flow motion piezoelectric flaps opposite each other in addition to the acoustically actuated synthetic jet. Placing piezoelectric (PZT) material on stainless steel flaps allows energy harvesting from the impinging synthetic jet's flow-induced vibrations. The synthetic jet operates at a frequency of 31 Hz and amplitude of 10 V, corresponding to a Reynolds number of 13000 and a stroke length of 16.2. The effect on the heat transfer characteristics is analyzed for placement of the flaps at different locations along and away from the jet centreline. Results reveal up to a 46% enhancement in the area-averaged Nusselt number. Optimal heat transfer conditions are observed at lower orifice-to-surface (z/d) and flap-to-surface (s/d) values. This enhancement is attributed to improved mixing between the flaps and the heated surface, boosting convective heat transfer and reducing recirculated heated air toward the orifice. Notably, higher heat transfer enhancements are observed when s/d values are lower (<2). Moreover, piezoelectric flaps enable energy harvesting from flow-induced vibrations, with a maximum power conversion of 195 mW per flap, equivalent to 2.20 % of the power supplied to actuate the synthetic jet. Therefore, the proposed synthetic jet design improves thermal performance and conserves energy induced by the synthetic jet, making it an effective thermal management technique. Keywords: Synthetic jet, thermal management, piezoelectric, PZT, energy harvesting