Heat Transfer and Fluid Dynamics in a Synthetic Impinging Jet over a Heated Surface

Project Team

Project Sponsor

Motivation

Synthetic jets are created by oscillatory pumping of fluid to and from an orifice. In its most common rendition, they have been fabricated using piezo-resistive actuators to produce periodic volume change in the cavity feeding the orifice, thereby periodically ingesting fluid and ejecting it as a jet, or a puff, into an open plenum. Although such a system has zero net flow from the orifice, it produces a jet with net momentum because the flow patterns are quite distinct in the ingestion compared to the ejection parts of the cycle. As such this jet can be used as a cooling device by configuring it to impinge onto the heated surface. Except for the earliest seminal work on the subject, most of the studies have been directed towards understanding synthetic jets created by pumps fashioned with piezo-resistive actuators as this type of device has shown promise as a small scale cooling technique for air-cooled electronic systems..

Fig.1: Schematic of the synthetic jet generation during its 3 stages: (a) initial state, (b) forward stroke (ejection of fluid), and (c) backward stroke (injection of fluid)

Project Description

In the majority of the previous work on the subject, the synthetic jet was created using an oscillating diaphragm, where the diaphragm is actuated using piezo-resistive devices (Fig. 1). The objective of the present work is to de-couple the behavior of the synthetic jet from the manner in which it is created. If successful, the resulting problem will allow the investigation of fundamental behavior that is not influenced by the design of the device. The evolution of the velocity and temperature fields throughout the process, the effect of the Reynolds number Re, jet-to-surface distance H, and the driving frequency f on the heat transfer are studied. Also, the possibility of geometrically scaling the problem to larger dimensions is being examined. [more]

Publications

Silva, L. and Ortega A.,     "Convective Heat Transfer Due to an Impinging Synthetic Jet: A Numerical Investigation of a Canonical Geometry," ITherm, Las Vegas, Nevada, USA (2010)
PDF (1564 K)

Silva, L. and Ortega A.,     "Numerical Simulation of Local Heat Transfer and Scaling of a Synthetic Impinging Jet in a Canonical Geometry," IMECE, Vancouver, British Columbia, Canada (2010)
PDF (353 MB)