Practical CFD Modeling of Synthetic Air Jets for Thermal Management of Electronics

This paper discusses experimental and theoretical results for several embodiments of pulsed air jet technology. Pulsed air jets, also called synthetic jets, require an implementation strategy that is quite different from steady-flow devices such as fans and blowers. Simply replacing a fan with a synthetic jet will most likely result in a failure to cool a device as intended. The principal goal of this paper is to determine whether a commercially available CFD code can be used as a design tool for the optimization of synthetic jet systems. To this end, a general purpose CFD code was used to estimate the flow spreading, volume of entrainment, and heat transfer characteristics of a synthetic air jet. Commercially available CFD software, FloEFD, was used to make these determinations. The methods explained are relevant primarily to this CFD software, but are also germane to a number of other codes. Because synthetic jets are a transient phenomenon, a change in the specific heat of the model materials is applied in order to increase the speed of the thermal solution. A detailed analysis of the complete actuator assembly is unnecessary if the velocity/time or pressure/time waveform at the air jet port is used as an input parameter. Three experiments were performed to validate the CFD models, 1. flow divergence, 2. volumetric entrainment, and 3. heat transfer.