Thermal analysis of piezoelectric actuators for active cooling of RF phased array radars
RF communications and radar systems present an extreme thermal management challenge. These systems are comprised of tightly packaged high wattage components requiring a controlled temperature to meet performance and reliability parameters. One approach being pursued to meet this thermal challenge is embedding piezoelectric actuators within the electronics to create synthetic air jet drives for localized cooling. U.S. Army AMRDEC is developing and testing actuator test beds to mature the concepts and develop practical solutions. This investigation attempts to model these actuators in a CFD thermal analysis program, verify the results of the models with the current test beds, and then insert the model in conceptual designs of phased array antennas. The goal of the investigation is to gain insight into the practical application of a maturing thermal management concept in a real world application. These cooling devices have achieved over 2.5 W/cm2 cooling capacity in a 1.3 cm3 package.
Local Convective Heat Transfer From a Constant Heat Flux Flat Plate Cooled by Synthetic Air Jets
The effects of a small-scale, rectangular synthetic air jet on the local convective heat transfer from a flat, heated surface were measured experimentally. The synthetic jet impinges normal to the surface and induces small-scale motions by zero-net mass flux, time-periodic entrainment, and ejection of ambient air at frequencies whose periods are far higher than the characteristic thermal time scale. The velocity field between the jet orifice and the target plate is measured in planar cross sections using particle image velocimetry and is related to the local heat transfer from the plate. The present work suggests that synthetic jets can lead to substantial enhancement of the local heat transfer from heated surfaces by strong mixing that disrupts the surface thermal boundary layer. The dependence of the local heat transfer coefficient on the primary parameters of jet motion is characterized over a range of operating conditions.
A MEMS Active Cooling Substrate for Microelectronics Thermal Management
Thermal management of electronic systems is of increasing concern as densities and power consumption increase. Typical thermal management solutions are modular in nature; e.g., a heat sink and/or fan area added to a heat-producing part. In this work, an integrated solution, the active cooling substrate (ACS) is proposed, in which the cooling functionality is included in the printed wiring board alongside the electrical wiring. The mechanism for cooling is the use of synthetic jets embedded in the substrate. The utility of the active cooling substrate is demonstrated through quantitative measurements of thermal performance of instrumented platinum heater testbeds. Thermal management is enhanced through the additional heat convection mode introduced by the embedded synthetic jets in the active cooling substrate.© 2003 ASME