Numerical study of a low permeability microporous heat sink for cooling phased-array radar systems

Abstract

Microporous media is being used to develop an improved forced convection cold plate device for removing waste heat from high frequency phased-array radar apertures. The waste heat, generated by transmit and receive microwave functions mounted in separate electronic modules, is conducted to the surfaces of a thin rectangular enclosure (cold plate) through which coolant flows. The performance of the phased-array radar is known to deteriorate very rapidly when the difference in operating temperatures of identical electronic components within each module increases. The cold plate device investigated here, designed to minimize this temperature difference, consists of a microporous layer placed (brazed) within the cold plate. A theoretical transport model is developed around an extended system of two-dimensional equations obtained by considering a thin enclosure and integrating the original three-dimensional equations along the direction of smaller dimension. Thermo/hydraulic characteristics are obtained through numerical simulations considering a low permeability aluminum alloy porous layer, and air, water and PAO as coolants. A theoretical estimate of the global pressure drop across the cold plate is also obtained and compared with the numerical results. The microporous cold plate provides substantially more uniform operating temperature for identical components in all module housings than a cold plate without porous layer. Results also suggest an increased global heat transfer coefficient reducing the operational (junction) temperature of the electronics for the same waste heat.