Pulsating Heat Pipe Fin Plates for Enhancing Natural and Forced Convection Cooling of Electronics: Experimental Campaign

Abstract

Several recently patented, air-cooled flat plate pulsating heat pipe designs were prototyped and experimentally tested at typical industrial benchmark conditions. Tests were done for both natural and forced convection conditions to air. Two low-Global Warming Potential working fluids were evaluated, R1233zd(E) and R1234ze(E). Local face temperature measurements were taken by infrared camera visualization of the entire surface of the plate, while the base temperatures at the heater were made by thermocouples. The IR temperature maps provided local details of the cooling surface temperature to better understand the pulsating phenomena and better design the PHP for optimized heat transfer. A heat load of 40W was dissipated per cold plate in natural convection (not the maximum) in the current test condition, giving a thermal performance 30 to 40% higher than the tests done for a plain aluminum plate of the same thickness and size at the same base temperature. For forced convection, the thermal resistance was reduced by 35% by the louvered fin PHP compared to the plain plate, and 60% higher heat loads could be transferred at the same base temperature. This technology is targeted for cooling base plates in compact, high-power telecommunication base stations (network offloading via distributed antenna systems and small cells), especially for 5G technologies, for passive and fan-driven operation. A second application is passive cooling of power electronics, such as base plates of wall-mounted, high voltage junction boxes. Completely passive cooling (passive PHP fluid motion and passive convection to the air) can reduce energy consumption without any need of a fan and make the cooling system "wire-free" for ease in installation, increased reliability, and reduced maintenance.