Two-Phase Thermal Ground Planes: Technology Development and Parametric Results

Abstract

Defense Advanced Research Project Agency's (DARPA's) thermal ground plane (TGP) effort was aimed at combining the advantages of vapor chambers or two-dimensional (2D) heat pipes and solid conductors by building thin, high effective thermal conductivity, flat heat pipes out of materials with thermal expansion coefficients that match current electronic devices. In addition to the temperature uniformity and minimal load-driven temperature variations associated with such two phase systems, in their defined parametric space, flat heat pipes are particularly attractive for Department of Defense and commercial systems because they offer a passive, reliable, light-weight, and low-cost path for transferring heat away from high power dissipative components. However, the difference in thermal expansion coefficients between silicon or ceramic microelectronic components and metallic vapor chambers, as well as the need for a planar, chip-size attachment surface for these devices, has limited the use of commercial of the shelf flat heat pipes in this role. The primary TGP goal was to achieve extreme lateral thermal conductivity, in the range of 10 kW/mK–20 kW/mK or approximately 25–50 times higher than copper and 10 times higher than synthetic diamond, with a thickness of 1 mm or less.

Additive manufacturing of heat exchangers: A case study on a multi-layered Ti–6Al–4V oscillating heat pipe

“…However, there are still many challenges in engineering optimal two-phase heat spreaders for high heat flux thermal management [27], including (i) establishing a high thermal conductivity in extreme environments (ii) matching material CTEs at the heat source/spreader junction (iii) and minimizing heat spreader thickness (i.e sub-millimeter). Since simulation and/or modeling of heat transfer and fluid dynamics within TGPs is a challenge in its own right [28] [29], compact form factors [30], channel surface modifications [31,32], utilization of nanofluids [33] and increasing the number of channel layers with respect to FP-OHP thickness [21,25,34].…”

Heat Transfer and Pressure Drop Characteristics of Finned Metal Foam Heat Sinks Under Uniform Impinging Flow

“…Although various advanced cooling systems have been suggested (e.g., thermoelectric cooling, liquid cooling, two-phase cooling, etc.) [2][3][4], the solution with air-cooled heat sinks is preferred because of its reliability and cost-effectiveness [5]. To enhance the rate of heat dissipation from an air-cooled heat sink, the simple approach is to increase heat sink size or the air flow rate.…”

Experimental Development and Computational Optimization of Flat Heat Pipes for CubeSat Applications

“…Thermal conductivity values up to 830 W/m-K have been reported for a polymer-based heat pipe with a thickness of 1 mm [5]. Additionally, the thermal ground plane (TGP) project funded by the Defense Advanced Research Project Agency (DARPA) produced various thin profile vapor chamber designs [6]. Heat fluxes up to 330 W/cm 2 and thermal conductivities as high as 2,100 W/m-K were measured.…”