High-Temperature Water Heat Pipes

High Temperature Electronics require innovative thermal management devices. Copper water heat pipes are a well-established solution for many conventional electronics cooling applications; however they have several problems when applied to high temperature electronics. The high vapor pressure of the working fluid combined with the decreasing strength of an already soft material leads to excessive wall thickness, high mass, and an inability to make thermally useful structures such as planar heat pipes (vapor chambers) or heat pipes with flat input surfaces. Recent work has shown that titanium/water and Monel/water heat pipes can overcome the disadvantages of copper/water heat pipes and produce a viable thermal management solution for high temperature electronics. A study has shown that water remains the fluid of choice due to its favorable transport properties. Monel and titanium offer much higher strength and result in reasonable wall thickness and mass. Testing has shown compatibility at high temperature. Presented in this paper are a survey of potential replacement fluids, results from high-temperature life testing of water in Monel and titanium envelopes, and comparison of mass and performance with competing approaches such as copper/water.