Thermal Performance and Surface Characterization of a Selective Laser Melted Flat-Plate Oscillating Heat Pipe

Monroe, J.G.
Ibrahim, O.T.
Thompson, S.M.
Shamsaei, N.
Bian, L.
Elwany, A.
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University of Texas at Austin

A titanium alloy (Ti-6Al-4V) flat-plate oscillating heat pipe (FP-OHP) was fabricated using Selective Laser Melting (SLM). The 50.8 x 38.1 x 15.75 mm3 FP-OHP consisted of four integral layers of capillary-sized, circular mini-channels (1.52 mm in diameter). The post-SLM prototype was de-powdered using pressurized air and a novel layer-by-layer, plug-and-pressurize design/approach. A vacuum-grade port was threaded into the FP-OHP, and the heat pipe was charged with acetone (~70% by volume) then hermetically sealed. Experiments were conducted to characterize the thermal performance and functionality of the multi-layered FP-OHP. Results indicate that the acetone-filled FP-OHP operates and can provide for an 800% increase in effective thermal conductivity relative to pure Ti-6Al-4V. The build integrity of the FP-OHP was investigated by shearing along its width to inspect the channel-area surface using field emission scanning electron microscopy (SEM) and laser triangulation for channel topography. The mean surface roughness was found to be approximately 45 micrometers and characterized by partiallymelted, abraded particles. This study demonstrates the appeal of additive manufacturing for fabrication of customized heat transfer media traditionally challenging to realize.