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. (2015). Thermal Performance and Surface Characterization of a Selective Laser Melted Flat-Plate Oscillating Heat Pipe. 26th International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference. Austin, TX. 1719. DOI:10.13140/RG.2.1.4422.2166.

Abstract

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 partially-melted, abraded particles. This study demonstrates the appeal of additive manufacturing for fabrication of customized heat transfer media traditionally challenging to realize.