The Manufacture of Micro Cross-Flow Heat Exchangers by Selective Laser Melting

Abstract

Selective Laser Melting, a layer-based Solid Freeform Fabrication process, has been used to fabricate micro crossflow heat exchangers from 316L Stainless Steel powder. Selective Laser Melting (SLM) technology is based on automated layer additive fabrication and represents a departure from the existing manufacturing techniques for micro heat exchangers, such as precision machining, chemical etching and diffusion bonding. The Selective Laser Melting technique uses a 100-Watt Ytterbium fibre laser to fully melt a pre-deposited layer of a single component metallic powder onto a substrate according to a computer-generated pattern. By successive powder deposition of these layers at 50 microns thickness, fully dense, micro cross-flow heat exchangers have been built. Micro heat exchangers involving heat transfer and flow in microchannels have found applications in highly specialised areas such as microelectronics cooling, aerospace, microfabricated fluidic systems, and biomedical processes where lightweight, small volume heat exchangers are required. The Selective Laser Melting technique can provide custom-designed micro heat exchangers fabricated from stainless steel or copper in special geometries not possible by any other manufacturing method. SLM allows the heat exchanger plate wall thickness, as well as channel dimensions and geometries to be carefully controlled in the range of 150 to 750 microns with a typical surface roughness, Ra, of 15 microns. The prototype micro heat exchanger tested in this study provided an overall heat transfer coefficient 2.22 kW/m