The development of novel heat sinks using selective laser melting

• Main Author: Wong, Matthew
• Published: University of Liverpool 2007
• Subjects: 669
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486445

Heat removal from electronic systems relies on forced convection heat transfer from extended surfaces. The favoured extended surface for avionics enclosures is the cast pin fm array. However, due to the increasing heat dissipation of electronic components, the cooling offered by cylindrical arrays will be insufficient in the near future and higher performance extended surfaces are required. The current study introduces a novel manufacturing technique, Selective Laser Melting (SLM), and' demonstrates its ability to fabricate new designs of extended surface that have not previously been considered, primarily due to their geometric complexity. The SLM processing parameters for aluminium 6061, a new material to the technique, were developed to allow the fabrication ofparts that achieved a density of 90% of the parent metal. Investigations on the SLM-fabricated aluminium 6061 revealed that its thermal conductivity was 75 W/mK, 48% less than the thermal conductivity predicted by standard correlations. 65% of the reduction in thermal conductivity was found to be caused by interparticle thermal resistances, the remainder a result ofporosities. The heat transfer and pressure loss performance of several types of heat sink were characterised by experimental investigations. The extended surfaces manufactured and tested included cylindrical arrays, for validation purposes, elliptical, offset strip and diamond arrays, and various types of lattice. In the acceptable flow rate and pressure drop range, a tightly packed diamond array was found to offer the best performance with a 62% improvement in heat transfer over a typical cylindrical pin arrangement and only 60% ofthe pressure loss. Computational Fluids Dynamic (CFD) studies of the flow in three pin arrangements were conducted to aid visualisation of the fluid flow and to assess the predictive capabilities of Fluent, a commercial CFD code. The CFD pressure loss predictions were within 8 % ofthe experimental results and the heat transfer results were found to be qualitatively meaningful. Results from the experimental and CFD studies indicate that laminar flow in streamlined fm arrays with tight pin spacings offers improved heat transfer performance benefits over turbulent flow in cylindrical arrays at a similar flow rate and pressure drop thereby offering the required improvement in performance for high-power electronic components.