Session: 12-06-04: Advanced Heat Sinks and Emerging Thermal Applications

Paper Number: 166786

Fabrication and Testing of Microchannel Heat Sinks With Solid and Porous Metallic Surfaces 

Microchannel heat sinks can provide a compact and effective solution for high power cooling applications. Both single-phase convective heat transfer and two-phase flow boiling have been studied by researchers for microchannels. Methods of creating narrow channels vary by channel dimensions and substrate materials. For heat transfer applications, metallic substrates are preferred but silicon wafer has been popular for the available microfabrication processes using photolithography and etching tools. While creating microchannel heat sinks integrated with silicon wafer is possible, widespread adoption in application has not been realized. On the other hand, attempts on creating microchannels on metallic substrates have been very limited by applicable fabrication techniques, especially for high aspect ratio channels commonly used for heat transfer applications.

The present study aims at creating and testing microchannel heat sinks on metallic substrates, with advantages in thermal conductivity, mechanical strength, and machinability. A desktop CNC mill is used on aluminum and copper plates to create microchannels with high aspect ratios and channel widths around 150-200 micrometers. The use of conventional machining tools on metallic materials can significantly reduce costs for materials and fabrication equipment, compared to other microfabrication techniques. Other benefits of metallic substrates include the amenability to add porous surface layers by high temperature sintering of metal powders.  Metallic microchannel heat sinks can be modularized easily for an integration with varying cooling configurations depending on the applications.

In this paper, metallic microchannels will be created with and without porous layers with conventional subtractive CNC machining and powder sintering. Metal powder sintering will be done by a tube furnace, which provides an inert heating environment to prevent oxidization. Porous microchannel samples will be prepared first by machining a recess on the metal substrate, then packing metal powders and sintering, and machining microchannels using the CNC tool.  Suitable parameters for fabrication processes will be identified and presented. The samples will be tested for thermal and hydraulic performance by placing them in a pumped water loop with a heated test section. The test results will be compared with performance data in the literature for microchannel heat sinks created by different fabrication techniques. The primary goals of the current study are demonstrating (1) the use of metallic substrates for microchannel heat sinks, and (2) reduced costs for microchannel fabrication. As a secondary goal, opportunities to create novel microchannel designs will be explored by varying channel dimensions and arrangements. The initial results will provide guidance for further development in sample geometries and testing conditions.

Presenting Author: Younggil Park Florida Polytechnic University

Presenting Author Biography: Younggil Park is an associate professor of mechanical engineering at Florida Polytechnic University. His research interests are compact heat exchangers and thermal systems.

Authors:

Ryan Thomas Florida Polytechnic University
Younggil Park Florida Polytechnic University