Moderate Temperature Microlamination: Microchannel Assembly Using Brazing

Why is this technology needed?

Microchannel devices made of low-temperature alloys such as aluminum are not suitable for processes operating at elevated temperatures or pressures, and high-temperature nickel superalloys are prohibitively expensive for many applications. Also, diffusion bonding is not supportive of a low-cost, continuous fabrication process.

How does this technology address the need?

The corrosion resistance and moderate temperature capability of stainless steels enable this material family to satisfy the requirements of a broad range of processes benefiting from microchannel architectures. Lamina architectures employing through-cut features and sheet drawing can be formed without the need for more expensive sheet forming approaches, such as photochemical machining. For bonding, joining a large number of stainless steel laminae using brazing processes offers the potential for a low-cost, repeatable joining process. A variety of braze materials are available for stainless steel brazing. By combining through-cut shims with drawing in a brazed assembly, low-cost microchannel devices can be fabricated for moderate temperature applications (up to 600C).

How is MBI contributing to the solution?

The MBI has fabricated multiple generations of brazed stainless steel heat exchangers, using both photochemical-machined laminae and stamped/drawn versions of these components for reduced cost.

By leveraging capabilities within the MBI and of technology partners, stamped and brazed embodiments of a wide range of moderate-temperature microchannel devices can be designed and fabricated. Figure 1 shows a completed air preheater made from 316L SS. This device is designed to provide a duty of 3.8 kW at 95% effectiveness. Figures 2 and 3 show components prior to assembly and brazing.

Collaborators:

• Dale King
• Steve Leith
• Curt Lavender
• Scott Weil

For additional information . . .

To learn more about this technology, please contact Dale King.