Layer Manufacturing of Heat Exchange Elements using Photochemical Machining with Diffusion Brazing 325

A number of heat exchanger elements for a Stirling engine were designed but found to be very difficult to manufacture using conventional technology. Each element required 1800 <1mm oval holes through a 70 mm length of the cooler. The elements were produced by repeated photochemical machining of 185 copper sheets of 0.455 mm thickness and joining them using a process known as diffusion brazing. This paper describes the science and process of manufacturing these components. The procedure was complicated by the need to integrate spigots at each end of the cooler, which meant that some layers required selective diffusion soldering.