Depowdering of an additively manufactured heat exchanger with narrow and turning channels

Abstract

The evolution of heat exchangers (HXs) manufactured by additive manufacturing techniques is significantly needed. The depowdering solution is a necessity, especially if flow channels are incorporated into the design. In this study, a one-piece HX with multiple layers of internal channels (printed by binder jetting additive manufacturing) was completely depowdered through a developed approach. Each HX channel has a semi-elliptical geometry, four perpendicular turnings along the approximately 200-mm length, and an approximately 80-mm center segment that is inaccessible due to the turnings. To depowder this component, two approaches including the compressed air and the vortex motion were tested first. It was found that the compressed air or vortex motion alone could partially depowder the internal unbound powder of the printed heat exchanger. Consequently, for complete depowdering, a combined approach of the vortex motion and compressed air blowing with multiple cycles was developed and tested. A study of the effect of the vortex duration in each depowdering cycle was conducted, and results showed that an increase from five minutes to ten minutes resulted in a reduced number of stages for a complete depowdering.