Heat exchanger and fabrication

1. A method for making a heat exchanger assembly, comprising

generating a digital model of the heat exchanger assembly that comprises a heat exchanger core within a housing, said heat exchanger core comprising fluid flow paths;

inputting the digital model into an additive manufacturing apparatus or system comprising an energy source; and

forming the heat exchanger assembly by repeatedly applying energy from the energy source to fuse successively applied incremental quantities of a metal powder corresponding to the digital model of the heat exchanger core and the housing, removing the metal powder from the fluid flow paths, and enclosing the metal powder unfused or partially fused in a first region between the heat exchanger core and the housing.

2. The method of claim 1 , wherein the first region comprises unfused metal powder.

3. The method of claim 1 , wherein the first region comprises partially fused metal powder.

4. The method of claim 1 , wherein the first region encases the heat exchanger core.

5. The method of claim 1 , wherein the assembly further comprises a second region between the heat exchanger core and the housing that is free of metal powder.

6. The method of claim 1 , wherein the assembly further comprises a second region between the heat exchanger core and the housing that comprises partially fused metal powder at a different density than the metal powder in the first region.

7. The method of claim 1 , further comprising forming an enclosure separating the first region from one or more other regions between the heat exchanger core and the housing by repeatedly applying energy from the energy source to fuse successively applied incremental quantities of metal powder.

8. The method of claim 1 , further comprising:

selectively exposing incremental quantities of the metal powder in a layer of a powder bed over a support with a laser or electron beam to fuse the selectively exposed metal powder in a pattern over the support corresponding to a layer of the digital model of the heat exchanger assembly; and

repeatedly providing a layer of the metal powder over the selectively exposed layer and selectively exposing incremental quantities of the metal powder in the layer to fuse the selectively exposed metal powder in a pattern corresponding to another layer of the digital model of the heat exchanger assembly without removing the metal powder from the first region of the heat exchanger assembly.

9. The method of claim 8 , further comprising re-positioning the support between repeated selective exposures of the metal powder to maintain each layer being fused at a fixed position with respect to the laser or electron beam.

10. The method of claim 8 , wherein the first region comprises unfused metal powder in the first region.

11. The method of claim 8 , further comprising forming an enclosure separating the first region from one or more other regions between the heat exchanger core and the housing by repeatedly applying energy from the energy source to fuse successively applied incremental quantities of the metal powder.

12. The method of claim 10 , wherein the removal of the metal powder in fluid flow paths of the heat exchanger core is performed after enclosing the unfused metal powder in the first region.

13. The method of claim 10 , wherein the metal powder in fluid flow paths of the heat exchanger is removed from fluid flow paths of the heat exchanger prior to enclosing the unfused metal powder in the first region, said removal performed selectively to leave unfused metal powder in place in the first region.