Geometry of heat exchanger with high efficiency

A method for fabricating a heat exchanger, comprising:

• forming through-holes in a plurality of layers, the through-holes having different sizes and locations such that the plurality of layers have gradually varying patterns of the through-holes;
• stacking a first half of the plurality of layers to form a first half of the heat exchanger, such that the through-holes form half of a first flow passage for a first fluid and half of a second flow passage for a second fluid, the second flow passage being physically separated from the first flow passage, the first half of the heat exchanger spanning from a first end of the heat exchanger to a center portion of the heat exchanger, wherein:
• the through-holes are configured and arranged such that each flow passage has at least one parent channel adjacent the first end of the heat exchanger;
• each parent channel is split into a plurality of first sub-channels extending away from the first end of the heat exchanger during a first branching stage;
• a plurality of the first sub-channels are split into a plurality of second sub-channels during a second branching stage, the plurality of second sub-channels extending at a further depth than the plurality of first sub-channels from the first end of the heat exchanger;
• and
• stacking a second half of the plurality of layers in a reverse sequence from the first half of the plurality layers to form a second half of the heat exchanger, the second half and the first half of the heat exchanger being substantially symmetric about the center portion of the heat exchanger.

A method for fabricating a heat exchanger, the method comprising:

• providing metallic powders;
• melting the metallic powders;
• and
• solidifying the melted metallic powders into subsequent layers;
• wherein:
• the layers have through-holes of different sizes and locations such that the plurality of layers have gradually varying patterns of the through-holes;
• the through-holes form a first flow passage for a first fluid and a second flow passage for a second fluid, the second flow passage being physically separated from the first flow passage;
• each of the first and second flow passages has a parent channel near a first end of the heat exchanger;
• each parent channel is split into a plurality of first sub-channels during a first branching stage;
• a plurality of the first sub-channels are split into a plurality of second sub-channels during a second branching stage;
• and
• each flow passage is substantially symmetrical about a center portion of the heat exchanger.