Fractal heat exchanger with bypass

1. A heat exchanger comprising:

a plurality of first fluid channels defining a flow path for a first fluid;

a first fractal channel for conveying the first fluid to the plurality of first fluid channels; and

a second fractal channel for conveying the first fluid from the plurality of first fluid channels;

wherein the first fractal channel and the second fractal channel each comprises at least one divergence point along its length where a parent channel splits into a plurality of sub-channels which diverge away from each other, and

wherein one or each of the first fractal channel and the second fractal channel defines one or more through-channels for a second fluid to pass through the respective fractal channel, each through-channel extending from a parent channel side of a divergence point and emerging between the corresponding sub-channels on a sub-channel side of the divergence point.

2. The heat exchanger according to claim 1 , wherein the first fractal channel and the second fractal channel each comprises a plurality of fractal stages wherein each fractal stage comprises at least one parent channel, a divergence point and a plurality of sub-channels, and wherein the plurality of sub-channels of one fractal stage form parent channels of a subsequent fractal stage.

3. The heat exchanger according to claim 2 , wherein the sub-channels of each fractal stage are distributed in a grid configuration.

4. The heat exchanger according to claim 2 , wherein the sub-channels of each fractal stage are shaped such that at least a portion of each sub-channel is parallel to a common axis.

5. The heat exchanger according to claim 1 , wherein a cross-sectional area of each parent channel is equal to a total cross-sectional area of its corresponding sub-channels.

6. The heat exchanger according to claim 1 , wherein each through-channel is axially aligned with at least a portion of the parent channel.

7. The heat exchanger according to claim 1 , wherein a through-channel is provided for each parent channel at each divergence point of the first fractal channel and the second fractal channel.

8. The heat exchanger according to claim 1 , wherein the plurality of first fluid channels are a plurality of discrete tubes directly connected to the first fractal channel and the second fractal channel.

9. A heat exchanger according to claim 1 , comprising a heat exchanger core including the plurality of first fluid channels and a plurality of second fluid channels defining a flow path for the second fluid.

10. The heat exchanger according to claim 9 , wherein the heat exchanger comprises a homogeneous block of material having a plurality of bores extending therethrough defining the plurality of first fluid channels and second fluid channels, optionally wherein the first fluid channels and the second fluid channels are arranged in an alternating fashion.

11. The heat exchanger according to claim 9 , wherein the plurality of channels in the heat exchanger core each have a diamond-shaped cross-section.

12. The heat exchanger according to claim 1 , further comprising an outer wall defining a second fluid inlet and a second fluid outlet for a second fluid to flow through the heat exchanger and exchange heat with the plurality of first fluid channels, wherein the fluid inlet and the fluid outlet are axially aligned with each other along a longitudinal axis of the heat exchanger.

13. The heat exchanger according to claim 12 , further comprising:

a first fluid inlet conduit connected to the first fractal channel; and

a first fluid outlet conduit connected to the second fractal channel, the first fluid inlet and outlet conduits both extending through the outer wall.

14. A heat exchanger according to claim 13 , wherein the fluid inlet conduit and the fluid outlet conduit are at an angle of between 45 and 90 degrees with respect to a longitudinal axis the heat exchanger.

15. A method comprising:

manufacturing a heat exchanger according claim 1 by a process of additive manufacturing as one piece.