Heat exchanger

1. A method of manufacturing a heat exchanger, comprising:

forming a layer of the heat exchanger, forming including:

stamping a series of regular corrugations with a predetermined period into a metal sheet to form a corrugated sheet; and

skipping a corrugation stamping step so as to create a space between two adjacent corrugations in the corrugated sheet which are thus separated by greater than the predetermined period, and thereby create at least a part of a de-congealing channel.

2. The method as claimed in claim 1 , further comprising

repeating the step of forming a layer so as to form a first plurality of layers for a flow of oil therethrough,

providing a second plurality of layers for a flow of fluid therethrough, and

forming the heat exchanger by alternating layers of the first and second pluralities of layers so that in use oil in the first plurality of layers is in a heat exchanging relationship with fluid in the second plurality of layers.

3. The method as claimed in claim 2 , wherein forming the heat exchanger comprises providing intervening separators between the layers of the first plurality of layers.

4. The method as claimed in claim 1 , wherein the step of forming a layer of the heat exchanger by stamping the metal sheet comprises stamping the sheet in a first upward direction and in a second downward direction so as to form the corrugations.

5. The method of claim 1 , wherein each corrugation has an oscillating geometry along a length of the corrugation across a width of the corrugated sheet.

6. The method of claim 1 , wherein each corrugation comprises an opening for fluid communication between the corrugations.

7. The method of claim 1 , wherein the de-congealing channel is formed between two of the first plurality of layers.