CPC F28F 1/40 (2013.01) [B23P 15/26 (2013.01); F28D 7/00 (2013.01); F28D 7/022 (2013.01)] | 9 Claims |
1. A method of making a duct comprising:
forming a shell having a tubular form to define an inlet and an outlet of the duct, the duct providing a first flow path within the shell for conveying a first flow between the inlet and the outlet;
forming a heat exchange structure within the shell, the heat exchange structure comprising an intake port formed in the shell, an output port formed in the shell and a second flow path formed within the shell for conveying a second flow between the intake port and the output port,
wherein forming the heat exchange structure comprises forming the second flow path so that it is spirally intertwined with the first flow path for a section of the duct to provide a heat exchanger within the shell of the duct;
wherein forming the heat exchanger structure within the shell includes forming a spiral wall within the shell of the duct to provide an internal structure having a double helix form of spiral channels;
wherein a thickness of the spiral wall is varied such that the thickness of the spiral wall is thinner towards an inside of a bend in the shell, and is wider towards an outside of the bend in the shell.
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