| CPC F28D 7/16 (2013.01) [B23P 15/26 (2013.01); F28F 9/02 (2013.01)] | 17 Claims |

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1. A heat exchanger comprising:
first and second manifold portions;
an array of substantially-parallel first heat-transfer tubes between the first and second manifold portions, each first heat-transfer tube extends along a first direction, a first end of each first heat-transfer tube being in fluid communication with the first manifold portion, a second end of each first heat-transfer tube being in fluid communication with the second manifold portion, each first heat-transfer tube having an outer surface, a first inner surface defining a first conduit, and a second inner surface defining a second conduit; and
one or more spacers disposed along the array of first heat-transfer tubes between the first and second manifold portions, each spacer having a plurality of openings therein, each first heat-transfer tube passing through a corresponding one of the openings in each spacer,
wherein, for each first heat-transfer tube in a cross-sectional view perpendicular to the first direction:
the outer surface forms a first shape that is non-circular, the first shape having a leading bulbous end and a tapered tail end, the first conduit being a closest conduit to the leading bulbous end,
the first shape has reflectional symmetry with respect to a lateral axis extending along a second direction perpendicular to the first direction,
the first inner surface forms a second shape different than the first shape, the second shape having reflectional symmetry with itself with respect to the lateral axis,
the first shape is a droplet shape,
the second inner surface forms a third shape in the cross-sectional view different than the first shape, and
both the second shape and the third shape are circles or ellipses, and
wherein each of the first heat-transfer tubes has only two conduits therein.
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