Cross-flow heat exchanger systems and methods for fabrication thereof
A heat exchanger has first and second manifold portions and an array of substantially-parallel heat-transfer tubes extending between the first and second manifold portions. Each heat-transfer tube has an outer surface and an inner surface defining a conduit. In a cross-sectional view, the outer surface of each heat-transfer tube can form a first shape that is non-circular, and the inner surface of heat-transfer tube can form a second shape different than the first shape. Alternatively or additionally, at least one of the first shape and the second shape lacks reflectional symmetry in the cross-sectional view. Methods for fabricating such heat exchangers are also provided.
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.
2. The heat exchanger of claim 1 , wherein:
the first manifold portion is constructed as an inlet for supplying a gas or fluid to the array of first heat-transfer tubes,
the second manifold portion is constructed as an outlet from the array of first heat-transfer tubes, the array of first heat-transfer tubes is constructed to allow a gas or fluid to flow through the array in thermal contact with the outer surfaces of the first heat-transfer tubes, and
the heat exchanger is configured as a cross-flow heat exchanger.
3. The heat exchanger of claim 1 , wherein:
a first pair of spacers of the one or more spacers is disposed proximal to the first ends of the first heat-transfer tubes, the spacers of the first pair being spaced from each other along the first direction by a gap filled with a coupling material, the first ends of the first heat-transfer tubes extending into a first receiving slot of the first manifold portion, at least one of the spacers of the first pair being coupled to a first facing surface of the first manifold portion so as to seal a periphery of the first receiving slot, or
a second pair of spacers of the one or more spacers is disposed proximal to the second ends of the first heat-transfer tubes, the spacers of the second pair being spaced from each other along the first direction by another gap filled with the coupling material, the second ends of the first heat-transfer tubes extending into a second receiving slot of the second manifold portion, at least one of the spacers of the second pair being coupled to a second facing surface of the second manifold portion so as to seal a periphery of the second receiving slot,
wherein the coupling material comprises solder, adhesive, brazing filler metal, or welding filler metal.
4. The heat exchanger of claim 1 , wherein:
a wall of the first manifold portion has a plurality of openings therein, the first end of each first heat-transfer tube being inserted into a corresponding one of the openings in the wall of the first manifold portion, or
a wall of the second manifold portion has a plurality of openings therein, the second end of each first heat-transfer tube being inserted into a corresponding one of the openings in the wall of the second manifold portion.
5. The heat exchanger of claim 1 , wherein:
(a) the first manifold portion comprises a first header and a first mating member having one or more recesses,
a first spacer of the plurality of spacers is disposed proximal to the first ends of the first heat-transfer tubes and coupled to the first header, the first ends of the first heat-transfer tubes being disposed within the first header and opening at a side of the first header opposite the first spacer,
the first mating member is releasably coupled to the first header such that one or more recesses of the first mating member are in fluid communication with one or more of the first ends of the first heat-transfer tubes, and
the side of the first header, which faces and bounds the one or more recesses of the first mating member so as to form the first manifold portion, has the first ends of the first heat-transfer tubes exposed therefrom such that the first ends are in direct fluid communication with the one or more recesses; or
(b) the second manifold portion comprises a second header and a second mating member having one or more recesses,
a second spacer of the plurality of spacers is disposed proximal to the second ends of the first heat-transfer tubes and coupled to the second header, the second ends of the second heat-transfer tubes being disposed within the second header and opening at a side of the second header opposite the second spacer,
the second mating member is releasably coupled to the second header such that one or more recesses of the second mating member are in fluid communication with one or more of the second ends of the first heat-transfer tubes, and
the side of the second header, which faces and bounds the one or more recesses of the second mating member so as to form the second manifold portion, has the second ends of the first heat-transfer tubes exposed therefrom such that the second ends are in direct fluid communication with the one or more recesses.
6. The heat exchanger of claim 1 , further comprising:
a second array of substantially-parallel second heat-transfer tubes extending along the first direction between the first and second manifold portions, a first end of each second heat-transfer tube being in fluid communication with the first manifold portion, a second end of each second heat-transfer tube being in fluid communication with the second manifold portion, each second heat-transfer tube having an outer surface and an inner surface defining a third conduit,
wherein, for each second heat-transfer tube in a cross-sectional view perpendicular to the first direction, the outer surface and the inner surface form respective shapes, and
wherein the shape of the outer surface, the shape of the inner surface, an arrangement of heat-transfer tubes, a pitch between heat-transfer tubes, or any combination thereof for the second array is different than that for the first array.
7. The heat exchanger of claim 1 , wherein at least one of the one or more spacers includes protrusions that project along the first direction from a surface of the corresponding spacer, each protrusion being disposed spaced from and between the plurality of openings in the corresponding spacer.
8. The heat exchanger of claim 7 , wherein each protrusion has a substantially triangular cross-sectional shape and is arranged such that a sloped surface thereof faces an inlet gas or fluid flow external to the array of first heat-transfer tubes.
9. The heat exchanger of claim 1 , wherein:
the array has top and bottom ends, the top end being separated from the bottom end along a direction perpendicular to the first direction and parallel to a direction of gravity; and
at least one of the one or more spacers is arranged at a non-orthogonal angle with respect to the first direction, such that a first end of the at least one spacer at the top end of the array is offset along the first direction from a second end of the at least one spacer at the bottom end of the array.
10. The heat exchanger of claim 9 , further comprising a basin, conduit, or drain disposed with respect to the second end of the at least one spacer so as to capture condensation therefrom.
11. The heat exchanger of claim 1 , further comprising:
a second array of substantially-parallel second heat-transfer tubes extending along the first direction between the first and second manifold portions, a first end of each second heat-transfer tube being in fluid communication with the first manifold portion, a second end of each second heat-transfer tube being in fluid communication with the second manifold portion, each second heat-transfer tube having an outer surface and an inner surface defining a third conduit,
wherein a lateral pitch between the second heat-transfer tubes in the second array along the second direction is different than a lateral pitch between the first heat-transfer tubes in the array along the second direction, or
a vertical pitch between the second heat-transfer tubes in the second array along a third direction perpendicular to the first and second direction is different than a vertical pitch between the first heat-transfer tubes in the array along the third direction.
12. The heat exchanger of claim 1 , wherein:
a ratio of lateral pitch between the first heat-transfer tubes in the array along the second direction to a height of each first heat-transfer tube in the array along a third direction perpendicular to the first and second direction is in a range of 0.75 to 3.0;
a ratio of vertical pitch between the first heat-transfer tubes in the array along the third direction to the height of each first heat-transfer tube in the array along the third direction is in a range of 2.0 to 3.0; and
the height of each first heat-transfer tube in the array along the third direction is in a range of 0.5 mm to 3.0 mm.
13. 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 and an inner surface defining a first 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 and the inner surface forms a second shape, and
both the first shape and the second shape lack reflectional symmetry with respect to all lines in the cross-sectional view.
14. The heat exchanger of claim 13 , wherein at least one of the first shape and the second shape comprises a non-uniform rational B-spline (NURBS).
15. The heat exchanger of claim 13 , wherein:
the first manifold portion is constructed as an inlet for supplying a gas or fluid to the array of first heat-transfer tubes,
the second manifold portion is constructed as an outlet from the array of first heat-transfer tubes,
the array of first heat-transfer tubes is constructed to allow a gas or fluid to flow through the array in thermal contact with the outer surfaces of the first heat-transfer tubes, and
the heat exchanger is configured as a cross-flow heat exchanger.
16. The heat exchanger of claim 13 , further comprising:
a second array of substantially-parallel second heat-transfer tubes extending along the first direction between the first and second manifold portions, a first end of each second heat-transfer tube being in fluid communication with the first manifold portion, a second end of each second heat-transfer tube being in fluid communication with the second manifold portion, each second heat-transfer tube having an outer surface and an inner surface defining a third conduit,
wherein, for each second heat-transfer tube in a cross-sectional view perpendicular to the first direction, the outer surface and the inner surface form respective shapes, and
the shape of the outer surface, the shape of the inner surface, a size of each heat-transfer tube, an arrangement of heat-transfer tubes, a pitch between heat-transfer tubes, or any combination thereof for the second array is different than that for the first array.
17. The heat exchanger of claim 13 , wherein each of the first heat-transfer tubes has only one conduit therein.