Aircraft Heat Exchanger
A heat exchanger for heat transfer between an external first flow along a first flowpath and a second flow along an internal second flowpath, has: a first manifold; a second manifold; and a plurality of tubes extending from the first manifold to the second manifold and having respective interiors bounding respective legs of the second flowpath. The plurality of tubes comprises a plurality groups of tubes. For each of the groups of the tubes: the tubes of the group have first ends mounted to the first manifold at respective first locations; and the tubes of the group have second ends mounted to the second manifold at respective second locations. From the first manifold to the second manifold, each tube has: a upstream concave first turn; an upstream convex second turn; and an upstream concave third turn; and the second locations are offset downstream along the first flowpath from the respective first locations.
1 . A heat exchanger for heat transfer between an external first flow along a first flowpath and a second flow along an internal second flowpath, the heat exchanger comprising:
a first manifold;
a second manifold; and
a plurality of tubes extending from the first manifold to the second manifold and having respective interiors bounding respective legs of the second flowpath,
wherein:
the plurality of tubes comprises a plurality groups of tubes;
for each of the groups of the tubes:
the tubes of the group have first ends mounted to the first manifold at respective first locations; and
the tubes of the group have second ends mounted to the second manifold at respective second locations;
from the first manifold to the second manifold, each tube has:
an upstream concave first turn;
an upstream convex second turn; and
an upstream concave third turn; and
the second locations are offset downstream along the first flowpath from the respective first locations.
2 . The heat exchanger of claim 1 wherein:
the groups of tubes form respective stages; and
along the first flowpath the stages are in series; and
along the second flowpath the stages are in parallel.
3 . The heat exchanger of claim 1 wherein:
the second locations are streamwise offset by a distance L O from the respective first locations of at least 10 millimeters or at least 2.0 times a tube outer diameter.
4 . The heat exchanger of claim 1 wherein:
each of the tubes has a centerline lying essentially in a respective plane.
5 . The heat exchanger of claim 1 wherein measured at centerlines of the respective tubes:
the first turns do not extend downstream of the respective first locations by more than 1.0 times a tube nominal outer diameter, if at all;
the second turns extend upstream of the respective first locations by a distance LT of at least 2.0 times the tube nominal outer diameter; and
the third turns do not extend downstream of the respective second locations by more than 1.0 times the tube nominal outer diameter, if at all.
6 . The heat exchanger of claim 1 wherein:
the heat exchanger is a full annulus or an annular segment.
7 . The heat exchanger of claim 1 wherein:
each tube has no turn other than the first turn, the second turn, and the third turn.
8 . A gas turbine engine including the heat exchanger of claim 1 and further comprising:
a fan section having a fan;
at least one compressor section;
a combustor section positioned to receive air compressed by the at least one compressor section; and
a turbine section positioned to receive combustion gas from the combustor to drive the at least one compressor section and the at least one fan section,
wherein:
the heat exchanger is positioned in a bypass flowpath.
9 . The gas turbine engine of claim 8 further comprising:
an epicyclic transmission coupled to the fan; and
a lubrication system having a lubricant flowpath through the epicylic transmission and including the internal second flowpath.
10 . The gas turbine engine of claim 9 further comprising:
a temperature sensor; and
a controller coupled to receive input from the temperature sensor and controlling the lubrication system so as to increase pressure within the tubes responsive to a measured temperature increase.
11 . A method for using the heat exchanger of claim 1 , the method comprising:
driving a first flow along the first flowpath;
driving a second flow along the second flowpath;
measuring a temperature associated with at least one tube of the plurality of tubes; and
controlling pressure within the plurality of tubes so as to increase the pressure responsive to a measured temperature increase.
12 . The method of claim 11 wherein:
the pressure increase counters stress caused by the temperature increase.
13 . The method of claim 11 wherein:
the pressure increase tends to contract the ends of each of the tubes toward each other.
14 . A heat exchanger for heat transfer between an external first flow along a first flowpath and a second flow along an internal second flowpath, the heat exchanger comprising:
a first manifold;
a second manifold; and
a plurality of tubes extending from the first manifold to the second manifold and having respective interiors bounding respective legs of the second flowpath,
wherein:
the plurality of tubes comprises a plurality groups of tubes;
for each of the groups of the tubes:
the tubes of the group have first ends mounted to the first manifold at respective first locations;
the tubes of the group have second ends mounted to the second manifold at respective second locations; and
the second locations are offset downstream along the first flowpath from the respective first locations; and
the tubes are bent so that an internal pressure increase counters stress caused by a temperature increase.
15 . A heat transfer system for heat transfer between an external first flow along a first flowpath and a second flow along an internal second flowpath, the heat transfer system comprising:
a heat exchanger comprising:
a first manifold;
a second manifold; and
a plurality of tubes extending from the first manifold to the second manifold and having respective interiors bounding respective legs of the second flowpath;
at least one temperature sensor positioned to measure a temperature associated with at least one tube of the plurality of tubes;
means for controlling pressure within the plurality of tubes; and
a controller coupled to receive input from the temperature sensor and controlling the means so as to increase the pressure responsive to a measured temperature increase.
16 . The heat transfer system of claim 15 wherein:
the tubes each have a plurality of bends; and
the pressure increase counters stress caused by the temperature increase.
17 . The heat transfer system of claim 15 wherein:
the plurality of tubes comprises a plurality groups of tubes; and
for each of the groups of the tubes:
the tubes of the group have first ends mounted to the first manifold; and
the tubes of the group have second ends mounted to the second manifold.
18 . The heat transfer system of claim 15 wherein:
the at least one temperature sensor is positioned in the first flowpath downstream of the plurality of tubes.
19 . A gas turbine engine including the system of claim 15 and further comprising:
at least one compressor section;
a combustor section positioned to receive air compressed by the at least one compressor section; and
a turbine section positioned to receive combustion gas from the combustor to drive the compressor,
wherein:
the heat exchanger is positioned in a bypass duct.
20 . A method for using the heat transfer system of claim 15 , the method comprising:
driving a first flow along the first flowpath;
driving a second flow along the second flowpath;
measuring a temperature associated with at least one tube of the plurality of tubes; and
controlling pressure within the plurality of tubes so as to increase the pressure responsive to a measured temperature increase.