The present disclosure is directed to tube-in-tube heat exchanger, particularly tube-in-tube unified shell heat exchanger.
Waste heat recovery heat exchangers are annular shaped, tube-style heat exchangers, situated aft of the turbine exit frame. Ideally, the operating fluid enters and exits from the outside diameter of that annulus, due to space constraints. The tubes are long and thin, but need to be rigid. Tubes must be allowed to thermally expand yet be constrained from excessive vibration.
What is needed is a tube-in-tube unified shell heat exchanger that allows simple assembly and plumbing, without the need of complex manifolds.
In accordance with the present disclosure, there is provided a tube-in-tube unified shell element heat exchanger comprising an outer tube structure comprising a tube wall defining a first end opposite a second end; the outer tube structure comprises an interior surface and an exterior surface opposite the interior surface; the interior surface includes an augmentation structure; the outer tube structure comprises an end cap connected to the second end of the tube wall; the outer tube structure comprises a top section proximate the first end; the top section includes a flange and a flow outlet; the tube wall of the outer tube structure connects with the top section proximate the flange to form an integral outer tube structure; an inner tube structure including a tubular shaped inner body defining an internal flow area, the inner tube structure including surface features formed on the exterior of the inner tube structure; the inner tube structure including a top ring connected to the exterior proximate an inlet port of the inner tube structure; inner tube structure includes an outlet port opposite the inlet port; wherein the top ring of the inner tube structure is connected with the top section of the outer tube structure; and a gap formed between the outer tube structure and the inner tube structure, the gap fluidly coupled between the inlet port and the flow outlet.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the augmentation structure comprises helical shaped fins extending along the interior surface.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the surface features comprise external flutes that spiral along a portion of the length of the inner tube structure.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the augmentation structure along with the surface features are configured to provide vortex boundary mixing for an internal working fluid flowing between the exterior of the inner tube structure and interior surface of the outer tube structure.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the gap is configured for each of the inner tube structure and the outer tube structure to independently expand/contract responsive to thermal gradients.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the tube-in-tube unified shell element heat exchanger further comprising micro-fin surface features formed on the exterior surface of the outer tube structure.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the surface features comprise spiraling external flutes having a spiral with a relative angle alpha to a longitudinal axis AA of the inner tube structure being from zero degrees to 30 degrees.
In accordance with the present disclosure, there is provided An annular duct with tube-in-tube unified shell heat exchanger comprising the annular duct defined between an outer case and an inner case about an axis A; multiple tube-in-tube unified shell elements mounted to the outer case and extending into the annular duct radially relative to the axis A; each of the multiple tube-in-tube unified shell elements comprising an outer tube structure comprising a tube wall defining a first end opposite a second end; the outer tube structure comprises an interior surface and an exterior surface opposite the interior surface; the interior surface includes an augmentation structure; the outer tube structure; the outer tube structure comprises an end cap connected to the second end of the tube wall; the outer tube structure comprises a top section proximate the first end; the top section includes a flange and a flow outlet; the tube wall of the outer tube structure connects with the top section proximate the flange to form an integral outer tube structure; an inner tube structure including a tubular shaped inner body defining an internal flow area, the inner tube structure including surface features formed on the exterior of the inner tube structure; the inner tube structure including a top ring connected to the exterior proximate an inlet port of the inner tube structure; inner tube structure includes an outlet port opposite the inlet port; wherein the top ring of the inner tube structure is connected with the top section of the outer tube structure; and a gap formed between the outer tube structure and the inner tube structure, the gap fluidly coupled between the inlet port and the flow outlet.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the augmentation structure comprises helical shaped fins extending along the interior surface.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the surface features comprise external flutes that spiral along a portion of the length of the inner tube structure.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the augmentation structure along with the surface features are configured to provide vortex boundary mixing for an internal working fluid flowing between the exterior of the inner tube structure and interior surface of the outer tube structure.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the gap is configured for each of the inner tube structure and the outer tube structure to independently expand/contract responsive to thermal gradients.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the annular duct with tube-in-tube unified shell heat exchanger further comprising micro-fin surface features formed on the exterior surface of the outer tube structure.
In accordance with the present disclosure, there is provided a process for heat exchange through an annular duct with tube-in-tube unified shell element heat exchanger comprising flowing air through the annular duct defined between an outer case and an inner case about an axis A; mounting multiple tube-in-tube unified shell elements to the outer case extending into the annular duct radially relative to the axis A; each of the multiple tube-in-tube unified shell elements comprising an outer tube structure comprising a tube wall defining a first end opposite a second end; the outer tube structure comprises an interior surface and an exterior surface opposite the interior surface; the interior surface includes an augmentation structure; the outer tube structure; the outer tube structure comprises an end cap connected to the second end of the tube wall; the outer tube structure comprises a top section proximate the first end; the top section includes a flange and a flow outlet; the tube wall of the outer tube structure connects with the top section proximate the flange to form an integral outer tube structure; an inner tube structure including a tubular shaped inner body defining an internal flow area, the inner tube structure including surface features formed on the exterior of the inner tube structure; the inner tube structure including a top ring connected to the exterior proximate an inlet port of the inner tube structure; inner tube structure includes an outlet port opposite the inlet port; wherein the top ring of the inner tube structure is connected with the top section of the outer tube structure; a gap formed between the outer tube structure and the inner tube structure, fluidly coupling the gap between the inlet port and the flow outlet; flowing a working fluid into the inlet port through the inner tube structure; and flowing the working fluid through the gap and out of the flow outlet.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising mounting the flange flush with an outer surface of the outer case.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising forming vortex boundary mixing for the working fluid flowing through the gap past the augmentation structure and the surface features.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising setting the end cap within an inner surface receiver of the inner case; and forming a gap between the cap and the inner surface receiver.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the process further comprising supplying and returning the working fluid from an exterior of the outer case.
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the working fluid is at pressures ranging from about 1 pound per square inch to about 5000 pounds per square inch
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the working fluid is selected from the group consisting of a liquid or a supercritical fluid, air, liquid or super critical phase ammonia, liquid or super critical phase hydrogen, super critical phase carbon dioxide, and the like.
Other details of the heat exchanger are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.
Referring now to
In an exemplary embodiment, the tube elements 20 can be inserted from the exterior of the outer case 14 through the outer case 14 into the annular duct 12. This design allows for a heat exchanger 10 with an orientation and plumbing of the internal working fluid 22 to be supplied and returned from one side of the outer case 14, such as the exterior of the annular duct 12. For example, as shown, the internal working fluid 22 can be supplied and returned from exterior of the outer case 14.
Referring also to
A flow passage 39 can be defined between any two adjacent flutes 34. The height of flow passage 39, H=(OD−ID)/2 of the annulus defined as the space between the outer tube structure 26 and inner tube structure 24, specifically, the inside diameter of the outer tube structure 26 shown at the interior surface 48 to the outside diameter 38 of the inner tube structure 24. The width W of this passage 39 is defined as the mean arc length between flutes 34, such that, the aspect ratio, AR=W/H is between 2-3. The relative angle alpha (α) of the spiral S to the longitudinal axis AA of the inner tube structure 24 can be from about between 0 degrees (straight) and 30 degrees (see
The inner tube structure 24 includes a top ring 40 shaped as a cylinder configured to couple to the exterior/outer diameter 38 proximate an inlet port 42 of the inner tube structure 24. The top ring 40 facilitates connecting the inner tube structure 24 with the outer tube structure 26. The inner tube structure 24 includes an outlet port 44 opposite the inlet port 42. The internal working fluid 22 can enter the inlet port 42, flow through the internal flow area 30 and discharge from the outlet port 44 of the inner tube structure 24.
The outer tube structure 26 includes a longitudinal cylindrical tube wall 46. The tube wall 46 of the outer tube structure 26 includes an interior surface 48 and an exterior surface 50 opposite the interior surface 48. The interior surface 48 includes an augmentation structure 52. The augmentation structure 52 can be formed as helical shaped fins that extend along the interior surface 48. The augmentation structure 52 can be formed similarly to rifling of a gun barrel, for example with a helical broaching tool to form ribs. The augmentation structure 52 can be continuous or discontinuous. The augmentation structure 52 along with the surface features 34 are configured to provide vortex boundary mixing for the internal working fluid 22 flowing between the exterior of the inner tube structure 24 and interior surface 48 of the outer tube structure 26. In an exemplary embodiment, micro-fin surface features 54 can be formed on the exterior surface 50 as seen in
The micro-fin surface features 54 can be formed by use of forge-rolling. Cold forge-rolling is accomplished via use of a center support mandrel. Other processes can include chemical etching/machining of external surface, laser etching or conventional machining, such as on a lathe and machining via wire-EDM.
The outer tube structure 26 includes a first end 56 opposite a second end 58. The first end 56 connects with the top ring 40 proximate the inlet port 42 of the inner tube structure 24. The second end 58 includes an end cap 60 with a hemispherical or domed shape interior surface 48. The end cap 60 is configured to turn the internal working fluid 22 after exiting the outlet port 44. The internal working fluid 22 changes direction and flows through the flow passage 39 and in part through a diametral tolerance 62 in between the inner tube structure 24 and outer tube structure 26 toward a flow outlet 64 of the outer tube structure 26. As the internal working fluid 22 flows through the flow passage 39, the internal working fluid 22 is influenced by each of the augmentation structure 52, and the surface features 34, causing the internal working fluid 22 to swirl and mix with vortex boundary mixing as depicted in
In an exemplary embodiment, the internal working fluid 22 can discharge out of the flow outlet 64 and an additional flow outlet 68 as seen in
The outer tube structure 26 includes a top section 70 proximate the first end 56. The top section 70 includes a flange 72 and the flow outlet 64. The tube wall 46 of the outer tube structure 26 connects with the top section 70 proximate the flange 72 to form the integral outer tube structure 26. The end cap 60 can be connected to the tube wall 46 of the outer tube structure 26 proximate the second end 58. The outer tube structure 26 includes a receiver 74 proximate the first end 56. The inner tube structure 24 inserts through the receiver 74 and connects with the outer tube structure 26 via the top ring 40.
The tubular body 28 of the inner tube structure 24 can be constructed of a thinner wall thickness since the inner tube structure 24 does not bear the primary loads created by the gas turbine annular duct fluid flow 23. When the aerodynamic loads applied by the external working fluid 23 to the outer case 14 cause deflection, the inner case 16 and outer case 14 structures will come into contact. The interaction between them will form a reinforcement, hence the term unified shell. The inner case 16 structure may be a load bearing structure.
In an exemplary embodiment, as seen in
A technical advantage of the disclosed heat exchanger includes a double-walled tube structure, making the TITUS element structurally stiff.
Another technical advantage of the disclosed heat exchanger includes fluid entering from the top, through the inner tube, to the bottom; at the bottom, the fluid travels up between the inner and outer tubes.
Another technical advantage of the disclosed heat exchanger includes inside the annular passage are turbulator ribs that enhance heat transfer.
Another technical advantage of the disclosed heat exchanger includes processed flow is collected at the top; hence, fluid enters and exits from the same end of the tube structure.
Another technical advantage of the disclosed heat exchanger includes the outer tube contains forge rolled fins, or threads, to increase surface area and heat transfer.
Another technical advantage of the disclosed heat exchanger includes TITUS elements having free floating ends allowing for thermal expansion, unlike conventional tube-style heat exchangers having the tubes fixed at both ends, requiring some means of compliance to alleviate thermal strain.
Another technical advantage of the disclosed heat exchanger includes the TITUS element allows for simple assembly and plumbing, without the need of complex manifolds.
Another technical advantage of the disclosed heat exchanger includes the entire TITUS element, and its internal components, are allowed to grow radially without inducing thermal strain.
Another technical advantage of the disclosed heat exchanger includes the TITUS element is simply supported with a slip-fitting.
Another technical advantage of the disclosed heat exchanger includes TITUS elements are compact allowing for multiple end use such as for oil coolers or fuel cooling and used as immersive heaters/coolers.
There has been provided a heat exchanger. While the heat exchanger has been described in the context of specific embodiments thereof, other unforeseen alternatives, modifications, and variations may become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.