Patent ID: 12215930

DETAILED DESCRIPTION

Referring now toFIGS.1-3, there is illustrated an exemplary heat exchanger10. In an exemplary embodiment, the heat exchanger10can be a tube-in-tube unified shell (TITUS) heat exchanger10. The heat exchanger10can be installed from an exterior of an annular duct12. The annular duct12can be defined between an outer case14enveloping an inner case16about an axis A. The heat exchanger10can include multiple small diameter tubes18assembled as tube-in-tube elements20. The small diameter tubes18can have an outside diameter of less than 0.100 inches. An internal working fluid22that flows through the tube-in-tube elements20can include a liquid or a supercritical fluid, such as for example, air (gas), ammonia (liquid/super critical), hydrogen (liquid/super critical), carbon dioxide (super critical), and the like. An external working fluid23, such as air can be flowing exterior of the tube elements20, for example in an air duct of a gas turbine engine. In an exemplary embodiment, the internal working fluid22can be at high pressure, for example ranging from about 1 pound per square inch to about 5000 pounds per square inch.

In an exemplary embodiment, the tube elements20can be inserted from the exterior of the outer case14through the outer case14into the annular duct12. This design allows for a heat exchanger10with an orientation and plumbing of the internal working fluid22to be supplied and returned from one side of the outer case14, such as the exterior of the annular duct12. For example, as shown, the internal working fluid22can be supplied and returned from exterior of the outer case14.

Referring also toFIGS.4-13, details of the tube-in-tube unified shell elements20are disclosed. The tube-in-tube unified shell elements or simply TITUS elements20include an inner tube structure24disposed within an outer tube structure26. The inner tube structure24includes a tubular shaped inner body28having an internal flow area30. In an exemplary embodiment, the internal flow area30can be defined by a smooth bore32inside diameter of the inner tube structure24, as seen inFIGS.5and7. The inner tube structure24includes surface features34disposed and/or formed on the exterior/outer diameter38of the inner tube structure24. In an exemplary embodiment, the surface features34can be formed as external flutes or guide fins34that spiral along a portion of the length L of the inner tube structure24exposed to the working fluid. The inner tube structure24can be formed from thick walled tube stock. The surface features34can be machined into shape, such as the spiraling external flutes34.

A flow passage39can be defined between any two adjacent flutes34. The height of flow passage39, H=(OD−ID)/2 of the annulus defined as the space between the outer tube structure26and inner tube structure24, specifically, the inside diameter of the outer tube structure26shown at the interior surface48to the outside diameter38of the inner tube structure24. The width W of this passage39is defined as the mean arc length between flutes34, 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 structure24can be from about between 0 degrees (straight) and 30 degrees (seeFIG.9). The surface features34are configured to provide the flow passage39for the internal working fluid22flowing along the exterior of the inner tube structure24.

The inner tube structure24includes a top ring40shaped as a cylinder configured to couple to the exterior/outer diameter38proximate an inlet port42of the inner tube structure24. The top ring40facilitates connecting the inner tube structure24with the outer tube structure26. The inner tube structure24includes an outlet port44opposite the inlet port42. The internal working fluid22can enter the inlet port42, flow through the internal flow area30and discharge from the outlet port44of the inner tube structure24.

The outer tube structure26includes a longitudinal cylindrical tube wall46. The tube wall46of the outer tube structure26includes an interior surface48and an exterior surface50opposite the interior surface48. The interior surface48includes an augmentation structure52. The augmentation structure52can be formed as helical shaped fins that extend along the interior surface48. The augmentation structure52can be formed similarly to rifling of a gun barrel, for example with a helical broaching tool to form ribs. The augmentation structure52can be continuous or discontinuous. The augmentation structure52along with the surface features34are configured to provide vortex boundary mixing for the internal working fluid22flowing between the exterior of the inner tube structure24and interior surface48of the outer tube structure26. In an exemplary embodiment, micro-fin surface features54can be formed on the exterior surface50as seen inFIG.11. The micro-fin surface features54are configured to increase the surface area of the tube wall46exterior surface50. The tube wall46can have small diameter, or hypodermic tubing with outside diameter (OD) of less than 0.100 inch. The wall thickness can be less than or equal to 0.010 inch, and can be approximately 0.005 inch. The micro-fin surface features can have a thickness of less than or equal to 0.010 inch. In an exemplary embodiment, the micro-fin surface features54have a height of less than or equal to 0.003 inch. In another exemplary embodiment, the micro-fin surface features54can range from 0.002 inch to 0.010 inch tall. The micro-fin surface features can have a height/thickness aspect ratio (AR): 1<AR<3. In an exemplary embodiment, the materials of the tube wall46can include stainless steel; Inconel®, and Hastelloy®. Inconel® is a class of nickel-chrome-based super alloys characterized by high corrosion resistance, oxidation resistance, strength at high temperatures, and creep resistance. Hastelloy® is a corrosion-resistant nickel alloy that contains other chemical elements such as chromium and molybdenum. This material has high temperature resistance and exceptional corrosion resistance.

The micro-fin surface features54can 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 structure26includes a first end56opposite a second end58. The first end56connects with the top ring40proximate the inlet port42of the inner tube structure24. The second end58includes an end cap60with a hemispherical or domed shape interior surface48. The end cap60is configured to turn the internal working fluid22after exiting the outlet port44. The internal working fluid22changes direction and flows through the flow passage39and in part through a diametral tolerance62in between the inner tube structure24and outer tube structure26toward a flow outlet64of the outer tube structure26. As the internal working fluid22flows through the flow passage39, the internal working fluid22is influenced by each of the augmentation structure52, and the surface features34, causing the internal working fluid22to swirl and mix with vortex boundary mixing as depicted inFIG.10by arrows66. The mixing provides for additional heat transfer between the inner tube structure24and the outer tube structure26which lessens the thermal gradient at the second end58. The diametral tolerance62is configured to allow for each of the inner tube structure24and outer tube structure26to independently expand/contract responsive to thermal gradients. In an exemplary embodiment, the diametral tolerance62can range from 0.002 inch to 0.003 inch.

In an exemplary embodiment, the internal working fluid22can discharge out of the flow outlet64and an additional flow outlet68as seen inFIG.8. The additional flow outlet68can be formed in the outer tube structure26. The additional flow outlet68would require manifold devices to guide the internal working fluid22.

The outer tube structure26includes a top section70proximate the first end56. The top section70includes a flange72and the flow outlet64. The tube wall46of the outer tube structure26connects with the top section70proximate the flange72to form the integral outer tube structure26. The end cap60can be connected to the tube wall46of the outer tube structure26proximate the second end58. The outer tube structure26includes a receiver74proximate the first end56. The inner tube structure24inserts through the receiver74and connects with the outer tube structure26via the top ring40.

The tubular body28of the inner tube structure24can be constructed of a thinner wall thickness since the inner tube structure24does not bear the primary loads created by the gas turbine annular duct fluid flow23. When the aerodynamic loads applied by the external working fluid23to the outer case14cause deflection, the inner case16and outer case14structures will come into contact. The interaction between them will form a reinforcement, hence the term unified shell. The inner case16structure may be a load bearing structure.

In an exemplary embodiment, as seen inFIG.12, a multi-layered manifold78can be employed to direct the internal working fluid22. The multi-layered manifold78can include an inner manifold80that connects with the outer tube structure26. A middle manifold82is connected with the top ring40forming a first flow space84for the flow outlet64and the discharge of the internal working fluid22. An outer manifold86is located to form a second flow space88fluidly coupled to the inlet port42, for the ingress of the internal working fluid22.

FIG.13includes a partial cross section view of multiple TITUS elements20mounted in the outer case14. The TITUS element20can be seen with the flange72connected with the outer case14in a counter bored portion90. The counter bored portion90allows for the flange72to be set flush with an outer surface92of the outer case14. The inner case16includes an inner surface94. The inner surface94includes an inner surface receiver96for each of the TITUS elements20. The receiver96allows for the end cap60to set within the inner surface receiver96. There can be a gap98between the cap60and the inner surface receiver96. The gap98can be from about 10 mil to about 12 mil. The gap98allows for thermal expansion of the TITUS element20and still provides for support to resist vibration from the flow forces of the external working fluid23, such as gas turbine fluid flow during use.

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.