Patent Description:
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.

The present invention is specified in the independent claims. Embodiments result from the respective dependent claims. 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 <NUM> 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 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 <NUM> pound per square inch to about <NUM> pounds per square inch
A further embodiment of any of the foregoing embodiments may additionally and/or alternatively includethe 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 <FIG>, there is illustrated an exemplary heat exchanger <NUM>. In an exemplary embodiment, the heat exchanger <NUM> can be a tube-in-tube unified shell (TITUS) heat exchanger <NUM>. The heat exchanger <NUM> can be installed from an exterior of an annular duct <NUM>. The annular duct <NUM> can be defined between an outer case <NUM> enveloping an inner case <NUM> about an axis A. The heat exchanger <NUM> can include multiple small diameter tubes <NUM> assembled as tube-in-tube elements <NUM>. The small diameter tubes <NUM> can have an outside diameter of less than <NUM> inches. An internal working fluid <NUM> that flows through the tube-in-tube elements <NUM> can 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 fluid <NUM>, such as air can be flowing exterior of the tube elements <NUM>, for example in an air duct of a gas turbine engine. In an exemplary embodiment, the internal working fluid <NUM> can be at high pressure, for example ranging from about <NUM> pound per square inch to about <NUM> pounds per square inch.

In an exemplary embodiment, the tube elements <NUM> can be inserted from the exterior of the outer case <NUM> through the outer case <NUM> into the annular duct <NUM>. This design allows for a heat exchanger <NUM> with an orientation and plumbing of the internal working fluid <NUM> to be supplied and returned from one side of the outer case <NUM>, such as the exterior of the annular duct <NUM>. For example, as shown, the internal working fluid <NUM> can be supplied and returned from exterior of the outer case <NUM>.

Referring also to <FIG>, details of the tube-in-tube unified shell elements <NUM> are disclosed. The tube-in-tube unified shell elements or simply TITUS elements <NUM> include an inner tube structure <NUM> disposed within an outer tube structure <NUM>. The inner tube structure <NUM> includes a tubular shaped inner body <NUM> having an internal flow area <NUM>. In an exemplary embodiment, the internal flow area <NUM> can be defined by a smooth bore <NUM> inside diameter of the inner tube structure <NUM>, as seen in <FIG> and <FIG>. The inner tube structure <NUM> includes surface features <NUM> disposed and/or formed on the exterior/outer diameter <NUM> of the inner tube structure <NUM>. In an exemplary embodiment, the surface features <NUM> can be formed as external flutes or guide fins <NUM> that spiral along a portion of the length L of the inner tube structure <NUM> exposed to the working fluid. The inner tube structure <NUM> can be formed from thick walled tube stock. The surface features <NUM> can be machined into shape, such as the spiraling external flutes <NUM>.

A flow passage <NUM> can be defined between any two adjacent flutes <NUM>. The height of flow passage <NUM>, H = (OD-ID)/<NUM> of the annulus defined as the space between the outer tube structure <NUM> and inner tube structure <NUM>, specifically, the inside diameter of the outer tube structure <NUM> shown at the interior surface <NUM> to the outside diameter <NUM> of the inner tube structure <NUM>. The width W of this passage <NUM> is defined as the mean arc length between flutes <NUM>, such that, the aspect ratio, AR = W/H is between <NUM>-<NUM>. The relative angle alpha (α) of the spiral S to the longitudinal axis AA of the inner tube structure <NUM> can be from about between <NUM> degrees (straight) and <NUM> degrees (see <FIG>). The surface features <NUM> are configured to provide the flow passage <NUM> for the internal working fluid <NUM> flowing along the exterior of the inner tube structure <NUM>.

The inner tube structure <NUM> includes a top ring <NUM> shaped as a cylinder configured to couple to the exterior/outer diameter <NUM> proximate an inlet port <NUM> of the inner tube structure <NUM>. The top ring <NUM> facilitates connecting the inner tube structure <NUM> with the outer tube structure <NUM>. The inner tube structure <NUM> includes an outlet port <NUM> opposite the inlet port <NUM>. The internal working fluid <NUM> can enter the inlet port <NUM>, flow through the internal flow area <NUM> and discharge from the outlet port <NUM> of the inner tube structure <NUM>.

The outer tube structure <NUM> includes a longitudinal cylindrical tube wall <NUM>. The tube wall <NUM> of the outer tube structure <NUM> includes an interior surface <NUM> and an exterior surface <NUM> opposite the interior surface <NUM>. The interior surface <NUM> includes an augmentation structure <NUM>. The augmentation structure <NUM> can be formed as helical shaped fins that extend along the interior surface <NUM>. The augmentation structure <NUM> can be formed similarly to rifling of a gun barrel, for example with a helical broaching tool to form ribs. The augmentation structure <NUM> can be continuous or discontinuous. The augmentation structure <NUM> along with the surface features <NUM> are configured to provide vortex boundary mixing for the internal working fluid <NUM> flowing between the exterior of the inner tube structure <NUM> and interior surface <NUM> of the outer tube structure <NUM>. In an exemplary embodiment, micro-fin surface features <NUM> can be formed on the exterior surface <NUM> as seen in <FIG>. The micro-fin surface features <NUM> are configured to increase the surface area of the tube wall <NUM> exterior surface <NUM>. The tube wall <NUM> can have small diameter, or hypodermic tubing with outside diameter (OD) of less than <NUM> inch. The wall thickness can be less than or equal to <NUM> inch, and can be approximately <NUM> inch. The micro-fin surface features can have a thickness of less than or equal to <NUM> inch. In an exemplary embodiment, the micro-fin surface features <NUM> have a height of less than or equal to <NUM> inch. In another exemplary embodiment, the micro-fin surface features <NUM> can range from <NUM> inch to <NUM> inch tall. The micro-fin surface features can have a height/thickness aspect ratio (AR): <NUM> < AR < <NUM>. In an exemplary embodiment, the materials of the tube wall <NUM> can 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 features <NUM> 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 <NUM> includes a first end <NUM> opposite a second end <NUM>. The first end <NUM> connects with the top ring <NUM> proximate the inlet port <NUM> of the inner tube structure <NUM>. The second end <NUM> includes an end cap <NUM> with a hemispherical or domed shape interior surface <NUM>. The end cap <NUM> is configured to turn the internal working fluid <NUM> after exiting the outlet port <NUM>. The internal working fluid <NUM> changes direction and flows through the flow passage <NUM> and in part through a diametral tolerance <NUM> in between the inner tube structure <NUM> and outer tube structure <NUM> toward a flow outlet <NUM> of the outer tube structure <NUM>. As the internal working fluid <NUM> flows through the flow passage <NUM>, the internal working fluid <NUM> is influenced by each of the augmentation structure <NUM>, and the surface features <NUM>, causing the internal working fluid <NUM> to swirl and mix with vortex boundary mixing as depicted in <FIG> by arrows <NUM>. The mixing provides for additional heat transfer between the inner tube structure <NUM> and the outer tube structure <NUM> which lessens the thermal gradient at the second end <NUM>. The diametral tolerance <NUM> is configured to allow for each of the inner tube structure <NUM> and outer tube structure <NUM> to independently expand/contract responsive to thermal gradients. In an exemplary embodiment, the diametral tolerance <NUM> can range from <NUM> inch to <NUM> inch.

In an exemplary embodiment, the internal working fluid <NUM> can discharge out of the flow outlet <NUM> and an additional flow outlet <NUM> as seen in <FIG>. The additional flow outlet <NUM> can be formed in the outer tube structure <NUM>. The additional flow outlet <NUM> would require manifold devices to guide the internal working fluid <NUM>.

The outer tube structure <NUM> includes a top section <NUM> proximate the first end <NUM>. The top section <NUM> includes a flange <NUM> and the flow outlet <NUM>. The tube wall <NUM> of the outer tube structure <NUM> connects with the top section <NUM> proximate the flange <NUM> to form the integral outer tube structure <NUM>. The end cap <NUM> can be connected to the tube wall <NUM> of the outer tube structure <NUM> proximate the second end <NUM>. The outer tube structure <NUM> includes a receiver <NUM> proximate the first end <NUM>. The inner tube structure <NUM> inserts through the receiver <NUM> and connects with the outer tube structure <NUM> via the top ring <NUM>.

The tubular body <NUM> of the inner tube structure <NUM> can be constructed of a thinner wall thickness since the inner tube structure <NUM> does not bear the primary loads created by the gas turbine annular duct fluid flow <NUM>. When the aerodynamic loads applied by the external working fluid <NUM> to the outer case <NUM> cause deflection, the inner case <NUM> and outer case <NUM> structures will come into contact. The interaction between them will form a reinforcement, hence the term unified shell. The inner case <NUM> structure may be a load bearing structure.

In an exemplary embodiment, as seen in <FIG>, a multi-layered manifold <NUM> can be employed to direct the internal working fluid <NUM>. The multi-layered manifold <NUM> can include an inner manifold <NUM> that connects with the outer tube structure <NUM>. A middle manifold <NUM> is connected with the top ring <NUM> forming a first flow space <NUM> for the flow outlet <NUM> and the discharge of the internal working fluid <NUM>. An outer manifold <NUM> is located to form a second flow space <NUM> fluidly coupled to the inlet port <NUM>, for the ingress of the internal working fluid <NUM>.

<FIG> includes a partial cross section view of multiple TITUS elements <NUM> mounted in the outer case <NUM>. The TITUS element <NUM> can be seen with the flange <NUM> connected with the outer case <NUM> in a counter bored portion <NUM>. The counter bored portion <NUM> allows for the flange <NUM> to be set flush with an outer surface <NUM> of the outer case <NUM>. The inner case <NUM> includes an inner surface <NUM>. The inner surface <NUM> includes an inner surface receiver <NUM> for each of the TITUS elements <NUM>. The receiver <NUM> allows for the end cap <NUM> to set within the inner surface receiver <NUM>. There can be a gap <NUM> between the cap <NUM> and the inner surface receiver <NUM>. The gap <NUM> can be from about <NUM> mil to about <NUM> mil. The gap <NUM> allows for thermal expansion of the TITUS element <NUM> and still provides for support to resist vibration from the flow forces of the external working fluid <NUM>, 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.

Claim 1:
A tube-in-tube unified shell element heat exchanger (<NUM>) comprising:
an outer tube structure (<NUM>) comprising a tube wall (<NUM>) defining a first end opposite a second end; the outer tube structure (<NUM>) comprises an interior surface (<NUM>) and an exterior surface (<NUM>) opposite the interior surface (<NUM>);
the outer tube structure (<NUM>) comprises an end cap (<NUM>) connected to the second end of the tube wall (<NUM>); the outer tube structure (<NUM>) comprises a top section proximate the first end; the top section includes a flange (<NUM>) and a flow outlet (<NUM>); the tube wall (<NUM>) of the outer tube structure (<NUM>) connects with the top section proximate the flange (<NUM>) to form an integral outer tube structure;
an inner tube structure (<NUM>) including a tubular shaped inner body defining an internal flow area, the inner tube structure (<NUM>) including surface features (<NUM>) formed on the exterior of the inner tube structure (<NUM>); inner tube structure (<NUM>) includes an outlet port (<NUM>) opposite the inlet port (<NUM>); and
a gap formed between the outer tube structure (<NUM>) and the inner tube structure (<NUM>), the gap fluidly coupled between the inlet port (<NUM>) and the flow outlet (<NUM>), the heat exchanger being characterized in that the interior surface (<NUM>) includes an augmentation structure (<NUM>), in that the inner tube structure (<NUM>) includes a top ring (<NUM>) connected to the exterior proximate an inlet port (<NUM>) of the inner tube structure (<NUM>), and in that the top ring (<NUM>) of the inner tube structure (<NUM>) is connected with the top section of the outer tube structure (<NUM>).