US20150300745A1 - Counterflow helical heat exchanger - Google Patents

Abstract

A heat exchanger assembly comprising a tube with a thermally conductive tube insert sealed therein, the tube insert having a substantially similar cross-section to the cross-section of the tube, and a plurality of fluid ports for passage of fluid into and out of the tube, the fluid ports arranged for counterflow operation. The tube insert includes a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends, each of the first ends offset from the other by a predetermined angle and each of the second ends offset from the other by a predetermined angle. The tube insert is sealed within the tube to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices.

Description

RELATED APPLICATIONS
• This application claims priority to U.S. Application No. 61/980,274, filed on Apr. 16, 2014.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to heat exchangers and, more particularly, to liquid-to-liquid heat exchangers for use in comparatively smaller spaces, such as in automobiles or other motor vehicles.
• 2. Description of Related Art
• Designers of heat exchangers for use in automobiles and other motor vehicles are constantly striving to obtain increased heat transfer capability in a smaller space. In the field of liquid-to-liquid heat exchangers, the use of turbulators on the hot fluid side and extended surface, such as a sintered metal matrix, on the cool fluid side, are well-known approaches to the problem. Increasing the flow path length of the fluids while maintaining reasonable fluid pressure drops is another approach to increased heat transfer, but it is not usually possible to accomplish this in a smaller space.
• Therefore, a need exists for an improved heat exchanger with superior heat transfer capabilities, which would provide for optimum performance at the least possible cost while utilizing standard liquid-to-liquid heat exchanger manufacturing techniques, and providing the same in an equivalent- or smaller-sized package.
SUMMARY OF THE INVENTION
• Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved heat exchanger assembly which can provide equivalent or superior heat transfer performance in a smaller package.
• It is another object of the present invention to provide an improved heat exchanger which provides a considerable increase in flow path length, and consequently an increase in heat transfer, for a given tube length.
• A further object of the invention is to provide an improved heat exchanger which allows for counterflow operation, providing optimum heat transfer performance.
• It is yet another object of the present invention to provide an improved heat exchanger which makes use of standard aluminum liquid-to-liquid heat exchanger manufacturing techniques, such as inner tube expansion and cab (controlled atmosphere brazing) furnace flux brazing.
• It is still another object of the present invention to provide an improved heat exchanger which includes a helical tube insert, thereby creating two fluid-tight fluid flow paths, each with considerably increased length, within the tube.
• Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
• The above and other objects, which will be apparent to those skilled in the art, are achieved in the present invention which is directed to a helical heat exchanger assembly comprising a tube having first and second ends, a length, an inner diameter and a cross-section incorporating the inner diameter. The helical heat exchanger assembly includes a thermally conductive tube insert having first and second ends and a length therebetween and a substantially similar cross-section to the cross-section of the tube, and a plurality of inlet and outlet fluid ports for passage of a first and second fluid into and out of the tube. The tube insert includes a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends. Each of the helices' first ends is offset from the other by a predetermined angle and each of the second ends is offset from the other by a predetermined angle. The tube insert is sealed within the tube to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices.
• The fluid ports may be arranged for counterflow operation, whereby the first and second fluids flow in opposite directions. At least one of the inlet or outlet fluid ports in a set of fluid ports may positioned in an opening in a wall of the tube, or alternatively, at least one of the inlet or outlet fluid ports in a set of fluid ports may be positioned on an end of the tube. The first ends of the helices may be offset from each other by an angle of 180 degrees, and each of the helices may have a predetermined pitch which is less than the tube inner diameter. At least one of the helices may include turbulating dimples or ridges.
• Each of the tube and tube insert may have a substantially circular cross-section. The tube insert may be sealed inside the tube such that the tube insert does not extend substantially beyond the tube first or second ends, and the assembly may include a first end cap sealed to the tube and tube insert first ends and a second end cap sealed to the tube and tube insert second ends. The first and second end caps may be flat, circular plates and may be sealed flush with the ends of the tube and tube insert to prevent fluid mixing inside the heat exchanger.
• The tube insert may include an inner expansion tube having first and second ends and a length therebetween and a diameter less than the tube insert outer diameter, the helices extending along the length of and winding around the inner expansion tube. The inner expansion tube is capable of receiving an expansion mandrel inserted therein to expand the tube insert into a tight fit with an inner surface of the tube. The tube may include a first end cap sealed to the tube, tube insert and inner expansion tube first ends, respectively, and a second end cap sealed to the tube, tube insert and inner expansion tube second ends, respectively. The first and second end caps may be flat, circular plates and may be sealed flush with the ends of the tube, tube insert and inner expansion tube to prevent fluid mixing inside the heat exchanger.
• The tube and tube insert may each be comprised of braze-clad aluminum, and the helices and tube may be brazed together to create fluid-tight first and second fluid flow paths.
• The helical heat exchanger assembly may include a plurality of tubes with tube inserts sealed therein, the first fluid inlet ports of each tube arranged in parallel and the second fluid inlet ports of each tube arranged in parallel, and the first fluid outlet ports of each tube arranged in parallel and the second fluid outlet ports of each tube arranged in parallel. The assembly may further include a first inlet manifold connecting each of the first fluid inlet ports, the first inlet manifold including a fluid inlet port for passage of a first fluid into the heat exchanger assembly, a first outlet manifold connecting each of the first fluid outlet ports, the first outlet manifold including a fluid outlet port for passage of a first fluid out of the heat exchanger assembly, a second inlet manifold connecting each of the second fluid inlet ports, the second inlet manifold including a fluid inlet port for passage of a second fluid into the heat exchanger assembly, and a second outlet manifold connecting each of the second fluid outlet ports, the second outlet manifold including a fluid outlet port for passage of a second fluid out of the heat exchanger assembly, wherein the inlet and outlet manifolds are each sealed to prevent fluid mixing inside the heat exchanger assembly.
• The first and second inlet and outlet manifold fluid ports may be arranged for counterflow operation whereby the first and second fluids flow in opposite directions.
• In another aspect, the present invention is directed to a method of assembling a heat exchanger, comprising the steps of providing a tube having first and second ends, a length, an inner diameter and a cross-section incorporating the inner diameter. The method includes providing a thermally conductive tube insert having first and second ends, a length and a substantially similar cross-section to the cross-section of the tube, the tube insert including a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends, each of the first ends offset from the other by a predetermined angle and each of the second ends offset from the other by a predetermined angle, and inserting the tube insert within the tube and sealing the tube insert therein to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices. The method further includes providing a plurality of inlet and outlet fluid ports for passage of a first and second fluid into and out of the tube.
• The fluid ports may be arranged for counterflow operation, whereby the first and second fluids flow in opposite directions. Each of the first ends of the helices may be offset from the other by an angle of 180 degrees and each of the second ends of the helices may be offset from the other by an angle of 180 degrees, and each of the helices may have a predetermined pitch which is less than the tube inner diameter. At least one of the helices may include turbulating dimples or ridges.
• Each of the tube and tube insert may have a substantially circular cross-section and the tube insert may be inserted within the tube by automation. The tube insert may be inserted within the tube such that the tube insert does not extend substantially beyond the tube first or second ends, and the method may further include the steps of sealing a second end cap to the tube and tube insert second ends and sealing a first end cap to the tube and tube insert first ends, respectively. The first and second end caps may be flat, circular plates and may be sealed flush with the ends of the tube and tube insert to prevent fluid mixing inside the heat exchanger.
• The tube insert may include an inner expansion tube having first and second ends, a length and a diameter less than the tube insert outer diameter, the helices extending along the length of and winding around the inner expansion tube. The inner expansion tube is capable of receiving an expansion mandrel inserted therein to expand the tube insert into a tight fit with an inner surface of the tube. The method may further include the step of inserting the expansion mandrel into the inner expansion tube and expanding the tube insert until an outer surface of the tube insert is a tight fit against an inner surface of the tube. The method may then include sealing a second end cap to the tube, tube insert, and inner expansion tube second ends and sealing a first end cap to the tube, tube insert, and inner expansion tube first ends, respectively. The first and second end caps may be flat, circular plates and may be sealed flush with the ends of the tube, tube insert and inner expansion tube to prevent fluid mixing inside the heat exchanger.
• The tube and tube insert may each be comprised of braze-clad aluminum, and the method may further include the step of brazing the heat exchanger in a cab (controlled atmosphere brazing) furnace to create fluid-tight first and second fluid flow paths.
• In yet another aspect, the present invention is directed to a method of operating a heat exchanger assembly, comprising the steps of providing a heat exchanger having a tube with first and second ends, a length, an inner diameter and a cross-section incorporating the inner diameter. The heat exchanger includes a thermally conductive tube insert having a length and a substantially similar cross-section to the cross-section of the tube, the tube insert including a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends, each of the first ends offset from the other by a predetermined angle and each of the second ends offset from the other by a predetermined angle. The tube insert is sealed within the tube to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices. The heat exchanger further includes a plurality of inlet and outlet fluid ports for passage of a first and second fluid into and out of the tube. The method includes connecting inlet and outlet fluid lines for a first fluid to a first set of inlet and outlet ports, connecting inlet and outlet fluid lines for a second fluid to a second set of inlet and outlet ports, and flowing the first and second fluids through the first and second sets of inlet and outlet ports, respectively, to cool one of the fluids.
• The first and second sets of inlet and outlet fluid ports may be arranged for counterflow operation, whereby the first and second fluids flow in opposite directions through the first and second fluid paths between the helices.
BRIEF DESCRIPTION OF THE DRAWINGS
• The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:
• FIG. 1 depicts a perspective view of one embodiment of the heat exchanger with helical tube insert according to the present invention;
• FIG. 2 depicts an exploded perspective view of the heat exchanger with helical tube insert according to the present invention, as shown inFIG. 1;
• FIG. 3 depicts a perspective view of one embodiment of the helical tube insert according to the present invention, as shown inFIG. 2;
• FIG. 4A depicts a top cross-sectional view of another embodiment of the heat exchanger with helical tube insert;
• FIG. 4B depicts an end view of the upper portion of the heat exchanger with helical tube insert ofFIG. 4A, showing a first fluid outlet port and a second fluid inlet port;
• FIG. 5 depicts a top plan view of a portion of the helical tube insert according to the present invention as shown inFIG. 4A, taken along length L3; and
• FIG. 6 depicts a top plan view of another embodiment of the helical tube insert according to the present invention, wherein each of the helices includes turbulating dimples or ridges.
• FIG. 7 depicts a perspective view of one embodiment of the heat exchanger assembly including multiple helical heat exchangers arranged in parallel and connected by inlet and outlet manifolds, according to the present invention;
• FIG. 8 depicts a cross-sectional view of the embodiment of the heat exchanger assembly shown inFIG. 7, taken along section B-B; and
• FIG. 9 depicts a cross-sectional view of the embodiment of the heat exchanger assembly shown inFIG. 7, taken along section A-A.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
• In describing the embodiment of the present invention, reference will be made herein toFIGS. 1-9 of the drawings in which like numerals refer to like features of the invention.
• The present invention is directed to a heat exchanger assembly including a heat exchanger tube and a helical tube insert. The helical tube insert is sealed within a tube of substantially similar cross-section, thereby creating two distinct fluid flow paths within the tube. The pitch of the helical convolutions is less than or equal to the inner diameter of the tube, in order to obtain fluid flow paths of increased length over that of a conventional liquid-to-liquid heat exchanger tube. The ends of the heat exchanger tube are capped and the tube is fitted with inlet and outlet fluid ports for each of the two fluid flow paths. The flow paths within the heat exchanger assembly of the present invention may be parallel flow or co-current (where the fluids move in the same direction), or counterflow (where the direction of the flow of one working fluid is opposite the direction of the flow of the other fluid.) In parallel flow heat exchangers, the outlet temperature of the “hot” fluid can never become lower than the outlet temperature of the “cold” fluid, and the exchanger is performing at its best when the outlet temperatures are equal. Counterflow heat exchangers are inherently more efficient than parallel flow heat exchangers and have several significant advantages over a parallel flow design. The more uniform temperature difference between the two fluids minimizes the thermal stresses throughout the heat exchanger, the outlet temperature of the “hot” fluid can become considerably lower than the outlet temperature of the “cold” fluid and can actually approach the inlet temperature of the “cold” fluid, and the more uniform temperature difference produces a more uniform rate of heat transfer throughout the heat exchanger, over the entire length of the fluid flow path. The fluid connection fittings of the present invention may be arranged for counterflow operation for optimum heat transfer performance.
• Certain terminology is used herein for convenience only and is not to be taken as a limitation of the invention. For example, words such as “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configuration shown in the drawings. For purposes of clarity, the same reference numbers may be used in the drawings to identify similar elements.
• Referring now toFIG. 1, a perspective view of one embodiment of the helical heat exchanger assembly of the present invention is shown. The assembly includes atube10 of substantially circular cross-section, having a length L1 and first and second ends (not shown), and a helical tube insert (not shown) of substantially similar cross-section sealed therein. Tubes having a circular-shaped axial cross-section (i.e. perpendicular to the axis of the tube) are typically utilized for optimum heat transfer performance of the heat exchanger, although other tube shapes and cross-sections may also be utilized to achieve the objects of the present invention. The ends of thetube10 may be sealed by afirst end cap14 andsecond end cap24 to form a self-contained heat exchanger assembly unit. Preferably, the end caps14,24 are flat, circular plates which are sealed flush with the ends of the tube and helical tube insert to prevent fluid mixing at the interior ends of the heat exchanger unit. The first and second end caps14,24 may be secured and sealed to the respective ends of the tube by welding, solder baking, brazing or other equivalent process known to those in the art.
• Tube10 includes a plurality of inlet and outlet fluid ports for passage of fluid into and out of the heat exchanger assembly. As shown inFIG. 1, the heat exchanger assembly of the present invention includes a firstfluid inlet port40 andoutlet port42, and a secondfluid inlet port50 andoutlet port52. The first fluid flow path is depicted indirection41, and the second fluid flow path is depicted indirection51. As shown inFIG. 2, the fluid connection fittings as described above may be inserted into alignedopenings30 in the wall of thetube10 and arranged for counterflow operation. The fluid connection fittings are positioned per design requirements, and alternatively may be positioned, for example, on either ends of the tube, as shown in the upper portion ofFIG. 4A and inFIG. 4B, so long as the fittings are arranged for counterflow operation.
• Referring now toFIG. 2, an exploded perspective view of the heat exchanger assembly of the present invention, including ahelical tube insert100, is shown.Tube insert100 has first and second ends101,102, a length L2 and a substantially similar cross-section to that oftube10, and is comprised of twohelices120,130 extending along the length L2 oftube insert100 and offset from each other by a predetermined distance d. Each of the helices has afirst end121,131 and asecond end124,134 (FIG. 6.) As shown inFIGS. 2,4A and4B, in a normal configuration, helices first ends121,131 are adjacent tube insertfirst end101, and helices second ends124,134 are adjacent tube insertsecond end102. The first ends of each of the helices are offset from each other by a predetermined angle, such as an angle of 180 degrees, as they contacttube end cap14 and the second ends of each of the helices are offset from each other by a predetermined angle (preferably the same angle as for the first ends) as they contact tube end cap24 (FIG. 4B.) In the embodiments shown inFIGS. 2 and 4A, the pitch p of the helical convolutions of each of thehelices120,130 is less than the inner diameter D1 of theheat exchanger tube10, thereby creating two fluid flow paths, each with substantially increased length over that of a typical heat exchanger tube. Alternatively, the pitch p of each of the helical convolutions may be greater than or equal to the inner diameter D1 ofheat exchanger tube10; however such a configuration will result in a shorter fluid flow path than if the pitch p were less than the inner diameter D1 of thetube10. The pitch of the helical convolution is defined as the axial advance of a point during one complete rotation.
• As further shown inFIG. 2, thehelical tube insert100 may have an outer diameter D2 which is nominally smaller than the inner diameter D1 oftube10, to allow for a sliding fit therein. During assembly of the heat exchanger,tube insert100 is slideably inserted into afirst tube end12 in the direction of asecond tube end22. As shown inFIGS. 1-4A,tube insert100 does not extend substantially beyond the first and second tube ends12,22, after insertion intotube10.Tube insert100 may be installed manually or by automation during assembly of the heat exchanger unit. After installation, end caps14,24 are sealed to tube ends12,22, tube insert ends101,102, and helices ends121,131,124,134, respectively, to form fluid-tightfluid flow paths41,51 inside the heat exchanger assembly (FIG. 4A.)
• As shown inFIG. 2, and more particularly shown inFIG. 3, in an embodiment of the invention, the first ends121,131 of the windings ofhelices120,130 are offset from each other by an angle of 180 degrees, and the helices extend along the length of and are wound around aninner expansion tube110 of relatively small diameter. As further shown inFIG. 3, the second ends124 and134 (not shown) ofhelices120,130 are also offset from each other by an angle of180 degrees.Inner expansion tube110 has afirst end111 adjacent tube insertfirst end101 and asecond end112 adjacent tube insert second end102 (FIG. 4A.) As shown inFIG. 4A,inner expansion tube110 has a length substantially equal to the lengths L1, L2 oftube10 andtube insert100.
• FIG. 4A depicts a top cross-sectional view of another embodiment of the assembled heat exchanger with helical tube insert, showing fluid inlet and outlet ports positioned in the wall of the tube and on one end of the tube, respectively, and arranged for counterflow operation. As shown inFIG. 4A, each ofhelices120,130 has afirst side122,132 and asecond side123,133. The respective first122,132 andsecond sides123,133 of the helices are offset by a predetermined distance d along the length oftube insert100, creating two distinctfluid flow paths41,51 between the helical convolutions. Firstfluid flow path41 begins attube inlet40 and ends attube outlet42, and is defined between thesecond sides123,133 of the helices, while secondfluid flow path51 begins attube inlet50 and ends attube outlet52 and is defined between thefirst sides122,132 of the helices. The pitch p of the helical convolutions of each of thehelices120,130 is less than the inner diameter D1 of theheat exchanger tube10, thereby creating two fluid flow paths, each with substantially increased length over that of a typical heat exchanger tube. As shown in the bottom portion ofFIG. 4A, firstfluid inlet port40 and secondfluid outlet port52 are positioned in openings in the wall oftube10. Fluid connection fittings positioned other than in openings in the wall of the tube may also be used, for example, fittings and connections at the ends oftube10, as shown in the upper portion ofFIG. 4A, and more particularly shown inFIG. 4B.
• FIG. 4B shows an end view of the upper portion ofFIG. 4A, showing firstfluid outlet port42 and secondfluid inlet port50 disposed on and integral withend cap24.Fluid connection fittings40,42,50,52 are shown arranged for counterflow operation. In operation of the heat exchanger, inlet and outlet fluid lines (not shown) for firstfluid flow path41 are connected to inlet andoutlet ports40 and42, respectively, and inlet and outlet fluid lines (not shown) for secondfluid flow path51 are connected to inlet andoutlet ports50 and52, respectively. A first fluid then enters flowpath41 and a second fluid then enters flowpath51 through the respective sets of inlet and outlet ports, and through the respective fluid flow paths respectively, in counterflow operation. The first and second fluids flow in opposite directions through the respective fluid paths between the helices to cool one of the fluids by transferring heat through the helices to the other fluid.
• After insertion oftube insert100 intotube10, the outer edges of thehelices120,130 are sealed to theinner surface11 oftube10 and the inner edges of thehelices120,130 are sealed to the outer surface ofinner expansion tube110 to create fluid-tightfluid flow paths41,51. Any suitable sealing material may be employed between the helices edges andtubes10 and110.
• FIG. 5 depicts a top plan view of a portion of the helical tube insert as shown inFIG. 4A, taken along length L3. As shown inFIG. 5, in at least one embodiment of the present invention,inner expansion tube110 is capable of receiving anexpansion mandrel113 inserted therethrough. After insertion oftube insert100 intotube10,expansion mandrel113 is inserted intoinner expansion tube110 to expandtube insert100 outwardly indirection114.Tube insert100 is expanded such that the tube insert is a tight fit against theinner surface11 oftube10, as shown inFIG. 4A, in preparation for sealingtube insert100 to the inner surface of the tube to complete the assembly.
• The tube insert (helices120,130 and inner expansion tube110) and, optionally, the tube, are made of thermally conductive metal, such as aluminum or copper alloys. All parts of the heat exchanger may be made of an aluminum alloy clad with a brazing alloy, and the unit may be flux brazed in a cab (controlled atmosphere brazing) furnace, as per standard aluminum liquid-to-liquid heat exchanger manufacturing techniques. Brazing of the entire unit ensures that the edges ofhelices120,130 oftube insert100, which are in a tight fit against theinner surface11 of thetube10 and the outer surface ofinner expansion tube110, become sealed thereto, and helices ends121,131 and124,134, are sealed to endcaps14 and24, respectively, such that two distinct fluid flow paths are created and no common fluid is allowed to flow on both sides of the helices in the same direction, ensuring optimal heat transfer, as shown inFIG. 4A.
• In at least one embodiment of the present invention, projections such as turbulating dimples or ridges of various shapes may be incorporated by deformation or embossment of thehelices120,130 to provide turbulation, as shown inFIG. 6.FIG. 6 shows atube insert100′ havingturbulating dimples140 having an oval shape within the fluid flow paths created by and defined between the first122,132 andsecond sides123,133 ofhelices120,130. The projections may have alternative shapes such as circular, triangular, or other geometrical shape. The projections ordimples140 promote transfer of heat from a heated first fluid to a second cooled fluid through the helices during operation of the liquid-to-liquid heat exchanger of the present invention.
• It should be understood that the present invention as described above has been described in its basic form of a heat exchanger assembly including one heat exchanger tube with helical tube insert sealed therein. More than one heat exchanger tube with helical tube insert may be combined into a larger heat exchanger assembly (FIGS. 7-9), per design requirements, in accordance with the objects of the present invention.
• In such a configuration, a plurality of helical heat exchanger tubes are positioned such that the first fluid inlet ports of each helical heat exchanger are arranged in parallel, the second fluid inlet ports of each helical heat exchanger are arranged in parallel, the first fluid outlet ports of each helical heat exchanger are arranged in parallel and the second fluid outlet ports of each helical heat exchanger are arranged in parallel. The assembly includes inlet and outlet manifolds connecting each of the first fluid inlet and outlet ports, respectively, and each of the second fluid inlet and outlet ports, respectively. Each manifold includes a fluid port for passage of a first or second fluid, respectively, into or out of the heat exchanger assembly. The inlet and outlet manifolds are each sealed to prevent fluid mixing inside the heat exchanger assembly, and the first and second inlet and outlet manifold fluid ports may be arranged for counterflow operation whereby the first and second fluids flow in opposite directions.
• FIGS. 7-9 depict an embodiment of the present invention wherein a heat exchanger assembly comprises multiple helical heat exchangers arranged in parallel and combined into a larger assembly. As shown inFIG. 7,heat exchanger assembly1000 includes afirst inlet manifold200 having a firstfluid inlet port210 for passage of afirst fluid41 into the assembly and afirst outlet manifold300 having a first fluid outlet port310 (not shown) for passage of thefirst fluid41 out of the assembly. The assembly further includes asecond inlet manifold400 having a secondfluid inlet port410 for passage of asecond fluid51 into the assembly and asecond outlet manifold500 having a secondfluid outlet port510 for passage of thesecond fluid51 out of the assembly. The inlet and outlet manifolds are each sealed to prevent mixing of the first andsecond fluids41,51 inside the heat exchanger assembly.
• FIG. 8 depicts a cross-sectional view ofheat exchanger assembly1000, taken along section B-B ofFIG. 7. As shown inFIG. 8,heat exchanger assembly1000 includes threeheat exchanger tubes10, each with ahelical tube insert100 secured therein. Thetubes10 are positioned such that the secondfluid outlet ports52 of each heat exchanger tube are arranged in parallel. The secondfluid outlet ports52 are connected by asecond outlet manifold500.Second outlet manifold500 is sealed to prevent fluid mixing inside the assembly and includes a secondfluid outlet port510 for passage of thesecond fluid51 out of the assembly. On the opposing side of the assembly, the first fluid outlet ports42 (not shown) are also arranged in parallel and connected by afirst outlet manifold300.First outlet manifold300 is sealed to prevent fluid mixing inside the assembly and includes a firstfluid outlet port310 for passage of thefirst fluid41 out of the assembly. Any suitable sealing material may be employed to seal the respective manifolds. The number of heat exchanger tubes arranged in parallel in one assembly is shown as three, for illustrative purposes only, as an assembly including two, or more than three, heat exchanger tubes still falls under the scope of the invention.
• FIG. 9 depicts a cross-sectional view ofheat exchanger assembly1000, taken along section A-A ofFIG. 7. As shown inFIG. 9, each of the firstfluid inlet ports40 are arranged in parallel and connected byfirst inlet manifold200, and each of the secondfluid inlet ports50 are arranged in parallel and connected bysecond inlet manifold400.First inlet manifold200 has afluid inlet port210 for passage of afirst fluid41 into the assembly, andsecond inlet manifold400 has asecond inlet port410 for passage of asecond fluid51 into the assembly. As shown inFIG. 9, first and second inlet and outlet manifoldfluid ports210,310,410,510 are arranged for counterflow operation.
• Thus the present invention achieves one or more of the following advantages. The present invention provides an improved heat exchanger assembly which includes a tube with helical tube insert sealed therein, thereby creating two fluid-tight fluid flow paths of considerably increased length within the tube. The heat exchanger provides a considerable increase in fluid flow path length, and consequently an increase in heat transfer, for a given tube length, and thus provides superior heat transfer performance over that of a typical liquid-to-liquid heat exchanger. The heat exchanger allows for counterflow operation, providing optimum heat transfer performance, and makes use of standard aluminum liquid-to-liquid heat exchanger manufacturing techniques, such as inner tube expansion and cab (controlled atmosphere brazing) furnace flux brazing.
• While the present invention has been particularly described, in conjunction with a specific embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.

Claims (34)

Thus, having described the invention, what is claimed is:

1. A helical heat exchanger assembly, comprising:

a tube having first and second ends, a length, an inner diameter and a cross-section incorporating the inner diameter;

a thermally conductive tube insert having a length and a substantially similar cross-section to the cross-section of the tube, the tube insert having first and second ends and including a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends, each of the first ends offset from the other by a predetermined angle and each of the second ends offset from the other by a predetermined angle, the tube insert sealed within the tube to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices; and

a plurality of inlet and outlet fluid ports for passage of a first and second fluid into and out of the tube.

2. The heat exchanger assembly ofclaim 1 wherein the fluid ports are arranged for counterflow operation whereby the first and second fluids flow in opposite directions.

3. The heat exchanger assembly ofclaim 2 wherein at least one of the inlet or outlet fluid ports in a set of fluid ports is positioned in an opening in a wall of the tube.

4. The heat exchanger assembly ofclaim 2 wherein at least one of the inlet or outlet fluid ports in a set of fluid ports is positioned on an end of the tube.

5. The heat exchanger assembly ofclaim 1 wherein each of the tube and tube insert has a substantially circular cross-section.

6. The heat exchanger assembly ofclaim 1 wherein the first ends of the helices are offset from each other by an angle of 180 degrees.

7. The heat exchanger assembly ofclaim 1 wherein each of the helices has a predetermined pitch which is less than the tube inner diameter.

8. The heat exchanger assembly ofclaim 1 wherein the tube insert does not extend substantially beyond the tube first or second ends.

9. The heat exchanger assembly ofclaim 1 wherein the assembly includes a first end cap sealed to the tube and tube insert first ends and a second end cap sealed to the tube and tube insert second ends.

10. The heat exchanger assembly ofclaim 9 wherein the first and second end caps are flat, circular plates and are sealed flush with the ends of the tube and tube insert to prevent fluid mixing inside the heat exchanger.

11. The heat exchanger assembly ofclaim 1 wherein the tube insert includes an inner expansion tube having first and second ends, a length and a diameter less than the tube insert outer diameter, the inner expansion tube capable of receiving an expansion mandrel inserted therein to expand the tube insert into a tight fit with an inner surface of the tube, the helices extending along the length of and winding around the inner expansion tube.

12. The heat exchanger assembly ofclaim 11 wherein the assembly includes a first end cap sealed to the tube, tube insert, and inner expansion tube first ends and a second end cap sealed to the tube, tube insert, and inner expansion tube second ends.

13. The heat exchanger assembly ofclaim 12 wherein the first and second end caps are flat, circular plates and are sealed flush with the ends of the tube, tube insert, and inner expansion tube to prevent fluid mixing inside the heat exchanger.

14. The heat exchanger assembly ofclaim 1 wherein at least one of the helices includes turbulating dimples or ridges.

15. The heat exchanger assembly ofclaim 1 wherein the tube and tube insert are comprised of braze-clad aluminum.

16. The heat exchanger assembly ofclaim 15 wherein the helices and tube are brazed together to create fluid-tight first and second fluid flow paths.

17. The heat exchanger assembly ofclaim 1 wherein the assembly includes a plurality of tubes with tube inserts sealed therein, the first fluid inlet ports of each tube arranged in parallel and the second fluid inlet ports of each tube arranged in parallel, and the first fluid outlet ports of each tube arranged in parallel and the second fluid outlet ports of each tube arranged in parallel, and further including:

a first inlet manifold connecting each of the first fluid inlet ports, the first inlet manifold including a fluid inlet port for passage of a first fluid into the heat exchanger assembly;

a first outlet manifold connecting each of the first fluid outlet ports, the first outlet manifold including a fluid outlet port for passage of a first fluid out of the heat exchanger assembly;

a second inlet manifold connecting each of the second fluid inlet ports, the second inlet manifold including a fluid inlet port for passage of a second fluid into the heat exchanger assembly; and

a second outlet manifold connecting each of the second fluid outlet ports, the second outlet manifold including a fluid outlet port for passage of a second fluid out of the heat exchanger assembly,

wherein the inlet and outlet manifolds are each sealed to prevent fluid mixing inside the heat exchanger assembly.

18. The heat exchanger assembly ofclaim 17 wherein the first and second inlet and outlet manifold fluid ports are arranged for counterflow operation whereby the first and second fluids flow in opposite directions.

19. A method of assembling a heat exchanger, comprising the steps of:

providing a tube having first and second ends, a length, an inner diameter and a cross-section incorporating the inner diameter;

providing a thermally conductive tube insert having first and second ends, a length and a substantially similar cross-section to the cross-section of the tube, the tube insert including a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends, each of the first ends offset from the other by a predetermined angle and each of the second ends offset from the other by a predetermined angle;

inserting the tube insert within the tube and sealing the tube insert therein to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices; and

providing a plurality of inlet and outlet fluid ports for passage of a first and second fluid into and out of the tube.

20. The method ofclaim 19 wherein the fluid ports are arranged for counterflow operation whereby the first and second fluids flow in opposite directions.

21. The method ofclaim 19 wherein the tube insert is inserted within the tube by automation.

22. The method ofclaim 19 wherein each of the tube and tube insert has a substantially circular cross-section.

23. The method ofclaim 19 wherein the first ends of the helices are offset from each other by an angle of 180 degrees.

24. The method ofclaim 19 wherein each of the helices has a predetermined pitch which is less than the tube inner diameter.

25. The method ofclaim 19 wherein the tube insert does not extend substantially beyond the tube first or second ends.

26. The method ofclaim 19 wherein at least one of the helices includes turbulating dimples or ridges.

27. The method ofclaim 19 further including the steps of:

sealing a second end cap to the tube and tube insert second ends; and

sealing a first end cap to the tube and tube insert first ends.

28. The method ofclaim 27 wherein the first and second end caps are flat, circular plates and are sealed flush with the ends of the tube and tube insert to prevent fluid mixing inside the heat exchanger.

29. The method ofclaim 19 wherein the tube insert includes an inner expansion tube having first and second ends, a length and a diameter less than the tube insert outer diameter, the inner expansion tube capable of receiving an expansion mandrel inserted therein to expand the tube insert into a tight fit with an inner surface of the tube, the helices extending along the length of and winding around the inner expansion tube, and further including the step of:

inserting the expansion mandrel into the inner expansion tube and expanding the tube insert until the tube insert is a tight fit against an inner surface of the tube.

30. The method ofclaim 29 further including the steps of:

sealing a second end cap to the tube, tube insert, and inner expansion tube second ends; and

sealing a first end cap to the tube, tube insert, and inner expansion tube first ends.

31. The method ofclaim 30 wherein the first and second end caps are flat, circular plates and are sealed flush with the ends of the tube, tube insert, and inner expansion tube to prevent fluid mixing inside the heat exchanger.

32. The method ofclaim 19 wherein the tube and tube insert are comprised of braze-clad aluminum, and further including the step of:

brazing the heat exchanger in a furnace to create fluid-tight first and second fluid flow paths.

33. A method of operating a heat exchanger assembly, comprising:

providing a heat exchanger having a tube with first and second ends, a length, an inner diameter and a cross-section incorporating the inner diameter; a thermally conductive tube insert having a length and a substantially similar cross-section to the cross-section of the tube, the tube insert including a pair of helices extending along the length of the tube insert, the helices having first and second sides offset from each other by a predetermined distance along the length of the tube insert and first and second ends, each of the first ends offset from the other by a predetermined angle and each of the second ends offset from the other by a predetermined angle, the tube insert sealed within the tube to form a first fluid flow path and a second fluid flow path, the first fluid flow path defined between the first sides of the helices and the second fluid path defined between the second sides of the helices; and a plurality of inlet and outlet fluid ports for passage of a first and second fluid into and out of the tube;

connecting inlet and outlet fluid lines for a first fluid to a first set of inlet and outlet ports;

connecting inlet and outlet fluid lines for a second fluid to a second set of inlet and outlet ports; and

flowing the first and second fluids through the first and second sets of inlet and outlet ports, respectively, to cool one of the fluids.

34. The method ofclaim 33 wherein the first and second sets of inlet and outlet fluid ports are arranged for counterflow operation whereby the first and second fluids flow in opposite directions through the first and second fluid paths between the helices.

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