Field of Invention

[0001] The present disclosure relates to heat exchangers, particularly to ones based on metallic ribbons having multiple passages.

Background

[0002] Heat exchangers are used in domestic and industrial applications. In some applications, such as a Vuilleumier heat pump where the space is limited and the application is demanding, new designs using modern manufacturing techniques and newly available materials may be used to increase the performance to meet design goals.

Summary

[0003] A method to manufacture a heat exchanger is disclosed that includes: cutting a section of a metallic ribbon of a predetermined length, the metallic ribbon having multiple parallel passages, winding the metallic ribbon section into a spiral of a predetermined number of turns, and providing a gap of a predetermined thickness between adjacent turns of the spiraled metallic ribbon. The method may further include providing a fluidic inlet to the plurality of passages at a first angular position of the spiraled metallic ribbon and providing a fluidic outlet to the plurality of passages at a second angular position of the spiraled metallic ribbon. The method may also include sealing the plurality of passages at a first end of the metallic ribbon and sealing the plurality of passages at a second end of the metallic ribbon.

[0004] The method includes inserting one each of a first plurality of spacers between adjacent turns of the spiraled metallic ribbon at the first angular position on the spiraled metallic ribbon and inserting one each of a second plurality of spacers between adjacent turns of the spiraled metallic ribbon at the second angular position on the spiraled metallic ribbon. In some embodiments, the first and second angular positions are diametrically opposed.

[0005] In one embodiment, the first and second spacers are tines of first and second combs. In an alternative embodiment, first spacers and second spacers are flat sheets clad with a brazing material on each side. [0006] In some embodiments, the outer end of the spiraled metallic ribbon relative is rotated to an inner end of the spiraled metallic ribbon to increase gaps between adjacent turns of the spiraled metallic ribbon to facilitate installation of the first and second spacers.

[0007] The method includes: fabricating an outer ring having an outer-ring pocket for an outer end of the spiraled metallic ribbon, fabricating an inner ring having an inner-ring pocket for an inner end of the spiraled metallic ribbon, rotating an outer end of the spiraled metallic ribbon relative to an inner end of the spiraled metallic ribbon to reduce a gap between adjacent turns of the spiraled metallic ribbon, and inserting the spiraled metallic ribbon between the outer ring and the inner ring.

[0008] The method may further include: heating the spiraled metallic ribbon, the outer ring, and the inner ring to braze the first and second spacers to the spiraled metallic ribbon. The spiraled metallic ribbon, the outer ring, and the inner ring are cooled to solidify the braze material.

[0009] The method includes machining the coolant inlet and the coolant outlet through the outer ring and the spiraled metallic ribbon. The coolant inlet is

substantially along a first radius of the outer ring, the coolant outlet is substantially along a second radius of the outer ring, and the first radius is angularly displaced from the second radius.

[0010] The passages in the metallic ribbon fluidly couple the coolant inlet with the coolant outlet.

[0011] In some embodiments, the first and second spacers comprise tines of first and second combs that are coated in a braze material.

[0012] In some embodiments, the first and second spacers each comprise a plurality of metallic sheets clad with a braze material. The sheets are shaped as an oval, a circle, a annulus, an annular oval, a polygon, a polygon with rounded corners, or a polygon with a hole defined therein.

[0013] Also disclosed is a spiraled metallic ribbon having a plurality of parallel passages. The spiraled metallic ribbon has gaps between adjacent turns. A first plurality of spacers is placed into gaps between adjacent turns of the spiraled metallic ribbon at a first angular position on the spiraled metallic ribbon. A second plurality of spacers placed into gaps between adjacent turns of the spiraled metallic ribbon at a second angular position on the spiraled metallic ribbon. The first angular position is displaced from the second angular position. In some embodiments, the first angular position is diametrically opposed from the second angular position.

[0014] The heat exchanger has an inner ring inserted into the spiraled metallic ribbon and an outer ring into which the spiraled metallic ribbon is inserted. The first and second pluralities of spacers have a brazing material on outer surfaces. The inner ring, outer ring, spiraled metallic ribbon, and spacers are heated to a temperature at which the brazing material melts.

[0015] The heat exchanger has a coolant inlet machined radially inward through the outer ring and the spiraled metallic ribbon and a coolant outlet machined radially inward through the outer ring and the spiraled metallic ribbon. The coolant inlet and coolant outlet are substantially diametrically opposed. Passages in the spiraled metallic ribbon fluidly couple with the coolant inlet and the coolant outlet.

[0016] The first and second pluralities of spacers are plates clad with a brazing material.

[0017] In some embodiments, the spacers are slightly curved to substantially the curvature of the gap into which it is inserted.

[0018] In some embodiments, the plates have a hole in the center.

[0019] In some embodiments, the first plurality of spacers are tines of first and second combs and the second plurality of spacers are tines of third and fourth combs. Third and fourth pluralities of spacers are inserted into gaps between adjacent turns of the spiraled metallic ribbon. The third plurality of spacers are tines of fifth and sixth combs. The fourth plurality of spacers comprise tines of seventh and eighth combs. The first plurality of spacers is proximate the second pluralities of spacers; the third plurality of spacers is proximate the fourth plurality of spacers. A coolant inlet is machined radially inward through the outer ring and the spiraled metallic ribbon. The coolant inlet located between the first and second pluralities of spacers. A coolant outlet is machined radially inward through the outer ring and the spiraled metallic ribbon. The coolant outlet located between the third and fourth pluralities of spacers.

[0020] The coolant inlet and coolant outlet are substantially diametrically opposed.

[0021] The passages in the spiraled metallic ribbon fluidly couple the coolant inlet with the coolant outlet. [0022] An advantage of such a heat exchanger is that it can be compactly fitted into an annular space. Furthermore, it is constructed of available components that allow a complex piece of hardware to be constructed at reasonable cost. Brief Description of the Drawings

[0023] Figure 1 is an exploded view of a heat exchanger assembly according to an embodiment of the present disclosure;

[0024] Figure 2 is a cross sectional view of a portion of a metallic ribbon with passages formed therein;

[0025] Figures 3 and 5 are portions of the heat exchanger assembly of Figure 1 at different stages of assembly;

[0026] Figure 4 is an end view of a spacer;

[0027] Figure 6 shows the heat exchanger assembly of Figure 1 as assembled;

[0028] Figures 7 and 8 show comb spacers that are inserted between turns of a spiraled metallic ribbon;

[0029] Figure 9 shows a spiraled metallic ribbon with comb spacers inserted;

[0030] Figure 10 shows the spiraled metallic ribbon of Figure 9 with inlet and outlet holes and indicating flow directions;

[0031] Figure 11 shows a process by which the heat exchanger assembly of Figures 1, 2, 3, 5, and 6 may be manufactured; and

[0032] Figures 12-14 show heat exchangers according to embodiments of the disclosure that have diverters inserted into an inlet hole.

Detailed Description

[0033] As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations whether or not explicitly described or illustrated.

[0034] An exploded view of a heat exchanger assembly is shown in Figure 1.

Heat exchanger assembly 10 may be part of a Vuilleumier heat pump or other thermodynamic devices in which an annular-shaped heat exchanger is desirable. The heat exchanger portion is contained between an outer ring 12 and an inner ring 14. A metallic ribbon that has a plurality of passages therein is curved to form a spiraled metallic ribbon 16 that has inner end 20 and outer end 18. Spiraled metallic ribbon 16 is wound such that there is a gap between adjacent turns for a fluid to flow through the gaps. Thin spacers 30 are used to maintain the desired gap distance between adjacent turns. A first portion of spacers 30 is inserted between adjacent turns of spiraled metallic ribbon 16 at a first angular position and a second portion of spacers 30 is inserted between adjacent winds of spiraled metallic ribbon 16 at a second angular position. In some embodiments, the first and second angular positions are diametrically opposed. One of spacers 30 is placed between adjacent turns, at each of the angular positions. Spacers 30 can be annuli, circular disks, oval disks, or polygons. Spiraled metallic ribbon 16 is inserted between outer and inner rings 12 and 14 after spacers 30 have been inserted. In some embodiments, spacers 30 can be slightly curved so as to match the curvature of spiraled metallic ribbon 16.

[0035] A portion of a cross section of a metallic ribbon 36 similar to that used to make spiraled metallic ribbon 16 is shown in Figure 2. Metallic ribbon 36 has a plurality of passages 40 that extend through ribbon 16 in a parallel fashion.

[0036] A heat exchanger typically has two fluids that flow proximate each other, although not in fluidic communication, for energy transfer. Referring back to Figure 1, a first fluid flows between gaps in spiraled metallic ribbon 16 as shown by arrows 21. In a Vuilleumier heat pump application, a working fluid, such as helium, shuttles back and forth through the gaps in spiraled metallic ribbon 16. In other applications, a fluid moves in one direction only. A second fluid moves through passages within spiraled metallic ribbon 16, substantially moving in a plane defined by outer ring (i.e., a plane perpendicular to the flow direction of the first fluid as indicated by arrows 21. The second fluid is supplied to outer ring 12 through a fitting (not shown) that couples to an inlet boss 26. The second fluid exits via inlet boss 27. Later figures illustrate the fluidic communication between bosses 26 and 27 with passages within spiraled metallic ribbon 16.

[0037] In Figure 3, a portion of heat exchanger assembly 10 is shown. Because spiraled metallic ring 16 has ends 18 and 20, it is not completely cylindrical. A pocket 22 is provided in outer ring 12 to accommodate end 18 and a pocket 24 is provided in inner ring 14 to accommodate end 20. Spacers 30 are shown between adjacent winds of spiraled metallic ribbon 16 in a portion of the section shown in Figure 3. Gaps 31 are visible in regions in which there are no such spacers.

[0038] In Figure 4, an end view of a spacer 30 is shown. Spacer 30 has a base material 33 that has a braze material cladding 33 on each side of base material 33. Heat exchanger assembly 10 is heated to a temperature above which the braze material cladding 33 flows. Upon cooling, spacers 30 solidify with adjacent turns of spiraled metallic ribbon 16.

[0039] In Figure 5, a portion of heat exchanger assembly 10 is shown in cross section. Wall 52 is made up of sections of the turns of spiraled metallic ribbon 16 and spacers 30. The two elements (16 and 30) are not indistinguishable after the braze material has flowed so that wall 52 is formed. A hole 50 is machined radially through outer ring 12 toward inner ring 14. Hole 52 is specifically machined to be centrally located with respect to spacers 30 (spacers 30 are not individually visible in Figure 5) so that wall 52 is substantially the same size on either side of hole 50. Hole 50 breaks through spiraled metallic ribbon 16 so that hole 50 is in fluidic communication with passages 38. Some of passages 38 appear as circles in Figure 5. Hole 50 intersects some of passages 38 at an angle so that the openings appear as ovals. A boss 26 is provided on outer ring 12 for attaching fittings (not shown) to bring a fluid into or out of heat exchanger assembly 10. Hole 50 serves as a fluidic couple between boss 26 and passages 38.

[0040] Heat exchanger assembly 10 is shown assembled in Figure 6. Spiraled metallic ribbon 16 is inserted between outer ring 12 and inner ring 14. Spacers 30 are inserted between turns. Bosses 26 are formed on the outside of outer ring 12. Holes 50 are machined through boss 26, outer ring 12, spacers 30, and through spiraled metallic ribbon 16. Fluid flows through heat exchanger assembly 10 as shown by arrows 28.

[0041] An alternative to spacers 30 are comb-like structures, as show in Figure 7.

An upper comb 60 having a plurality of tines and a lower comb 62 having a plurality of tines are slid into the gaps between turns 64 of the metallic ribbon. In Figure 7, a slice of a spiraled metallic ribbon with five turns is shown. Each of combs 60 and 62 have a tine spaced to slide in every other gap in the spiraled metallic ribbon. In Figure 8, combs 60 and 62 fully slid into the gaps between turns 64 is shown.

[0042] In Figure 9, a plan view of a spiraled metallic ribbon 164 is shown. Upper combs 160 are shown on one angular position. The corresponding lower combs are not visible in this view. At the angular position near where the ends 170 and 172 of the metallic ribbon is located, upper combs 161 are provided. Tines of the combs are coated with a brazing cladding or with a brazing paste. When heated, the brazing material flows to fill spaces and causes the tines to form a solid piece with spiraled metallic ribbon 164. Combs 160 are diametrically opposed from combs 161.

[0043] After the heating process, an opening is formed openings are formed, as illustrated in Figure 10. A hole is machined between combs 160 and a hole is machined between combs 161 to expose passages in spiraled metallic ribbon 164. Coolant can flow in at 200 and then into passages in spiraled metallic ribbon, as shown by arrow 202. The flow continues through all of the passages in the directions indicated by arrows 210 and 212. Flow of coolant exits through passages exposed to the hole between combs 161, as shown by arrows 222 and 220. Flow does not go through opening 204 or opening 224 but instead through the passages in spiraled metallic ribbon 164 because there is an inner ring (not shown in Figure 10) that blocks 204 and 224. A central axis 230 of spiraled metallic ribbon 164 extends in the plane shown in Figure 10. Flow through gaps 228 between adjacent turns travels roughly parallel to central axis 230. In some applications such as the Vuilleumier heat pump, the flow is pumped through in both directions throughout the cycle. In other applications, flow is in a single direction.

[0044] Referring back to Figures 7 and 8, combs 60 and 62 have connector portions 63 that hold tines 61 in position. Connector portions 63 stand proud of the spiraled metallic ribbon upon assembly. After the brazing process is completed to cause tines 61 to be brazed to portions of the turns of the spiraled metallic ribbon, connector portions 63 can be machine down to cause them to extend beyond the spiraled metallic ribbon less.

[0045] A process by which the heat exchanger can be assembled is shown in

Figure 11. A metallic ribbon that has a plurality of plural passages extending through it is extruded in block 300. A predetermined length of the metallic ribbon is cut in block 302. The metallic ribbon is wound into a spiral in block 304. In block 306, the passages in the metallic ribbon are sealed off. The ends of the spiraled metallic ribbon are rotated with respect to each other so that the gap distance between adjacent turns is increased in block 308. Spacers are inserted between adjacent turns of the metallic ribbon at first and second angular positions in block 310 and 312, respectively. In block 316, the ends of the spiraled metallic ribbon are rotated with respect to each other to decrease the gap distance between adjacent turns in block 316 to facilitate inserting the spiraled metallic ribbon between inner and outer rings in block 318. The spacers are clad with a braze material or coated with a braze paste. In block 320, the assembly (inner and outer rings, spiraled metallic ribbon, and spacers) are heated to a

temperature above which the brazing material melts or begins to flow. Or, in the case of a braze paste, the metallic particles in the paste melt and the liquid vaporizes. When the assembly is cooled down, a bond is formed between portions of the turns of the spiraled metallic ribbon that are adjacent the spacers. In block 322, two holes are machined through the outer ring and into the spiraled metallic ribbon. The holes do not extend into the inner ring. The two holes extend radially toward the center of the assembly and are diametrically opposed to each other. The processes described in Figure 11 are non- limiting in terms of order and some processes may be eliminated in some embodiments.

[0046] As illustrated in Figures 6 and 10, flow enters the heat exchanger at one diametric position (an inlet hole), turns either toward the right or left to flow along one half of the ring, and the exits via an outlet hole that is diametrically opposed from the inlet hole. It is desirable to have the flow distributed evenly to provide suitable heat exchanger effectiveness. To this end, a portion of a heat exchanger 400 is shown in Figure 12 that has an inlet hole 402 with a vertical diverter 404. Vertical diverter 404 is press fit or brazed to keep it in place. Alternatively, in Figure 13, a horizontal diverter 414 is inserted in inlet hole 412 of heat exchanger 410. Some of passages 416 are visible in Figure 13. Heat exchanger 400 also has passages, yet these are not visible due to the angle of the illustration causing diverter 404 to occlude the passages. In Figure 14, a diverter 424 has a horizontal and a vertical section is placed in inlet hole 422 in heat exchanger 420. Diverters 404 and 414 are press fit or brazed in place so that they do no shift. Diverter 424 may also be press fit or brazed. Due to diverter 424 having both vertical and horizontal sections, diverter 424 may be slip fit into inlet hole 422. Brazing is a non-limiting way of affixing the diverter to the heat exchanger. Any suitable coupling technique can be used. Figures 12-14 show diverters 404, 414, and 424 integral with heat exchangers 400, 410, and 420, respectively. This is indicating that a technique such as brazing in which the metals pieces become continuous. However, this is a non-limiting feature in the drawings. An interface between diverters and their respective heat exchanger would be visible in embodiments using slip fit or interference fit.

[0047] While the best mode has been described in detail with respect to particular embodiments, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and

implementation. These attributes include, but are not limited to: cost, efficiency, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described herein that are characterized as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.