Heater Exchanger for Water Heaters

Abstract

An improved heat exchanger for a water heater is provided. The heat exchanger includes a plurality of dimples are indented into the surface of the flue tubes used in the heat exchanger. The arrangement, size, and shape of the dimples are optimized such that the thermal efficiency of the heat exchanger is maximized while still maintaining the structural integrity of the flue tubes. Additionally, the heat exchanger includes diverters that directly connect the second and third-pass flue tubes such that the flow of hot gas from the combustions system through the flue tubes occurs entirely under the top pan of the water heater.

Claims

1. A water heater comprising: a combustion system; a water tank; a top cover assembly having a top surface; and a multi-pass heat exchanger positioned in the water tank and underneath the top cover assembly, wherein the multi-pass heat exchanger comprises flue tubes arranged such that hot gas received from the combustion system flows through the multi-pass heat exchanger without flowing onto or above the top cover assembly, and wherein the flue tubes include a plurality of dimples positioned along a length of the flue tubes.

2. The water heater of claim 1, wherein the flue tubes are a carbon steel material.

3. The water heater of claim 1, wherein the plurality of dimples include a first dimple positioned across from a second simple, and a third dimple and a fourth dimple staggered from the first dimple and second dimple.

4. The water heater of claim 3, wherein a spacing between the first dimple and the third dimple is within a range of 2.5 inches to 3 inches and a depth of the plurality of dimples is within a range of 0.75 inches to 1 inch.

5. The water heater of claim 1, wherein the flue tubes include a first-pass flue tube, a first second-pass flue tube, and a first third-pass flue tube, wherein the first-pass flue tube is configured to pass hot gas from the combustion system to the first second-pass flue tube, and wherein the first second-pass flue tube is configured to pass the hot gas to the first third-pass flue tube.

6. The water heater of claim 5, wherein the first-pass flue tube is centrally disposed within the water tank, wherein the first second-pass flue tube is radially disposed from the first-pass flue tube, and wherein the first third-pass flue tube is radially disposed from the first-pass flue tube.

7. The water heater of claim 5, further comprising: a second third-pass flue tube connected to the first second-pass flue tube.

8. The water heater of claim 7, further comprising: a second second-pass flue tube and a third second-pass flue tube; a third third-pass flue tube and a fourth third-pass flue tube connected to the second second-pass flue tube; and a fifth third-pass flue tube and a sixth third-pass flue tube connected to the third second-pass flue tube.

9. The water heater of claim 8, wherein the third third-pass flue tube and the fourth third-pass flue tube are connected to the second second-pass flue tube underneath the top cover assembly, and the fifth third-pass flue tube and the sixth third-pass flue tube are also connected to the third second-pass flue tube underneath the top cover assembly.

10. The water heater of claim 8, further comprising: a fourth second-pass flue tube; and a seventh third-pass flue tube and an eighth third-pass flue tube connected to the fourth second-pass flue tube.

11. A heat exchanger comprising: a first-pass flue tube configured to receive hot gas from a combustion system of a water heater; a first second-pass flue tube connected to the first-pass flue tube and configured to receive the hot gas from the first-pass flue tube; and a first third-pass flue tube connected to the first second-pass flue tube and configured to receive the hot gas from the first second-pass flue tube, wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube are positioned in a water tank of the water heater and underneath a top cover assembly of the water heater, and wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube include a plurality of dimples.

12. The heat exchanger of claim 11, wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube are a carbon steel material.

13. The heat exchanger of claim 11, wherein the plurality of dimples include a first dimple positioned across from a second simple, and a third dimple and a fourth dimple staggered from the first dimple and second dimple.

14. The heat exchanger of claim 13, wherein a spacing between the first dimple and the third dimple is within a range of 2.5 inches to 3 inches and a depth of the plurality of dimples is within a range of 0.75 inches to 1 inch.

15. The heat exchanger of claim 11, wherein the first-pass flue tube is centrally disposed within the water tank, wherein the first second-pass flue tube is radially disposed from the first-pass flue tube, and wherein the first third-pass flue tube is radially disposed from the first-pass flue tube and is adjacent to the first second-pass flue tube.

16. The heat exchanger of claim 11, further comprising: a second third-pass flue tube also connected to the first second-pass flue tube.

17. The heat exchanger of claim 16, further comprising: a second second-pass flue tube and a third second-pass flue tube; a third third-pass flue tube and a fourth third-pass flue tube connected to the second second-pass flue tube; and a fifth third-pass flue tube and a sixth third-pass flue tube connected to the third second-pass flue tube.

18. The heat exchanger of claim 17, wherein the third third-pass flue tube and the fourth third-pass flue tube are connected to the second second-pass flue tube underneath the top cover assembly, and the fifth third-pass flue tube and the sixth third-pass flue tube are also connected to the third second-pass flue tube underneath the top cover assembly.

19. The heat exchanger of claim 17, further comprising: a fourth second-pass flue tube; and a seventh third-pass flue tube and an eighth third-pass flue tube connected to the fourth second-pass flue tube.

20. A heating appliance comprising: a combustion system; a water tank; a top cover assembly having a top surface, wherein the combustion system is disposed on the top surface; and a multi-pass heat exchanger comprising: a first-pass flue tube configured to receive hot gas from a combustion system; a first second-pass flue tube connected to the first-pass flue tube and configured to receive the hot gas from the first-pass flue tube; and a first third-pass flue tube connected to the first second-pass flue tube and configured to receive the hot gas from the first second-pass flue tube, wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube are positioned in a water tank of the heating appliance and underneath the top cover assembly of the heating appliance, and wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube include a plurality of dimples.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The detailed description is set forth with reference to the accompanying drawings. In some instances, the use of the same reference numerals may indicate similar or identical items. Various embodiments may utilize elements and/or components other than those illustrated in the drawings, and some elements and/or components may not be present in various embodiments. Throughout this disclosure, depending on the context, singular and plural terminology may be used interchangeably.

[0005] FIG. 1 illustrates a water heater, in accordance with one or more embodiments of the disclosure.

[0006] FIG. 2 illustrates a top-down view of a cross-section of a heat exchanger provided inside of a water tank, in accordance with one or more embodiments of the disclosure.

[0007] FIG. 3A illustrates a perspective view of a heat exchanger inside a water heater, in accordance with one or more embodiments of the disclosure.

[0008] FIG. 3B illustrates a close-up view of a dimpled tube of the heater exchanger of FIG. 3A, in accordance with one or more embodiments of the disclosure.

[0009] FIGS. 4A-4C illustrate side views of various heat exchanger configurations, in accordance with one or more embodiments of the disclosure.

[0010] FIGS. 5A-5C illustrate top-down views of the various heat exchanger configurations of FIGS. 4A-4C, in accordance with one or more embodiments of the disclosure.

[0011] FIG. 6 illustrates a diverter of a heat exchanger, in accordance with one or more embodiments of the disclosure.

[0012] FIG. 7 illustrates a perspective view of another diverter of a heat exchanger, in accordance with one or more embodiments of the disclosure.

[0013] FIG. 8 illustrates a close-up side view of the diverter of FIG. 7, in accordance with one or more embodiments of the disclosure.

[0014] FIG. 9A illustrates a perspective view of another diverter of a heat exchanger, in accordance with one or more embodiments of the disclosure.

[0015] FIG. 9B illustrates a close-up side view of the diverter of FIG. 9A, in accordance with one or more embodiments of the disclosure.

[0016] FIG. 10A illustrates a perspective view of another diverter of a heat exchanger, in accordance with one or more embodiments of the disclosure.

[0017] FIG. 10B illustrates a close-up side view of the diverter of FIG. 10A, in accordance with one or more embodiments of the disclosure.

[0018] FIGS. 11A-11B illustrate close-up views of dimples of a heat exchanger, in accordance with one or more embodiments of the disclosure.

[0019] FIGS. 11C-11D illustrate cross-section views of the dimples of FIGS. 11A-11B, in accordance with one or more embodiments of the disclosure.

[0020] FIG. 12A illustrates a side view of a tool used to produce dimples in a flue tube, in accordance with one or more embodiments of the disclosure.

[0021] FIG. 12B illustrates a perspective view of a tool used to produce dimples in a flue tube, in accordance with one or more embodiments of the disclosure.

DETAILED DESCRIPTION

[0022] Disclosed herein is an improved heat exchanger for water heaters. The water heater may include a water tank that may be any suitable size, shape, or configuration (for example, generally cylindrical in some instances). The heat exchanger may be provided within the water tank and is used to heat the water stored within the water tank. That is, a combustion system of the water heat produces hot gases that are directed into flue tubes of the heat exchanger. As the hot gases traverse the flue tubes of the heat exchanger within the water tank, thermal transfer occurs between the flue tubes and the water in the water tank to heat the water in the water tank. The hot water stored in the water tank may then be routed for usage for various residential and/or commercial purposes, such as water for a shower, a sink, etc.

[0023] The improved heat exchanger is a multi-pass heat exchanger that includes first, second, and third-pass flue tubes, which are provided in the water tank of the water heater. The first-pass flue tube is connected to the combustion system of the water heater such that hot gas produced by the combustion system flows into the first-pass flue tube. Multiple second-pass flue tubes are connected to the first-pass flue tube and multiple third-pass flue tubes are connected to the second-pass flue tubes. Accordingly, the hot gas that passes through the first-pass flue tube subsequently passes from the first-pass flue tube into the second-pass flue tubes, and then finally from the second-pass flue tubes into the third-pass flue tubes. Thus, the hot gas may be used to heat the water in the water tank while being reduced to a threshold temperature after passing through all three sets of tubes.

[0024] The first, second, and third-pass flue tubes are provided with dimples (for example, as shown in FIG. 3B). In some implementations, dimples may be excluded from one or more of the first, second, or third-pass flue tubes. The dimples may be indentations that are formed into the surface of a flue tube such that the surface is pressed to a certain depth within an internal cavity of the flue tube. In embodiments, the dimples may be provided in a staggered arrangement along the length of the flue tubes. For example, a first dimple and a second dimple may be provided across from one another (e.g., radially offset by 180 degrees) and a third dimple and a fourth dimple may likewise be provided across from one another and staggered from the first dimple and second dimple (e.g., longitudinally offset and radially offset by 90 degrees from the first and second dimple, respectively). This pattern may be repeated down the length of a given flue tube. However, other dimple arrangements are also possible. The use of the multi-pass flue tubes and the dimples increases thermal efficiency in the water tank of the water heater.

[0025] In embodiments, the flue tubes of the heat exchanger are made from carbon steel. When using flue tubes made from carbon steel, the specific arrangement, size, and shape of the dimples is impacted because carbon steel is a more brittle material than, for example, stainless steel. Accordingly, even if existing heat exchangers use flue tubes that include dimples, the arrangement, size, and shape of the dimples in these existing heat exchangers cannot simply be applied to the heat exchanger made using a carbon steel material. Any reference to carbon steel herein is merely exemplary and the same may be applicable to any other type of material for which structural integrity is a consideration (for example, materials that may experience diminished structural integrity or may break depending on the arrangement, size, and shapes of the dimples).

[0026] The specific arrangement, size, and shape of the dimples described herein are not only configured to maintain the structural integrity of the flue tubes but simultaneously serve to optimize the thermal performance (for example, the heat exchanger described herein is optimized to provide 95% thermal efficiency or more) of the water heater. Other existing heat exchangers may be used to attempt to improve thermal efficiency using other types of structures (for example, baffles provided in the internal cavity of the flue tubes), however, these types of structures may involve a more difficult manufacturing process and added cost. In contrast, producing a heat exchanger using dimples rather than internal baffles reduces the manufacturing difficulty of the heat exchanger. The dimples provided on the second and third-pass flue tubes also reduce the pressure drop within the heat exchanger without compensating with less efficient heat dissipation. The third-pass flue tubes are also configured to provide condensation with the flue gas reaching below a threshold temperature to maximize the heat transfer from the heat exchanger into the water in the water tank.

[0027] In embodiments, the dimples may be produced such that gaps are provided between opposing dimples. This is also advantageous because it provides spacing for a porcelain or enamel coating (or other type of coating) to be applied to the flue tubes, whereas if opposing dimples were to be touching, then there may not exist sufficient space for the coating to be applied to the flue tubes.

[0028] Additionally, the improved heat exchanger described herein uses an improved diverter design to direct hot gas from the second-pass flue tubes to the third-pass flue tubes without requiring a separate diverter component provided on top of the top pan of the water heater. That is, the third-pass flue tubes are connected directly to the second-pass flue tubes such that the hot gas flows directly from the second-pass flue tubes to the third-pass flue tubes. For example, the diverters may be T-shaped diverters (shown in FIG. 10B), however, other diverter configurations may also be possible.

[0029] While reference is specifically made herein to heat exchangers provided in water heaters, this is not intended to be limiting and the heat exchangers may also be provided in other types of heating appliances that use heat exchangers.

[0030] Turning to the figures, FIG. 1 illustrates a perspective view of a water heater 100 that includes a water tank 102, a top cover assembly 104, and a bottom assembly 106. The water heater 100 also includes a combustion system 108 at the top end of the water heater 100. The combustion system 108 may include a down-fired burner, where hot gas flows downward into a multi-pass heat exchanger (shown in further detail in FIGS. 2-12) disposed in the water tank 102. The water heater 100 also includes a water inlet 112 that may be disposed, for example, closer to the bottom end of the water tank 102. The water tank 102 also includes a top water outlet 110 through the top cover assembly 104. While specific locations for the water inlet 112 and top water outlet 110 are described, any location of the water inlet 112 and water outlet 110 are contemplated (e.g., sidewall inlet and outlet, etc.).

[0031] During the operation of the water heater 100, unheated water enters the water tank 102 through the water inlet 112, and gas is burned by the combustion system 108. The unheated water gets heated inside the water tank 102 by hot combustion gas (e.g., exhaust from the combustion system) flowing through the multi-pass heat exchanger. The resulting heated water exits the water tank 102 through the top water outlet 110 in the top cover assembly 104. The hot gas that flows through the multi-pass heat exchanger may exit the water tank through an exhaust outlet in the bottom assembly 106 to a flue (not shown).

[0032] The water heater 100 provides a top water outlet location along with the high efficiency of a multi-pass heat exchanger. By providing the top water outlet 110, the water heater 100 provides a fuel-fired water heater with a top water outlet location that is preferable in some installations.

[0033] FIG. 2 illustrates a top-down view of the inside of a water tank 201 of a water heater 200 (which may be similar to water heater 100 or any other water tank described herein). Specifically, FIG. 2 illustrates an exemplary multi-pass heat exchanger. The exemplary multi-pass heat exchanger 202 includes a first-pass flue tube 204, second-pass flue tubes 206, 208, 210, and 212, and third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240. The hot gas in the first-pass flue tube 204 is provided by the combustion system (which may be the same as, or similar to, combustion system 108), which can be a down-fired system, as more clearly illustrated in FIG. 1. Although the multi-pass heat exchanger 202 shown in FIG. 2 includes a single first-pass flue tube, four second-pass flue tubes, and fourteen third-pass flue tubes, this configuration is illustrated for exemplary purposes and other configurations are also possible (further non-limiting examples are shown in FIGS. 4A-4C and 5A-5C, for example). The below description of the size, shape, and arrangement of the various flue tubes that form the multi-pass heat exchanger 202 is not intended to be limiting and may also vary.

[0034] The multi-pass heat exchanger 202 provides for greater transference of heat over existing heat exchangers at higher inputs based on a larger surface area and increased airflow to allow the higher rate inputs. The multi-pass heat exchanger 202 shown in FIG. 2 may be configured to allow for effective heat transfer in a larger capacity water heater, such as a 120 gallon capacity water heater, for example. However, the multi-pass heat exchanger 202 may also be used in water heaters of other capacities as well. The multi-pass heat exchanger 202 may be made from a carbon steel material that is then porcelain or enamel coated but may also be made from stainless steel and/or any other type of material.

[0035] In embodiments, the multi-pass heat exchanger 202 utilizes a down fire combustion system (not shown in the figure), such as combustion system 508 (or any other combustion system described herein), mounted to a top portion 243 of the multi-pass heat exchanger 202. The combustion system is coupled to the first-pass flue tube 204 such that the heat produced by the combustion system is expelled downwards into the first-pass flue tube 204. The first-pass flue tube 204 may include a 6 diameter wedge portion connected to an 8 diameter inch expansion portion, which may extend down the length of the first-pass flue tube 204. These dimensions are merely exemplary and the first-pass flue tube 204 may also be any other size as well.

[0036] The first-pass flue tube 204 may also be supported by a support pipe, which may be welded to the heat exchanger 202. The support pipe may not necessarily include an aperture, but rather may merely serve as a mechanism to support the first-pass flue tube 204 of the multi-pass heat exchanger 202. In some instances, the support pipe may not be included and the first-pass flue tube 204 may be supported within the multi-pass heat exchanger 202 in any other suitable manner.

[0037] The heat produced by the combustion system travels down the first-pass flue tube 204 to the second-pass flue tubes 206, 208, 210, and 212. The heat then travels up the second-pass flue tubes 206, 208, 210, and 212, and into the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 via the diverter (for example, the diverter shown in FIG. 10B, and/or any other diverter described herein) at the top portion 243 of the multi-pass heat exchanger 202. Finally, the heat travels down the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 and into a collector (not shown in the figure) located at a bottom portion 242 of the multi-pass heat exchanger 202. The collector allows the combustion gases to be vented out from the multi-pass heat exchanger 202 and also collects any condensate produced by the flue tubes as a byproduct of the combustion process. The collector may be a polymer material, however, other types of materials are also possible.

[0038] The multi-pass heat exchanger 202 may be more efficient than existing heat exchangers by allowing the heat of combustion gases within the heat exchanger 202 to be reduced from approximately 2100 F. to approximately 120 F. when the combustion gases are exhausted from the multi-pass heat exchanger 202 (based on the transference of the heat from the multi-pass heat exchanger 202). For example, the heat may be approximately 1800-2100 F. in the first flue tube 204, may be approximately 1200-1400 F. upon entering the second-pass flue tubes 206, 208, 210, and 212, may be below 500 F. upon entering the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240, and may be approximately 120 F. or below upon exiting the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240, resulting in an approximately 95% efficiency of the multi-pass heat exchanger 202. The final temperature at the end of the process may also depend on the altitude at which the multi-pass heat exchanger 202 is provided and the set point of the water heater.

[0039] In embodiments, the second-pass flue tubes 206, 208, 210, and 212 may be 3 in diameter, and the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 may be 2 in diameter. However, the size, shape, number, arrangement, etc. of the first-pass flue tube 204, second-pass flue tubes 206, 208, 210, and 212, and third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 is merely exemplary. For example, in other embodiments, the number of second-pass flue tubes may be increased from four to six and the number of third-pass flue tubes may be decreased.

[0040] Additionally, the second-pass flue tubes 206, 208, 210, and 212 may also include one or more dimples to slow the progression of the combustion heat through the second-pass flue tubes 206, 208, 210, and 212, which provides for maximum transference of heat from the heat exchanger 202 to the water in the water heater. Dimples may also be provided on the first-pass flue tube 204, the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240, and/or in any other combination of the different flue tubes.

[0041] In some embodiments, the second-pass flue tubes 202, 208, 210, and 212 may be substantially parallel to the first-pass flue tube 204 after curving/turning upward. The second-pass flue tubes 206, 208, 210, and 212 may branch out from the first-pass flue tube 204 proximal to a bottom end of the water tank 201 and may extend upward for a substantial portion of the height of the water tank 201. In some embodiments, the second-pass flue tubes 206, 208, 210, and 212 may have curves or other variations extending upward toward the top opening of the water tank 502. Top ends of the second-pass flue tubes 206, 208, 210, and 212 may be connected to the third-pass flue tubes via the diverters (not shown in FIG. 2 but shown in further detail in at least FIG. 10B, for example).

[0042] In some embodiments, the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 may extend in the cavity of the water tank 201 from the diverters connecting the third-pass flue tubes to the second-pass flue tubes to a bottom end of the water tank 201. Hot gas from the second-pass flue tubes 206, 208, 210, and 212 flows to the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 through the diverters connecting the second-pass flue tubes and the third-pass flue tubes.

[0043] In some embodiments, the bottom end openings of the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 may be terminated in the bottom assembly (for example, bottom assembly 106 shown in FIG. 1) through openings in a top cover of the bottom assembly. For example, the bottom assembly may include a bottom flue, and hot gas flowing through the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 may flow to the bottom flue and exit the bottom assembly through a hot gas outlet of the bottom assembly.

[0044] In some embodiments, the first-pass flue tube 204, the second-pass flue tubes 206, 208, 210, and 212, and the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 may be configured with respect to each other to allow for placing the hot water outlet (for example, hot water outlet 110 shown in FIG. 1) in the top cover assembly (for example, top cover assembly 104 of FIG. 1) of the water heater 200. For example, the second-pass flue tubes 206, 208, 210, and 212 may be intermingled with the third-pass flue tubes 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, and 240 around the first-pass flue tube 204. The second-pass flue tubes 206 and 208 may be less than ninety degrees apart from each other relative to the circle defining a cross-section of the hot water heater 200, and the second-pass flue tubes 210 and 212 are less than ninety degrees apart from each other relative to the circle defining the cross-section of the hot water heater 200. Further, the second-pass flue tubes 206 and 208 may each be greater than 90 degrees apart from the second-pass flue tubes 210 and 212 relative to the circle defining the cross-section of the hot water heater 200. Each second-pass flue tube 206, 208, 210, and 212 may also be flanked by one of the third-pass flue tubes 214, 216, 218, 220, 230, 232, 234, and 236, where two of the third-pass flue tubes 214, 216, 218, 220, 230, 232, 234, and 236 may be interspersed between two of the second-pass flue tubes 206, 208, 210, and 212. Further, the third-pass flue tubes 222, 224, 226, and 228 may be disposed in area 240 between the third-pass flow tubes 220 and 230.

[0045] In general, the third-pass flue tubes 214, 216, 218, 220, 230, 232, 234, and 236 may each be spaced from an adjacent one of the second-pass flue tubes 206, 208, 210, and 212 by the same circumferential distance relative to the circle defining the cross-section of the hot water heater 200. As such, compared to third-pass flue tubes that are between second-pass flue tubes and that are separated by less than ninety degrees relative to the circle defining the cross-section of the hot water heater 200, a much larger circumferential space relative to the circle defining the cross-section of the hot water heater 200 may exist between third-pass flue tubes 214 and 236 that are between second-pass flue tubes 206 and 212. The much larger circumferential space relative to the circle defining the cross-section of the hot water heater 200 between the third-pass flue tubes 214 and 236 aligns with the top water outlet. This allows the water heater 200 to have the top water outlet without degrading the thermal efficiency of the water heater 200.

[0046] FIG. 3A illustrates a perspective view of another heat exchanger 302 provided inside a water heater 300. The heat exchanger 302 includes a first pass-flue tube 304, four second-pass flue tubes (second pass-flue tubes 306, 308, 310, 312) connected to the first-pass flue tube 304, and eight third-pass flue tubes connected to the second-pass flue tube (for example, third-pass flue tubes 314 and 316 are visible in FIG. 3A). Particularly, the third-pass flue tubes 314 and 316 are shown as being connected to the second-pass flue tube 312 via diverter 318. Any of the other third-pass flue tubes may also be connected to a respective second-pass flue tube using a similar type of diverter. The diverters are provided underneath a top pan 322 of the water heater 300 such that the hot gas from the combustion system (not shown in FIGS. 3A-3B) flows through the heat exchanger 302 underneath the top pan 322. This is in contrast to some water heaters, where a diverter may instead be provided above the top pan (for example, as shown in FIG. 7) for directing hot gas between the second- and third-pass flue tubes.

[0047] In certain embodiments, the center first-pass flue tube 304 may be six inches in diameter. The second-pass flue tubes may be J tubes or straight tubes that are 2.5 inches in diameter. The third-pass flue tubes may be J tubes or straight tubes that are 2 inches in diameter. However, any other configuration is also possible as well such as using straight tubes with an elbow (e.g., 90 degree elbow) instead of J tubes.

[0048] FIG. 3A also shows that the flue tubes of the heat exchanger 302 include a plurality of dimples 320 provided at various intervals down the length of the flue tubes. FIG. 3B shows a close-up view of the second-pass flue tube 312 to more clearly depict the dimples 320 provided on the second-pass flue tube.

[0049] A flue tube may begin as a cylindrical (or substantially cylindrical) shape. However, according to certain example embodiments, the flue tube may undergo one or more processes (e.g., crimping, etc.) so that the flue tube (and, more specifically, the inner surface of the flue tube) is non-cylindrical. An example of a tool that may be used to produce the dimples is shown in FIGS. 12A-12B.

[0050] In this way, using example embodiments, fluids (e.g., hot gases that are byproducts of the combustion of the fuel/air mixture in the heat exchanger 302) that flow through the cavities of the flue tubes can be better controlled, resulting in a more efficient process and less stress on the flue tubes due to pressure, which in turn results in less fuel consumed, lower costs incurred, and longer useful life of the various components (e.g., flue tubes) of the heat exchanger. In some instances, the dimples may also create flow path obstructions to facilitate heat transfer with the water. That is, the dimples may function similarly to baffles, but without requiring a separate component (the baffles) that would need to be installed into the flue tubes.

[0051] In this example, the flue tube has an inner surface and an outer surface (also called an outer wall surface). At regular intervals, a number of crimps are made in the flue tube, creating a number of dimples 320. The dimples 320 on the flue tube may be simultaneously created on opposing sides of the flue tube, creating a mirror image of inward dimples 320. In embodiments in which the flue tube 312 is made from carbon steel, there is a maximum depth into the cavity that the dimple 320 may be crimped without breaking the flue tube. Therefore, the dimples 320 in a flue tube of carbon steel construction may not be able to be crimped such that opposing dimples come in contact with one another. In other words, the cavity is continuous along the length of the flue tube 312, although, in some locations (e.g., where the dimples 320 are formed) of the flue tube 312, the cavity is smaller relative to other locations (e.g., where no dimples 320 are formed) of the flue tube 312.

[0052] In embodiments, the interior of the cavity of the flue tube may be coated with a material, such as porcelain. The third pass tubes may expose condensate formation in flue gas and this condensate may be acidic in nature. Accordingly, the porcelain or enamel coating (or other type of coating) protects the tubes from corrosion. As previously indicated, the dimples may not come directly into contact with one another. This is also advantageous because it provides spacing for the coating to be applied to the flue tubes, whereas if opposing dimples were to be touching, then there may not exist sufficient space for the coating to be applied to the flue tubes.

[0053] As discussed above, opposing pairs of dimples 320 may be created at regular intervals along the length of the flue tube in a top-bottom (when viewed from above) orientation. In addition, opposing pairs of dimples 320 may be created at regular intervals along the length of the flue tube in a left-right (when viewed from above) orientation. The left-right oriented dimples 320 may also be equally spaced along the length of the flue tube 312 relative to the adjacent top-bottom oriented dimples 320. In other words, one pair of dimples 320 can be rotated 90 degrees (or any other degrees) about the longitudinal axis of the flue tube 312 relative to an adjacent pair of dimples 320.

[0054] More generally, a first set of pairs of dimples may be formed at regular intervals of a first length along the length of the flue tube. Each pair of dimples in the first set are positioned on opposite sides of the flue tube (e.g., radially offset by 180 degrees). Likewise, a second set of pairs of dimples may be formed at regular intervals of a second length along the length of the flue tube. Each pair of dimples in the second set are positioned on opposite sides of the flue tube (e.g., radially offset by 180 degrees). The first length and the second length may be the same or different lengths. The dimples in the first set are radially offset relative to the dimples of the second set (e.g., radially offset by 90 degrees). The dimples of the first set are longitudinally offset relative to the dimples of the second set such that the dimples of the first set and the dimples of the second set alternate along the length of the flue tube.

[0055] FIGS. 4A-4C illustrate side views of various heat exchanger configurations. FIGS. Particularly, FIG. 4A shows a first heat exchanger 400, FIG. 4B shows a second heat exchanger 410 and FIG. 4C shows a third heat exchanger 420. 5A-5C illustrate top-down views of the various heat exchanger configurations of FIGS. 4A-4C that more clearly illustrate the configuration of the flue tubes included in the various heat exchangers shown in FIGS. 4A-4C. For example, heat exchanger 500 corresponds to heat exchanger 400, heat exchanger 530 corresponds to heat exchanger 410, and heat exchanger 540 corresponds to heat exchanger 420.

[0056] Beginning with FIGS. 5A-5B, heat exchangers 500 and 530 are shown as including a first-pass flue tube 501, four second-pass flue tubes (for example, first second-pass flue tube 502, second second-pass flue tube 510, third second-pass flue tube 516, and fourth second-pass flue tube 522), and eight third-pass flue tubes (for example, first third-pass flue tube 504, second third-pass flue tube 506, third third-pass flue tube 508, fourth third-pass flue tube 512, fifth third-pass flue tube 514, sixth third-pass flue tube 518, seventh third-pass flue tube 520, and eighth third-pass flue tube 524). Heat exchangers 500 and 530 differ in that the diameter of the flue tubes is smaller in the heat exchanger 530 than the heat exchanger 500. For example, the second-pass flue tubes and third-pass flue tubes in the heat exchanger 500 may be 2.5 inches and 2 inches in diameter respectively. In contrast, the second-pass flue tubes and third-pass flue tubes in the heat exchanger 530 may both be 2 inches in diameter. This illustrates that the dimensions of the flue tubes in any of the heat exchangers described herein may vary and may not necessarily be limited to a single configuration.

[0057] Each of the second-pass flue tubes is also connected to two third-pass flue tubes. For example, first second-pass flue tube 502 is shown as being connected to first third-pass flue tube 504 and second third-pass flue tube 506, second second-pass flue tube 510 is shown as being connected to third third-pass flue tube 508 and fourth third-pass flue tube 512, third second-pass flue tube 516 is shown as being connected to fifth third-pass flue tube 514 and sixth third-pass flue tube 518, and fourth second-pass flue tube 522 is shown as being connected to seventh third-pass flue tube 520 and eighth third-pass flue tube 524.

[0058] Turning to FIG. 5C, the heat exchanger 540 is shown in a different configuration that includes only three second-pass flue tubes. The heat exchanger 540 includes fewer materials than the heat exchangers 500 and 530 and therefore provides for easier manufacturing.

[0059] Particularly, the heat exchanger 540 includes a single first-pass flue tube 541, first second-pass flue tube 556, second second-pass flue tube 550, and third second-pass flue tube 544 connected to first-pass flue tube 541. The heat exchanger 540 also includes first third-pass flue tube 554 and second third-pass flue tube 558 connected to first second-pass flue tube 556, third third-pass flue tube 548 and fourth third-pass flue tube 552 connected to second second-pass flue tube 550, and fifth third-pass flue tube 542 and sixth third-pass flue tube 546 connected to third second-pass flue tube 544.

[0060] In the configurations shown in FIGS. 5A-5C, hot gas from the combustion system (for example, combustion system 108 shown in FIG. 1) flows down into the first-pass flue tube and up into the second-pass flue tubes. Subsequently, the hot gas flows down into the third-pass flue tubes. Although the heat exchanger configurations described herein include hot gas flowing down into the first-pass flue, up into the second-pass flue tubes, and down into the third-pass flue tubes, this is merely exemplary and heat exchangers may also be configured to flow in any other direction through the flue tubes.

[0061] FIG. 6 illustrates a diverter 602 of a heat exchanger 600 (the water heater in which the heater exchanger 600 is provided is not shown in FIG. 6). The diverter 602 is shown as being provided on a top surface of the top pan 604 (for example, part of the top cover assembly 104 shown in FIG. 1). In a heat exchanger including this particular diverter 602, hot gas flows from the second-pass flue tubes up into the diverter 602 and back down into the third-pass flue tubes.

[0062] FIG. 7 illustrates a perspective view of another diverter 804 of a heat exchanger 702 provided within a water heater 700. FIG. 8 illustrates a close-up side view of the diverter 704 of FIG. 7. Particularly, the diverter 704 is provided in the form of a second, smaller pan that is provided underneath the existing top pan 705. That is, the diverter 704 may be provided entirely beneath the top pan 705. For example, the top pan may be 24 inches in diameter and the second pan forming the diverter 704 may be 22 inches in diameter (these numbers are not intended to be limiting). During operation of the water heater 700, hot gasses flow from the first-pass flue tube, into the second-pass flue tubes, from the second-pass flue tubes into the diverter 704 (underneath the top pan 705), and from the diverter 704 into the third-pass flue tubes. By positioning the diverter 704 beneath the top pan, less heat is lost through the diverter 704 than if it were positioned above the top pan (such as shown in FIG. 6).

[0063] FIG. 9A illustrates a perspective view of another diverter 904 of a heat exchanger 902 provided in a water heater 900. FIG. 9B illustrates a close-up side view of the diverter 904 of FIG. 9A. In contrast with the diverter 804 of FIG. 8, which is a full pan provided underneath the top pan of the water heater, the diverter 904 in FIG. 9 is a horseshoe-shaped diverter that conforms to the arrangement of the second and third-pass flue tubes. The diverter 904 is also provided underneath the top pan of the water heater 900. During operation of the water heater 900, hot gasses flow from the first-pass flue tube, into the second-pass flue tubes, from the second-pass flue tubes into the diverter 904 (underneath the top pan), and from the diverter 904 into the third-pass flue tubes. Similar to the above, by positioning the diverter 904 beneath the top pan, less heat is lost through the diverter 904 than if it were positioned above the top pan (such as shown in FIG. 7).

[0064] FIG. 10A illustrates a perspective view of another diverter configuration for a heat exchanger 1002 provided in a water heater 1000. FIG. 10B illustrates a close-up side view of the diverter configuration of FIG. 10A. In the diverter configuration shown in FIGS. 10A-10B, the third-pass flue tubes are directly connected to the second-pass flue tubes, rather than both the second-pass flue tubes and third-pass flue tubes being connected to a separate diverter that is provided on the top pan 1012 (such as the diverter 702 shown in FIG. 7). For example, first third-pass flue tube 1004 and second third-pass flue tube 1008 are shown as being directly connected to second-pass flue tube 1010 via connection point 1006. In this configuration, hot gas from the combustion system (not shown in the figure) flows into the first-pass flue tube, up into the second-pass flue tubes, and then directly back into the third-pass flue tubes, rather than first flowing into a separate diverter.

[0065] FIGS. 11A-11B illustrate close-up front views of dimples of two exemplary flue tubes, which may be any of the flue tubes described herein. For example, FIGS. 11A-11B illustrate flue tube 1100 including first dimple 1102 and second dimple 1104 and flue tube 1110 including first dimple 1112 and second dimple 1114. FIGS. 11C-11D illustrate cross-section side views of the flue tubes 1100 and 1110. For example, FIG. 11C shows first dimple 1102 and an adjacent third dimple 1104 (not shown in the perspective of FIG. 11A) and FIG. 11D shows first dimple 1112 and an adjacent third dimple 1116 (not shown in the perspective of FIG. 11B). The flue tube 1100 may be an exemplary second-pass flue tube and the flue tube 1110 may be an exemplary third-pass flue tube.

[0066] As aforementioned, in embodiments in which the flue tubes of the heat exchanger are made from a carbon steel material, the specific arrangement, size, and shape of the dimples is critical given that carbon steel is a more brittle material than, for example, stainless steel. For example, if the ratio of dimple depth to the spacing between dimples is above a certain threshold, the material may be likely to break. An example of a ratio is 3.5 given a spacing of 2.75 inches and a depth of 0.8 inches. However, other ratios may also be acceptable as well and this is not intended to be limiting. Accordingly, even if existing heat exchangers use flue tubes that include dimples, the arrangement, size, and shape of the dimples in these existing heat exchangers cannot simply be applied to the heat exchanger made using a carbon steel material. The arrangement, size, and shape of the dimples as described herein are optimized to allow for maximum thermal efficiency of the heat exchanger (for example, 95% or greater efficiency) while maintaining the integrity of the structure of the flue tubes. FIGS. 11A-11D provide examples of arrangement, size, and shape of the dimples that allows for this balance between thermal efficiency and material integrity. It should be noted that other arrangements, sizes, and shapes may also be possible that still provide this balance. Additionally, the arrangement, size, and shape may differ depending on the type of material that is used (for example, if the material is different than carbon steel).

[0067] Beginning with FIGS. 11A-11B, exemplary spacing between dimples provided along the length of a flue tube is shown. For example, FIGS. 11A-11B show a spacing of 2.75 inches between the center points of the first dimple and the second dimple 1104 (and likewise between the first dimple 1112 and the second dimple 1114). However, other amounts of spacing may also be applicable depending on various factors, such as the depth of the dimples used, the type of coating provided inside the tubes, etc. Although only two dimples are shown in FIGS. 11A-11B, the spacing may also be applicable to any other number of dimples provided along the length of a given flue tube.

[0068] Turning to FIGS. 11C-11D, side views including additional exemplary dimensions of the flue tubes 1100 and 1110 are shown. For example, FIGS. 11C 11-D show that a diameter of the flue tube 1100 is 2.5 inches and a diameter of the flue tube 1110 is 2 inches. At a location within the cavity of the flue tube 1100 at which the first dimple 1102 is indented (and a third dimple 1106 is intended on the opposite side of the cavity), the distance between the first dimple 1102 and the third dimple 1106 may be 1.3 inches. Likewise, at a location within the cavity of the flue tube 1110 at which the first dimple 1112 is indented (and a third dimple 1116 is intended on the opposite side of the cavity), a distance between the first dimple 1112 and the third dimple 1116 may be 0.78 inches. Further, the depth of the first dimple 1102 of the flue tube 1100 and the depth of the first dimple 1112 of the flue tube 1110 are both shown as 0.8 inches.

[0069] FIG. 12A illustrates a side view of a tool 1200 used to produce dimples in a flue tube 1202. FIG. 12B illustrates a perspective view of the same tool 1200. For example, the tool 1200 may include one or more pressing elements (for example, pressing element 1202, 1204, 1206, 1206, etc.). When the tool 1200 is aligned with a tube, the pressing elements may be positioned at the locations along the length of the tube where it is desired for dimples to be formed. The pressing elements may then be pressed into the tube a certain distance (the desired distance of the dimples) to form the dimples in the tube). Given that the dimples are produced at the same time, the process is faster and the material resistance is counterbalanced from opposing sides. This is merely one example of a type of tool that may be used to produce the dimples and other tools may also be used as well. Similar to the description above, the pressing elements 1202 and 1206 may be located at a first longitudinal location and the pressing elements 1204 and 1208 may be located at a second longitudinal location where the first and second longitudinal locations are offset from each other.

[0070] Any example flue tubes, or portions thereof, described herein can be made from a single piece (e.g., as from a mold, injection mold, die cast, 3-D printing process, extrusion process, stamping process, crimping process, and/or other prototype methods). In addition, or in the alternative, example flue tubes (or portions thereof) can be made from multiple pieces that are mechanically coupled to each other. In such a case, the multiple pieces can be mechanically coupled to each other using one or more of a number of coupling methods, including but not limited to epoxy, welding, fastening devices, compression fittings, mating threads, and slotted fittings. One or more pieces that are mechanically coupled to each other can be coupled to each other in one or more of a number of ways, including but not limited to fixedly, hingedly, removeably, slidably, and threadably.

[0071] It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the disclosure.

[0072] Although specific embodiments of the disclosure have been described, numerous other modifications and alternative embodiments are within the scope of the disclosure. For example, any of the functionality described with respect to a particular device or component may be performed by another device or component. Further, while specific device characteristics have been described, embodiments of the disclosure may relate to numerous other device characteristics. Further, although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments. Conditional language, such as, among others, can, could, might, or may, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments may not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.