Heat exchanger including flue flow path guide system

Abstract

A guide system including a top end, a bottom end, a lumen and a plurality of openings, the system is disposed within a coil lumen at the bottom end of the heat exchanger coil with the bottom end of the system extending beyond the bottom end of the coil in a direction from the top end to the bottom end of the coil, the system configured in a shape of the coil lumen and the openings are disposed on the bottom end of the system, wherein the heat exchanger is configured to channel the flue flow from a burner through a path to heat a fluid flow of the coil before entering the lumen of the system via the openings to avoid a pressure drop due to a tendency for the flue flow to follow a path defined by a shape of the bottom end of the coil.

Claims

1. A method of balancing a flue flow about a central axis of a coil of a heat exchanger with a flue guide system, the coil having a top section, a bottom section, a top end, a bottom end at which a last coil loop of the coil terminates and a lumen, the coil configured for receiving a fluid flow at one of the top end and bottom end of the coil and channeling the fluid flow to the other one of the top end and bottom end of the coil, a burner disposed at the top section of the coil within the lumen of the coil, the burner configured to receive an air-fuel flow urging a flue flow of the burner in a general direction from the top end of the coil to the bottom end of the coil, an open-bottom and closed-top tube configured in a shape of the lumen of the coil, the closed-top tube disposed at the bottom section of the coil within the lumen of the coil to cooperatively form a path with a housing within which the bottom section of the coil is disposed and the guide system having a top end, a bottom end, a lumen and a plurality of openings of different sizes, the guide system is disposed within the lumen of the coil at the bottom end of the coil with the bottom end of the guide system extending beyond the bottom end of the coil in a direction from the top end of the coil to the bottom end of the coil, the guide system is configured in a shape of the lumen of the coil and the plurality of openings are disposed about the central axis of the coil on the guide system, wherein the heat exchanger is configured to channel the flue flow from the burner through the path to heat the fluid flow before the flue flow entering the lumen of the guide system via the plurality of openings, said method comprising disposing the plurality of openings of different sizes that progressively differ in size in a direction from a starting point of the last coil loop to the bottom end of the coil.

2. The method of claim 1, wherein said disposing step comprises disposing the plurality of openings of different sizes that progressively increase in size in a direction from a starting point of the last coil loop to the bottom end of the coil.

3. The method of claim 1, wherein the plurality of openings of the guide system comprises at least one cutout made on the bottom end of the guide system.

4. The method of claim 1, wherein the plurality of openings of the guide system comprises at least one leg upon which the closed-top tube is supported.

5. A heat exchanger for heating a fluid flow, said heat exchanger comprising: (a) a coil comprising a central axis, a top section, a bottom section, a top end, a bottom end and a lumen, said coil configured for receiving the fluid flow at one of said top end and bottom end of said coil and channeling the fluid flow to the other one of said top end and bottom end; (b) a burner disposed at said top section within said lumen of said coil, said burner configured to receive an air-fuel flow urging a flue flow of said burner in a general direction from said top end of said coil to said bottom end of said coil; (c) a housing within which said coil is disposed; (d) a sleeve configured to surround the coil, said sleeve disposed about said central axis of said coil within said housing, said sleeve comprising a plurality of top apertures disposed in a manner to coincide with said top section of said coil and a plurality of bottom apertures disposed in a manner to coincide with said bottom section of said coil and the flue flow is urged from within said lumen of said coil to a first space outside of said lumen of said coil in a space defined by said housing and said sleeve at said top section of the coil through said plurality of top apertures of said sleeve; (e) an open-bottom and closed-top tube configured in a shape of said lumen of said coil, said closed-top tube disposed at said bottom section within said lumen of said coil to cooperatively form a path with said sleeve to guide the flue flow that enters a second space defined by said sleeve and said closed-top tube through said plurality of bottom apertures; and (f) a guide system comprising a top end, a bottom end, a lumen and a plurality of openings, said guide system disposed within said lumen of said coil at said bottom end of said coil with said bottom end of said guide system extending beyond said bottom end of said coil in a direction from said top end of said coil to said bottom end of said coil, wherein said guide system is configured in a shape of said lumen of said coil and said plurality of openings are disposed on said bottom end of said guide system, wherein said heat exchanger is configured to channel the flue flow from said burner through said first space and said path to heat the fluid flow before entering said lumen of said guide system via said plurality of openings.

6. The heat exchanger of claim 5, wherein said plurality of openings of said guide system comprises at least one cutout made on said bottom end of said guide system.

7. The heat exchanger of claim 5, wherein said plurality of openings of said guide system comprises at least one leg upon which said closed-top tube is supported.

8. The heat exchanger of claim 5, further comprising a heat shield disposed atop said closed-top tube to prevent overheating of a top portion of said closed-top tube.

9. The heat exchanger of claim 8, wherein said heat shield is configured to be coupled to said closed-top tube by a notch-locator pair to remove the need of a fastener for coupling said closed-top tube to said heat shield.

10. The heat exchanger of claim 5, wherein said heat shield comprises a ceramic material.

11. The heat exchanger of claim 5, wherein said closed-top tube further comprises a locator on a top portion of said closed-top tube, said locator is configured to be mated to a notch of a heat shield for securing the heat shield atop said closed-top tube.

12. The heat exchanger of claim 5, said plurality of openings are configured to vary in size along a periphery of said bottom end of said guide system.

13. The heat exchanger of claim 5, said plurality of top apertures are configured to vary in size along a length of said sleeve.

14. A guide system for guiding a flue flow of a heat exchanger configured for heating a fluid flow, the heat exchanger having a coil having a top section, a bottom section, a top end, a bottom end and a lumen, the coil configured for receiving the fluid flow at one of the top end and bottom end of the coil and channeling the flow to the other one of the top end and bottom end, a burner disposed at the top section of the coil within the lumen of the coil, the burner configured to receive an air-fuel flow urging a flue flow of the burner in a general direction from the top end of the coil to the bottom end of the coil, a housing within which the coil is disposed, an open-bottom and closed-top tube configured in a shape of the lumen of the coil, the closed-top tube disposed at the bottom section of the coil within the lumen of the coil to cooperatively form a path with the housing within which the bottom section of the coil is disposed, said guide system comprising: a top end, a bottom end, a lumen and at least one aperture, said guide system is disposed within the lumen of the coil at the bottom end of the coil with said bottom end of said guide system extending beyond the bottom end of the coil in a direction from the top end of the coil to the bottom end of the coil, said at least one aperture disposed between said top end and said bottom end of said guide system for allowing the flue flow to enter said lumen of said guide system from the path, wherein the heat exchanger is configured to channel the flue flow from the burner through the path to heat the fluid flow before entering the lumen of said guide system via said at least one aperture.

15. The guide system of claim 14, the coil having a plurality of coil loops, said at least one aperture of said guide system is aligned with one of said coil loops.

16. The guide system of claim 14, the coil having a plurality of coil loops, said at least one aperture is a plurality of apertures aligned with at least one of said coil loops.

17. The guide system of claim 14, the coil having a plurality of coil loops, said at least one aperture is a plurality of apertures that differ in size from a closed-top end to an open-bottom end of said open-bottom and closed-top tube.

18. The guide system of claim 14, the coil having a plurality of coil loops, said at least one aperture is a plurality of apertures that increase in size from a closed-top end to an open-bottom end of said open-bottom and closed-top tube.

19. The guide system of claim 14, wherein the coil comprises a central axis and said guide system further comprises a sleeve configured to surround the coil, said sleeve disposed about said central axis of the coil, said sleeve comprising a plurality of top apertures disposed in a manner to coincide with said top section of the coil and a plurality of bottom apertures disposed in a manner to coincide with said bottom section of the coil and the flue flow is urged from within the lumen of the coil to outside of the lumen of the coil at said top section of the coil through said plurality of top apertures of said sleeve and the flue flow is configured to enter said lumen of said guide system through said plurality of bottom apertures of said sleeve and said at least one aperture of said guide system.

20. The guide system of claim 14, wherein the coil having a plurality of coil loops and a central axis, said guide system further comprises at least one strip configured to be disposed between said plurality of coil loops, said guide system further comprises a sleeve configured to surround the coil, said sleeve disposed about said central axis of the coil, said sleeve comprising a plurality of top apertures disposed in a manner to coincide with said top section of the coil and a plurality of bottom apertures disposed in a manner to coincide with said bottom section of the coil and the flue flow is urged from within the lumen of the coil to outside of the lumen of the coil at said top section of the coil through said plurality of top apertures of said sleeve and the flue flow is configured to enter said lumen of said guide system through said plurality of bottom apertures of said sleeve, through a space in which said bottom section of the coil is disposed, said space defined by said at least one strip, said sleeve and said guide system and through said at least one aperture of said guide system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order that the manner in which the above-recited and other advantages and objects of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

(2) FIG. 1 depicts a prior art heat exchanger where a flue flow is configured to simply trace the bottom loop of the coil before exiting the heat exchanger to the exhaust of the heat exchanger.

(3) FIG. 2 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder disposed atop a plurality of support legs where the guide system is seated within the lumen of a heat exchanger coil.

(4) FIG. 2A is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder including a plurality of apertures, where the guide is seated within the lumen of a heat exchanger coil.

(5) FIG. 3 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder having a plurality of cutouts disposed on the bottom edge of the cylinder where the guide system is seated within the lumen of a heat exchanger coil.

(6) FIG. 4 is top perspective cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder having a plurality of cutouts disposed on the bottom edge of the cylinder where the guide system is seated within the lumen of a heat exchanger coil.

(7) FIG. 5 is a top close-up perspective view of the embodiment of a present guide system shown in FIG. 3 where the guide system is seated within the lumen of a heat exchanger coil.

(8) FIG. 6 is a top close-up perspective view of one embodiment of a present guide system, depicting a plurality of apertures disposed on a present guide system

(9) FIG. 7 is a top perspective view of one embodiment of a present guide system, depicting a manner in which a heat shield is coupled to the guide system.

(10) FIG. 8 is a bottom perspective view of one embodiment of a present guide system, depicting a manner in which a heat shield is coupled to the guide system.

(11) FIG. 9 is a diagram depicting the openings of a present guide system and their relationship with respect to the last loop of a heat exchanger coil.

(12) FIG. 10 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder having a plurality of cutouts disposed on the bottom edge of the cylinder where the guide system is seated within the lumen of a heat exchanger coil.

(13) FIG. 11 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder including a plurality of apertures, where the guide is seated within the lumen of a heat exchanger coil.

PARTS LIST

(14) 2—heat exchanger 4—lumen of coil 6—flow of fluid to be heated 8—coil 10—housing 12—open-bottom and closed-top tube 14—guide system 16—lumen of guide system 18—opening 20—aperture 22—cutout 24—leg 26—burner 28—heat shield 30—blower 32—flue flow 34—structure 36—last or most downstream loop of coil 38—notch 40—locator 42—edge of tube 44—edge of tube 46—average height of opening 48—average height of opening 50—exhaust 52—right seam 54—left seam 56—air-fuel mixture flow caused by blower 58—central axis of coil or guide system 60—sleeve 62—top aperture 64—bottom aperture 66—solid strip 68—slit strip

Particular Advantages of the Invention

(15) The present guide reduces the pressure drop of a flue gas flow by allowing flue gas to enter a centrally located space directly without having to trace a longer path along the last loop of a coil that causes an undesired pressure drop in the flue flow. In one embodiment, the present guide system also enhances heat transfer from a flue gas flow to a coil by having apertures suitably aligned with the interfaces between consecutive coil loops the coil.

(16) In one embodiment, the present guide may be constructed from a rectangular-shaped flat sheet with cutouts and subsequently joined with any suitable joining techniques at a seam or from a tube-shaped component with cutouts, thereby removing the need for forming a component in numerous steps or with advanced manufacturing techniques and tools. In one embodiment, the present guide system may be constructed simply as a cylinder or tube that is supported on legs formed at the bottom portion of a housing of the burner within which the cylinder is disposed.

Detailed Description of a Preferred Embodiment

(17) The term “about” is used herein to mean approximately, roughly, around, or in the region of. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 20 percent up or down (higher or lower).

(18) FIG. 1 depicts a prior art heat exchanger where a flue flow is configured to simply trace the bottom loop of the coil before exiting the heat exchanger to the exhaust of the heat exchanger. It shall be noted that in the heat exchanger depicted, the flue flow 32, upon arriving at the last (bottom) loop 36 of the coil 8, tends to flow around it, before exiting at the bottom of the heat exchanger. Note that a structure 34 disposed within the lumen of the coil forces the flue flow around the coil 8 at the lower section of the coil 8. Upon leaving the last loop of the coil 8, the flue flow 32 no longer serves a purpose except only to continue to exit such that a flue flow can continue to occur. The additional distance for the flue flow 32 to trace increases the requirement of a blower with a higher capacity, e.g., a larger blower. Applicants discovered that by configuring the exit portion of the coil in the manner disclosed elsewhere herein, the pressure drop caused by an additional path caused by the last loop 36 of the coil 8 can be significantly reduced.

(19) FIG. 2 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder disposed atop a plurality of support legs disposed substantially about the bottom periphery of the guide where the guide system is seated within the lumen of a heat exchanger coil 8. It shall be noted that a plurality of openings 18 of the guide system 14 that are formed by disposing a closed-top tube 12 atop a plurality of legs 24 upon which the closed-top tube 12 is supported and the plurality of openings 18 are disposed about the central axis 58 of the coil 8 or guide system 14. Flue flow 32 can occur readily through the openings 18 into the lumen 16 of the guide system. FIG. 2A is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder including a plurality of apertures 20, where the guide is seated within the lumen of a heat exchanger coil.

(20) FIG. 3 is a side cross-sectional view of one embodiment of a present guide system 14, depicting a guide formed of a cylinder having a plurality of cutouts 22 disposed on the bottom edge of the cylinder where the guide system is seated within the lumen of a heat exchanger coil. FIG. 4 is top perspective cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder having a plurality of cutouts disposed on the bottom edge of the cylinder where the guide system is seated within the lumen of a heat exchanger coil. FIG. 5 is a top close-up perspective view of the embodiment of a present guide system shown in FIG. 3 where the guide system is seated within the lumen of a heat exchanger coil.

(21) FIG. 6 is a top close-up perspective view of one embodiment of the present guide system, depicting a plurality of apertures 20 disposed on a tube 12 of a present guide system. It shall be noted that the plurality of apertures 20 are disposed between the top end and the bottom end of the tube 12 for allowing the flue flow to enter the lumen of the guide system 14 from the flue path as represented by arrows upstream of the lumen of the tube 12. The plurality of apertures 20 are preferably aligned with an interface between at least one set of two consecutive coil loops of the coil 8 such that the flue flow 32 can flow more readily around the loops that span or encompassed across the height of the tube 12.

(22) FIG. 7 is a top perspective view of one embodiment of the present guide system, depicting a manner in which a heat shield is coupled to the guide system. FIG. 8 is a bottom perspective view of one embodiment of the present guide system, depicting a manner in which a heat shield is coupled to the guide system. Again, it shall be noted, in this embodiment, flue flow 32 can occur readily through the openings 18 into the lumen 16 of the guide system, reducing the pressure drop cause by the flue flow 32 through the coil 8 to the exhaust 50. FIGS. 3-5 depict a heat exchanger 2 for heating a fluid flow 6. Note that the blower which provides an air-fuel mixture flow 56 is not shown in FIG. 4. Upon combustion in a burner 26, the air-fuel mixture flow 56 becomes a flue flow 32 that continues around the coil 8 to eventually exit through the exhaust 50. The heat exchanger includes a coil 8, a burner 26, a housing 10 within which the coil 8 is disposed, an open-bottom and closed-top tube 12 and a guide system 14. The coil 8 includes a top section, a bottom section, a top end, a bottom end and a lumen. The coil is configured for receiving the fluid flow at one of the top end and bottom end of the coil and channeling the fluid flow to the other one of the top end and bottom end. In the example shown herein, the fluid flow 6 is received at the bottom end of the coil 8 and exits at the top end of the coil 8. The burner 26, disposed at the top section of the coil 8 within the lumen 4 of the coil 8, is configured to receive an air-fuel flow brought to it by a blower 30, urging a flue flow 32 of the burner 26 in a direction from the top end of the coil to the bottom end of the coil 8. The open-bottom and closed-top tube 12 is configured in a shape of the lumen 4 of the coil 8, e.g., cylinder, and is disposed at the bottom section within the lumen 4 of the coil 8 to cooperatively form a path with the housing 10 within which the bottom section of the coil is disposed. The guide system 14 includes a top end, a bottom end, a lumen 16 and a plurality of openings 18 and it is disposed within the lumen 4 at the bottom end of the coil 8 with the bottom end of the guide system 14 extending beyond the bottom end of the coil 8 in a direction from the top end of the coil to the bottom end of the coil 8. The guide system 14 is configured in a shape of the lumen 4 of the coil 8 and the plurality of openings 18 are disposed on the bottom end of the guide system 14. The heat exchanger 2 is configured to channel the flue flow 32 from the burner 26 through the path upstream of the guide to heat the flue flow 32 before entering the lumen of the guide system 14 via the plurality of openings 18 to avoid a pressure drop due to a tendency for the flue flow 32 to follow a route defined by a shape of the bottom end or the last loop 36 of the coil 8.

(23) As shown in FIGS. 2-8, a heat shield 28, e.g., constructed from a ceramic material, is further disposed atop the tube 12 to prevent excessive heating that can occur on the top portion of the tube 12 at certain firing rates of the burner 26. In FIG. 2, the heat shield 28 is secured to the tube by means of a fastener. In FIGS. 3-8, the heat shield 28 can alternatively be secured to the tube 12 by means of a notch 38 and locator 40 pair to avoid the need of a fastener for securing the two parts. As shown in FIGS. 3-8, the notch 38 is disposed on a bottom surface of the heat shield 28 while its matching locator 40 is disposed on a top surface of the tube 12. A notch may alternatively be disposed on the tube 12 while its matching locator may be disposed on the heat shield 28 to achieve an equivalent coupling of the two parts.

(24) FIG. 9 is a diagram depicting the openings of a present guide system and their relationship with respect to the last loop of a heat exchanger coil. In constructing a tube of a guide system, a sheet, e.g., a steel sheet having two edges 42, 44, is first provided. Openings 18 are subsequently cut out, e.g., by stamping, or laser cutting, etc., from the sheet before the sheet is rolled to form a tube and the edges 42, 44 joined, e.g., by welding and other joining techniques, etc., to form a physical seam that is subsequently smoothened. In one embodiment as shown in FIGS. 7-8, the top of the tube is further sealed using a circularly shaped plate that is embossed to form a locator. In one embodiment not shown, the tube is configured to receive a heat shield atop the tube which also serves to seal the top end of the tube. In balancing the pressure drop of a flue flow along the periphery of the tube, the plurality of openings 18 are configured to vary in size along a periphery of the bottom end of the guide system. As the last loop of the coil 8 winds towards the end of the coil 8, the space between the coil 8 and the exhaust 50 decreases. Therefore, in order to maintain a balanced flue flow 32 across the openings 18 about the central axis 58 of the guide system or the coil, the size of the openings 18 is configured to increase as the last loop of the coil 8 winds towards the tip or the bottom end of the coil 8. In FIG. 9, a portion of coil 8 is shown laid flat and superimposed over the sheet to show the relationship between the coil 8 and the tube 12. For instance, the average height 46 of the openings 18 at the left seam 54 of the sheet increases to the average height 48 of the openings 18 at the right seam 52 of the sheet as the last loop of the coil 8 winds towards the end of the coil 8.

(25) FIG. 10 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder having a plurality of cutouts disposed on the bottom edge of the cylinder where the guide system is seated within the lumen of a heat exchanger coil. It shall be noted that although the general direction of the flue flow path remains similar to those disclosed elsewhere herein, i.e., from the top section of a coil to the bottom section of a coil 8, upon its generation at the burner, the flue flow exits the lumen 4 of the coil 8 through the coil loops disposed in the top section of the coil 8 to a space surrounding the coil 8, the space is defined by a housing 10 and a sleeve 60 before the flue flow 32 re-enters the lumen of the sleeve 60 at the upper end of the bottom section of the coil 8. Here, one or more solid strips 66 is disposed in between two consecutive coil loops at the interface between the lower coil loop of the top section of the coil and the upper coil loop of the bottom section of the coil to urge the flue flow 32 outside of the lumen of the coil 8 via a plurality of top apertures 62 before allowing it to re-enter the space surrounding bottom section of the coil 8 via a plurality of bottom apertures 64 before continuing around coil loops in the bottom section of the coil 8, one or more slit strips 68 and eventually through the plurality of openings 18 into the lumen of the coil 8. Again, in balancing the pressure drop of a flue flow along the periphery of an open-bottom and closed-top tube 12, the plurality of openings 18 are configured to vary in size along a periphery of the bottom end of the guide system as disclosed elsewhere herein. As the last loop of the coil 8 winds towards the bottom end of the coil 8, the space between the coil 8 and the exhaust 50 decreases. Therefore, in order to maintain a balanced flue flow 32 across the openings 18 about the central axis 58 of the guide system or the coil, the size of the openings 18 is configured to increase as the last loop of the coil 8 winds towards the tip or the bottom end of the coil 8. Therefore, a method to balance a flue flow about the central axis 58 of a coil 8 of a heat exchanger is shown herein with the use a flue guide system 14.

(26) The coil includes a top section, a bottom section, a top end, a bottom end at which a last coil loop of the coil terminates and a lumen. The coil is configured for receiving a fluid flow at one of the top end and bottom end of the coil and channeling the fluid flow to the other one of the top end and bottom end of the coil. A burner 26 is disposed at the top section of the coil 8 within the lumen of the coil 8 and it is configured to receive an air-fuel flow urging a flue flow of the burner in a general direction from the top end of the coil to the bottom end of the coil. An open-bottom and closed-top tube configured in a shape of the lumen of the coil is disposed at the bottom section of the coil within the lumen of the coil to cooperatively form a path with a sleeve within which the bottom section of the coil is disposed. The guide system 14 includes a top end, a bottom end, a lumen and a plurality of openings. The guide system is disposed within the lumen of the coil at the bottom end of the coil with the bottom end of the guide system extending beyond the bottom end of the coil in a direction from the top end of the coil to the bottom end of the coil. The guide system is configured in a shape of the lumen of the coil and the plurality of openings 18 are disposed about the central axis 58 of the coil 8 on the guide system. The heat exchanger is configured to channel the flue flow from the burner through the path to heat the fluid flow though the coil 8 before the flue flow enters the lumen of the guide system via the plurality of openings 18. The size of the plurality of openings 18 is configured to vary in a direction from a starting point of the last coil loop to the bottom end of the coil. In one embodiment, this is accomplished by increasing the size of the plurality of openings 18 in a direction from a starting point of the last coil loop to the bottom end of the coil. In one embodiment, the plurality of openings of the guide system includes at least one cutout made on the bottom end of the guide system. In another embodiment, the plurality of openings of the guide system includes at least one leg upon which the closed-top tube is supported. In one embodiment, the top apertures 62 are configured to increase in size in a direction from the bottom end of the coil 8 to the top end of the coil 8 to encourage balanced flue flow across the length of the coil 8, e.g., by increasing the size of a top aperture 62 at an upper end of the top section of the coil 8, the flue flow is urged to take this path even though the path is longer than a path through a top aperture 62 at a lower end of the top section of the coil 8, thereby balancing the pressure drop and hence the flue flow across the length of the coil 8 and eliminating any spots on the coil 8 that are heated excessively while other spots are insufficiently heated. In one embodiment, the plurality of bottom apertures 64 are configured to vary, e.g., increase, in size, in a direction from the top end of the coil 8 to the bottom end of the coil 8. For instance, the topmost bottom aperture 64 is smaller than the bottommost bottom aperture 64. If the top apertures 62 all assume the same size or the bottom apertures 64 all assume the same size, the flue flow can potentially intensify through paths of the least resistance or pressure drop, overheating parts of the coil 8 while insufficiently heating other parts of the coil 8.

(27) FIG. 11 is a side cross-sectional view of one embodiment of a present guide system, depicting a guide formed of a cylinder including a plurality of apertures, where the guide is seated within the lumen of a heat exchanger coil. The guide system is useful for guiding a flue flow of a heat exchanger configured for heating a fluid flow, e.g., water. The heat exchanger includes a burner, a housing and a coil having a top section, a bottom section, a top end, a bottom end and a lumen. The coil which is disposed within the housing, receives the fluid flow at one of the top end and bottom end of the coil and channels the flow to the other one of the top end and bottom end. The burner is disposed at the top section of the coil within the lumen of the coil, the burner configured to receive an air-fuel flow urging a flue flow of the burner in a general direction from the top end of the coil to the bottom end of the coil. There is provided an open-bottom and closed-top tube 12 configured in a shape of the lumen of the coil, the closed-top tube disposed at the bottom section of the coil within the lumen of the coil to cooperatively form a path with the housing within which the bottom section of the coil is disposed. The guide system includes a top end, a bottom end, a lumen and a plurality of apertures 20 and the guide system is disposed within the lumen of the coil at the bottom end of the coil with the bottom end of the guide system extending beyond the bottom end of the coil in a direction from the top end of the coil to the bottom end of the coil. The plurality of apertures 20 disposed between the top end and the bottom end of the guide system are useful for allowing the flue flow to enter the lumen of the guide system from the path, wherein the heat exchanger is configured to channel the flue flow from the burner through the path to heat the fluid flow through the coil before the flue flow enters the lumen of the guide system via the plurality of apertures 20 to avoid a pressure drop due to a tendency for the flue flow to follow a route defined by a shape of the bottom end of the coil. It shall be noted that only one or more solid strips 66 are used. The strip 66 may be disposed between two consecutive coil loops as a single continuous piece. However, multiple shorter solid strips may be disposed end-to-end to form a single continuous solid strip. The solid strip or strips 66 aid in guiding the flue flow 32 from the space because the housing 10 and the sleeve 60 through the space between the sleeve 60 and the guide system 14 bounded by solid strips 66 disposed between consecutive coil loops.

(28) In one embodiment, the coil includes a plurality of coil loops, the plurality of apertures 20 of the guide system are aligned with the coil loops. In one embodiment, the plurality of apertures differ in size from an open-bottom end to a closed-top end of the open-bottom and closed-top tube. In one embodiment, the plurality of apertures 20 increase in size from a closed-top end to an open-bottom end of the open-bottom and closed-top tube 12. By increasing the size of the apertures 20 which coincide with the coil loops, from the closed-top end to an open-bottom end of the open-bottom and closed-top tube 12 along the coil loops, pressure drop through the apertures 20 are balanced, causing even flue flow through these apertures 20 and removing concentrations of the flue flow on certain parts of the coil 8 while insufficiently heating other parts of the coil 8. In one embodiment as shown in FIG. 11, the bottom apertures 64 coinciding with the coil loops of the bottom section of coil 8 and apertures 20 are sized similarly to the coincident apertures 20. In another embodiment, the sleeve 60 does not extend downwardly beyond the uppermost coil loop of the bottom section of the coil 8. To reach the lumen 16 of the guide system, the flue flow 32 does not need to traverse apertures 64 as shown in FIG. 11 as the sleeve 60 does not exist beyond the uppermost coil loop of the bottom section of the coil 8 but the flue flow must still traverse the apertures 20.

(29) In one embodiment, the coil includes a central axis and the guide system further includes a sleeve configured to surround the coil, the sleeve 60 disposed about the central axis of the coil, the sleeve including a plurality of top apertures 62 disposed in a manner to coincide with the top section of the coil and a plurality of bottom apertures 64 disposed in a manner to coincide with the bottom section of the coil and the flue flow 32 is urged from within the lumen of the coil to outside of the lumen of the coil at the top section of the coil through the plurality of top apertures 62 of the sleeve and the flue flow continues to enter the lumen of the guide system through the plurality of bottom apertures 64 of the sleeve and the plurality of apertures 20 of the guide system. In one embodiment, the coil includes a plurality of coil loops and a central axis, the guide system further includes at least one strip 66 configured to be disposed between the plurality of coil loops, the guide system further includes a sleeve 60 configured to surround the coil, the sleeve 60 disposed about the central axis of the coil 8, the sleeve 60 including a plurality of top apertures 62 disposed in a manner to coincide with the top section of the coil and a plurality of bottom apertures 64 disposed in a manner to coincide with the bottom section of the coil and the flue flow is urged from within the lumen of the coil to outside of the lumen of the coil at the top section of the coil through the plurality of top apertures 62 of the sleeve and the flue flow continues to enter the lumen of the guide system through the plurality of bottom apertures 64 of the sleeve through a space in which the bottom section of the coil is disposed, the space defined by the at least one strip 66, the sleeve 60 and the guide system 14 and through the plurality of apertures 20 of the guide system 14.

(30) The detailed description refers to the accompanying drawings that show, by way of illustration, specific aspects and embodiments in which the present disclosed embodiments may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice aspects of the present invention. Other embodiments may be utilized, and changes may be made without departing from the scope of the disclosed embodiments. The various embodiments can be combined with one or more other embodiments to form new embodiments. The detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, with the full scope of equivalents to which they may be entitled. It will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of embodiments of the present invention. It is to be understood that the above description is intended to be illustrative, and not restrictive, and that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Combinations of the above embodiments and other embodiments will be apparent to those of skill in the art upon studying the above description. The scope of the present disclosed embodiments includes any other applications in which embodiments of the above structures and fabrication methods are used. The scope of the embodiments should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.