The disclosed subject matter relates generally to baffles for heat exchangers, and more particularly, to removable baffles for insertion in flue tubes of water heaters.
Conventionally, water heaters are employed (e.g., installed in one or more buildings) to generate and maintain a readily usable source of hot water (e.g., to be used by a building's occupants). To generate the heat for heating the water, water heaters receive a source of energy, such as electricity or fuel such as oil or natural gas, which is consumed by a burner to heat the water. The burner creates hot exhaust gases, which may be vented through flue tubes passing through a water tank of the water heater. These flue tubes may include baffles designed to create a higher temperature gradient near the flue wall and to enhance the level of turbulence, thereby increasing the efficiency of the water heater.
There remains a need for improvements in heat exchanger baffles in terms of at least one of heat exchange performance, cost, and manufacturability.
The subject matter disclosed herein is directed to water heaters, baffles for water heaters, and methods for manufacturing such baffles.
In one example, a baffle includes a core, an outer wall, and a plurality of fins. The outer wall surrounds the core and defines at least one flow path between the outer wall and the core. The fins extend from the outer wall toward the core. Each of the plurality of fins has a serpentine shape.
In another example, a method for manufacturing a baffle includes extruding at least one portion of the baffle in one piece, the at least one portion of the baffle having an at least partially cylindrical outer wall and a plurality of fins extending inward from the outer wall, each of the plurality of fins having a serpentine shape.
In yet another example, a baffle includes a cylindrical core, an at least partially cylindrical outer wall, and a plurality of fins. The cylindrical core extends in an axial direction. The at least partially cylindrical outer wall surrounds the core and defines at least one flow path between the outer wall and the core. The fins extend from the outer wall to the core. Each of the plurality of fins has a serpentine shape and extends in a direction parallel to the axial direction. The outer wall and the plurality of fins are formed in one piece from extruded aluminum. An outer surface of the outer wall includes a plurality of indents in positions corresponding to the plurality of fins.
In still another example, a baffle includes a cylindrical core, an at least partially cylindrical outer wall, a plurality of first fins, and a plurality of second fins. The cylindrical core extends in an axial direction. The core has an at least partially serrated surface. The at least partially cylindrical outer wall surrounds the core and defines at least one flow path between the outer wall and the core. The outer wall has an at least partially serrated inner surface. The plurality of first fins extend from the outer wall to the core. The plurality of second fins extend from the outer wall and stop short of the core. Each of the plurality of first and second fins has a serpentine shape and extends in a direction parallel to the axial direction. The core, the outer wall, and the plurality of fins are formed in one piece from extruded aluminum. Each of the plurality of first fins has a thickened end segment where the fin contacts the core. Each of the plurality of first and second fins has a thickened base segment where the fin contacts the outer wall.
In yet another example, a water heating system includes a burner, a vent, at least one flue tube, and at least one baffle. The burner is configured to create products of combustion. The vent is configured to vent the products of combustion from the water heater. The at least one flue tube provides a flow path for the products of combustion from the burner to the vent. The at least one baffle is removably positioned within the at least one flue tube. The at least one baffle includes a core, an outer wall, and a plurality of fins. The outer wall surrounds the core and defines at least one flow path between the outer wall and the core. The fins extend from the outer wall toward the core. Each of the plurality of fins has a serpentine shape.
The following detailed description is best understood when read in connection with the accompanying drawings, with like elements having the same reference numerals. When a plurality of similar elements are present, a single reference numeral may be assigned to the plurality of similar elements with a small letter designation referring to specific elements. When referring to the elements collectively or to a non-specific one or more of the elements, the small letter designation may be dropped. This emphasizes that according to common practice, the various features of the drawings are not drawn to scale unless otherwise indicated. On the contrary, the dimensions of the various features may be expanded or reduced for clarity. Included in the drawings are the following figures:
Aspects of the disclosed subject matter relate to baffling in heat exchangers. The disclosed baffles may provide improvements in efficiency of heat exchangers. Such improvements may be created, for example, due to the creation of higher temperature gradients near flue walls, an increase in the level of turbulence of gasses flowing through flue tubes, an improved flow path through a heat exchanger, improved heat flow or transfer through the baffle material, improvements in latent heat transfer by enhancing the formation and drainage of water droplets/condensate for any condensing exhaust gases, or improvements in the cost and/or resources associated with producing, manufacturing, installing, or operating heat exchangers.
The subject matter disclosed herein is described primarily with respect to water heaters and water heating systems. However, it will be understood that the scope of this disclosure is not so limited. The subject matter of this disclosure is applicable to any type or variety of heat exchanger, including any heat exchanger designed to exchange heat between a flow of gas and a fluid (gas or liquid). In particular, this disclosure is not limited to devices for heating water (i.e. H2O). As used herein, the terms “water heater” and “water heating” are intended to encompass any system, device, or method adapted to generate and maintain a source of heated fluid.
The subject matter disclosed herein is described primarily with respect to separate inserts, which may be installed in existing compartments or tubes of a water heater. However, it will be understood that the scope of this disclosure is not so limited. The disclosed baffles may be formed as inserts which may be installed into an existing flue tube or heat exchanger, or may be manufactured as integral or unitary parts of a flue tube or heat exchanger. The separate baffle inserts described herein may provide particular advantages with respect to ease of manufacture and installation.
Referring now to the drawings,
Core 110 forms the center of baffle 100. Core 110 extends axially through baffle 100. Core 110 is positioned to extend along or adjacent the axial center of flue tube 10 when baffle 100 is inserted in flue tube 10. Core 110 may provide structural support for fins 150. Core 110 may likewise prevent shoot-through of hot gases through baffle 100, and thereby prevent poor heat transfer to the fins and consequently the flue tube walls.
Core 110 may have a size and shape dependent on the size and shape of the flue tube for which baffle 100 is intended. Core 110 may have a cylindrical shape, as shown in
Core 110 has a surface 112, as shown in
Outer wall 130 surrounds core 110. Outer wall 130 extends axially parallel to core 110. Outer wall 130 (in conjunction with core 110 and fins 150) defines at least one flow path for the passage of hot gases through flue tube 10. As shown in
Outer wall 130 may have a size and shape dependent on the size and shape of the flue tube for which baffle 100 is intended. As shown in
Outer wall 130 has an inner surface 132, as shown in
Outer wall 130 has an outer surface 134, as shown in
Fins 150 extend inwardly from outer wall 130 toward core 110. Fins 150 extend axially through baffle 100 in a direction parallel to the axial direction of core 110. Fins 150 (in conjunction with core 110 and outer wall 130) define at least one flow path for the passage of hot gases through flue tube 10. As shown in
Fins 150 each have a serpentine shape. As used herein, the term “serpentine shape” means a curving or undulating shape forming alternating convex peaks, such as round convex peaks 152, and concave valleys, such as round concave valleys 154, with those alternating peaks and valleys being mirrored on opposed sides of the fin (such that the location of a convex peak on one side of the fin corresponds to the location of a concave valley on the immediate opposite side of the fin). The serpentine design, compared to straight fins, provides a higher heat transfer surface area, a larger blocked cross section, and an enhanced level of turbulence for products of combustion flowing adjacent the fins. The serpentine design also promotes water droplet formation in any condensing exhaust gases/water heaters by lowering surface tension in the concave valleys.
As shown in
Fins 150 may all extend to and contact core 110, as shown in
Fins 150 have a base segment 156 where fins 150 extend from outer wall 130, and an end segment 158 where fins 150 contact core 110, as shown in
Core 110, outer wall 130, and fins 150 may be formed in one piece as a unitary structure, or may be formed as distinct pieces. As shown in
Core 210 forms the center of baffle 200. Core 210 extends axially through baffle 200. Core 210 is positioned to extend along or adjacent the axial center of flue tube 20 when baffle 200 is inserted in flue tube 20. Core 210 may provide structural support for fins 250. Core 210 may likewise prevent shoot-through of hot gases through baffle 200, and thereby prevent poor heat transfer to the fins and consequently the flue tube walls.
Core 210 may have a size and shape dependent on the size and shape of the flue tube for which baffle 200 is intended. Core 210 may have a cylindrical shape, as shown in
Core 210 has a surface 212, as shown in
Outer wall 230 surrounds core 210. Outer wall 230 extends axially parallel to core 210. Outer wall 230 (in conjunction with core 210 and fins 250) defines at least one flow path for the passage of hot gases through flue tube 20. As shown in
Outer wall 230 may have a size and shape dependent on the size and shape of the flue tube for which baffle 200 is intended. As shown in
Outer wall 230 has an inner surface 232, as shown in
Outer wall 230 has an outer surface 234, as shown in
Fins 250 extend inwardly from outer wall 230 toward core 210. Fins 250 extend axially through baffle 200 in a direction parallel to the axial direction of core 210. Fins 250 (in conjunction with core 210 and outer wall 230) define at least one flow path for the passage of hot gases through flue tube 20. As shown in
Fins 250 each have a serpentine shape, as that term is described earlier herein. Fins 250 include convex peaks 252 and round concave valleys 254. In fins 250, the convex peaks 252 may have a radius of curvature of from 0.03 in. to 0.15 in., and the concave valleys 254 may have a radius of curvature of from 0.005 in. to 0.025 in.
Fins 250 may all extend to and contact core 210, or may not extend to core 210, e.g., may terminate prior to contacting core 210. In one example, baffle 200 includes two sets of fins 250: fins 250a and fins 250b. Fins 250a extend to and contact core 210. Fins 250b terminate prior to contacting core 210, and do not contact core 210. As shown in
Fins 250 have a base segment 256 where fins 250 extend from outer wall 230, and an end segment 258 where fins 250 contact core 210 or terminate before contacting core 210, as shown in
Core 210, outer wall 230, and fins 250 may be formed in one piece as a unitary structure, or may be formed as distinct pieces. As shown in
Core 410 forms the center of baffle 400. Core 410 extends axially through baffle 400. Core 410 is positioned to extend along or adjacent the axial center of the flue tube when baffle 400 is inserted in the flue tube. Core 410 may provide structural support for fins 450. Core 410 may likewise prevent shoot-through of hot gases through baffle 400, and thereby prevent poor heat transfer to the fins and consequently the flue tube walls.
Core 410 may have a size and shape dependent on the size and shape of the flue tube for which baffle 400 is intended. Core 410 may have a cylindrical shape, as shown in
Core 410 has a surface 412, as shown in
Outer wall 430 surrounds core 410. Outer wall 430 extends axially parallel to core 410. Outer wall 430 (in conjunction with core 410 and fins 450) defines at least one flow path for the passage of hot gases through a flue tube. As shown in
Outer wall 430 may have a size and shape dependent on the size and shape of the flue tube for which baffle 400 is intended. As shown in
Outer wall 430 has an inner surface 432, as shown in
Outer wall 430 has an outer surface 434, as shown in
Fins 450 extend inwardly from outer wall 430 toward core 410. Fins 450 extend axially through baffle 400 in a direction parallel to the axial direction of core 410. Fins 450 (in conjunction with core 410 and outer wall 430) define at least one flow path for the passage of hot gases through the flue tube. As shown in
Fins 450 each have a serpentine shape, as that term is described earlier herein. Fins 450 may all extend to and contact core 410, as shown in
Fins 450 have a base segment where fins 450 extend from outer wall 430, and an end segment where fins 450 contact core 410, as shown in
In baffle 400, core 410, outer wall 430, and fins 450 are not formed in one piece. To the contrary, as shown in
The formation of baffle 400 in multiple baffle portions 400a and 400b may simplify installation of baffle 400 in a flue tube. In a particular example, as shown in
Baffle portions 400a and 400b each include respective engagement surfaces 470. The engagement surfaces 470 of baffle portion 400a are configured to mate with the engagement surfaces 470 of baffle portion 400b, in order to form a complete baffle 400. The curved profile of engagement surfaces 470 provides flexibility to mate the two baffle portions 400a and 400b without compromising the required seal between products the combustion within the baffle and the inner surface of the flue tube. This makes insertion possible even when the flue tubes are not perfectly circular, or when the flue tube inner diameter tolerance is large. In addition, this design enables the baffle 400 to remain functional in the case of thermal contraction and expansion without losing its contact to the inner wall of the flue tube.
In an example manufacturing method, baffle 100 and/or baffle 200 and/or baffle 400 may be manufactured by extrusion. Suitable extrusion apparatus for use in manufacturing baffles 100 or 200 or 400 are known, and may include the use of industry standard extrusion processes similar to those used for commercially available aluminum rods. Details regarding the manufacture of an example baffle are described below with respect to the components of baffles 100 or 200 or 400. However, it will be understood that the disclosed manufacturing method may be used to manufacture other baffles than those expressly described herein.
Baffle 100 and/or baffle 200 and/or baffle 400 may be manufactured by extruding at least one portion of baffle 100 and/or baffle 200 and/or baffle 400 in one piece. Baffle 100 and/or baffle 200 and/or baffle 400 may be formed from extruded aluminum to promote heat transfer through conduction. Other high thermal conductivity materials for extruding baffle 100 and/or baffle 200 and/or baffle 400 are known, and may be selected based on their suitability for extrusion and/or for the heat transfer properties.
For baffle 100, a portion of the baffle having outer wall 130 and fins 150 may be extruded in one piece. Core 110 may then be separately manufactured (e.g., extruded), and friction fit between ends of fins 150 to complete baffle 100. Such friction fit may occur shortly following extrusion or at a later time, e.g., during installation of baffle 100 in flue tube 10. For baffle 200, the entire baffle, including core 210, outer wall 230, and fins 250 (including fins 250a and fins 250b) may be extruded in one piece. For baffle 400, each baffle portion 400a and 400b may be extruded in one piece.
As set forth above, surfaces of baffle 100 and/or baffle 200 and/or baffle 400 may include serrations. Forming baffle 100 and/or baffle 200 and/or baffle 400 may promote formation of baffle 100 and/or baffle 200 and/or baffle 400 with serrations may improve the manufacturability or improve the extrusion process. Moreover, serrations increase heat transfer surface area and promote turbulence at the wall by disturbing momentum and heat transfer boundary layers, thereby improving efficiency of the baffle.
Burner 310 burns fuel to create products of combustion. Burner 310 may burn, for example, natural gas. Suitable burners for use as burner 310 are known, and other suitable fuels for burning by burner 310 are known.
Burner 310 may be provided in a combustion chamber 312 having one or more air inlets for receiving air for combustion from outside of the water heater, and one or more air outlets for allowing hot gasses including the products of combustion to exist combustion chamber 312. Burner 310 and/or combustion chamber 312 may or may not be provided with a fan or blower for drawing in air to promote combustion or forcing hot gasses out to promote heating or efficiency of water heating system 300.
Vent 320 vents products of combustion from water heating system 300. Vent 320 is configured to receive hot gasses containing the products of combustion from burner 310 and/or combustion chamber 312. In one example, vent 320 comprises a draft hood 322. Draft hood 322 may be configured to allow the hot gasses containing the products of combustion to mix with ambient air surrounding the water heater while being vented from the water heater. It will be understood that in other examples, vent 320 may not include a draft hood.
Flue tubes 330 provide a flow path through the water heater for the products of combustion to pass from burner 310 to vent 320. As shown in
Flue tubes 330 pass through a water storage tank 334. As such, the outer surface of flue tubes 330 is positioned in contact with water in water storage tank 334, to promote heat transfer between the hot gasses passing through flue tubes 330 and the water. Flue tubes 330 may be the same as, or include any of the features of, flue tubes 10 and 20 described herein.
At least one baffle 350 is positioned within at least one of flue tubes 330. Baffle(s) 350 may be removable positioned within flue tube(s) 330. Baffle(s) 350 may be the same as, or include any of the features of, baffle 100 and/or baffle 200 and/or baffle 400.
As shown in
Baffles 350 may be identical, or may have different arrangements of fins and/or flow paths, as desired. In one example, baffles 350 have identical arrangements of fins, but are angularly offset or rotated relative to one another, such that the fins of one baffle 350 are not axially aligned within flue tube 330 with the fins of another baffle 350. Baffles 350 may be rotated relative to one another by a predetermined amount, e.g., each baffle 350 may be offset by 45° relative to the baffle above or below. This angular offset or rotation may advantageously promote turbulent flow of hot gasses through flue tube 330 and between baffles 350, and thereby promote efficient and improved heat transfer between the hot gasses passing through flue tube 330 and water contained in water storage tank 334.
Examples of a baffle produced according to the disclosure herein have been prepared and tested for performance.
In the testing of
The hot gases flow to the top and exit from the flue tube. Energy/enthalpy content of combustion gases is calculated by measuring flow rate, temperature and gas composition. Energy transferred to water flow is calculated by measuring flow rate and inlet and outlet temperatures.
In the testing of
As shown in
As shown in
As shown in
As shown by the test results of
Although the invention is illustrated and described herein with reference to specific embodiments, the Invention Is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims, and any combination of any features of any of the embodiments herein may be made, without departing from the invention.
The present application claims priority to U.S. Patent Application No. 62/874,574, filed Jul. 16, 2019, entitled “HEAT EXCHANGER BAFFLES AND METHODS FOR MANUFACTURING THE SAME,” the contents of which are incorporated herein by reference in their entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US20/42096 | 7/15/2020 | WO |
Number | Date | Country | |
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62874574 | Jul 2019 | US |