Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B1/00—Methods of steam generation characterised by form of heating method
  • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
  • F22B1/021—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers with heating tubes in which flows a non-specified heating fluid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B37/00—Component parts or details of steam boilers
  • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
  • F22B37/10—Water tubes; Accessories therefor
  • F22B37/101—Tubes having fins or ribs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/42—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being both outside and inside the tubular element
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
  • F28F1/124—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and being formed of pins
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
  • F28F1/34—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending obliquely
  • F28F1/36—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending obliquely the means being helically wound fins or wire spirals

Definitions

• the present invention relates generally to a heat exchanger, and more specifically to a "direct-fired” or “indirect-fired” boiler for generating steam, hot water, hot oil, and hot molten metals.
• a "waste heat recovery" or indirect-fired boiler makes use of residual heat from an isolated themiodynamic process.
• radiation heat transfer is a less significant heat transfer mechanism for the indirect-fired boiler.
• the heat transfer medium is usually water and/or steam, due in large part to their widespread availability and substantial heat capacity.
• a conventional type of direct-fired boiler commonly called a "firetube” boiler, employs a fueled burner to generate heat. The burner is fired into a single main tube, called the firetube. This firetube absorbs the majority of the radiation emitted from the combustion process.
• convective/conductive couples drive heat transfer between the hot fluid and the heat transfer medium throughout the device.
• Conventional firetube boilers typically contain one to three additional banks of significantly smaller tubes, called passes.
• passes For example, a firetube boiler design that includes two banks of tubes in addition to the firetube is termed a "three-pass firetube boiler," elicited from the path of the hot fluid.
• the course of flow for the "three-pass firetube boiler” occurs after the fueled burner generates hot gas inside the firetube, which is then driven through a first bank of smaller tubes flowing opposite the firetube, and then diverted through a second bank of smaller tubes flowing parallel to the firetube.
• a channel, called the "turn-around pass,” is located between each pass, wherein the hot gas reverses direction.
• the hot gas cools while flowing through the tube passes of the firetube boiler by transferring energy to the heat transfer medium.
• all tube banks, less the "turn-around pass” are in heat transfer relationship with the heat transfer medium.
• an enlianced conduit replaces numerous conventional small tubes
• the enhanced conduit incorporates a plurality of fins, each of which extends through a wall of the conduit, i other embodiments, the enhanced conduit incorporates a plurality of tubes along its inner surface, through which a heat transfer medium flows.
• Both designs enhance the heat transfer relationship between the hot fluid and the heat transfer medium by providing a continuous heat transfer relationship with the heat transfer medium, increasing the surface area involved in the heat transfer relationship and enhancing convection/conduction couples.
• all of the tube banks of other devices in the art can be replaced by one continuous enhanced conduit.
• the heat transfer fluid flows through the enhanced conduit while the hot fluid flows along an outer surface of the enhanced conduit.
• the High-Efficiency Enhanced Boiler (HEEB) of the present invention offers improvements over conventional designs.
• a first improvement is a continuous heat transfer relation by surrounding the enhanced conduit with heat transfer medium.
• a second improvement is the possibility of substantial turndown ratios.
• a third improvement is the feasibility of manufacturing devices for applications requiring steam pressures in excess of 21.4 atmospheres absolute, whereas conventional firetube boilers have practical limitations.
• the HEEB is readily configurable to generate superheated steam. Therefore, a first objective of the present invention is to provide a High Efficiency Enhanced Boiler capable of generating superheated steam or steam/hot water output.
• a second objective of the present invention is to provide an effective method for direct-fire or indirect-fire heat transfer to a molten metal heat transfer medium.
• a third objective of the present invention is to provide a High Efficiency Enhanced Boiler for "waste heat recovery" or indirect-fired boiler applications.
• a fourth objective of the present invention is to provide a boiler with an enhanced conduit capable of removing heat from the burner flame by proximally located fins.
• a first aspect of the invention is directed toward a device for transferring heat from a fluid to a heat transfer medium
• a device for transferring heat from a fluid to a heat transfer medium comprising a vessel for containing the heat transfer medium, a conduit extending through a wall of the vessel, the conduit having a first surface in contact with the heat transfer medium and a second surface in contact with a fluid within the conduit, and a plurality of fins, each fin extending through a wall of the conduit, contacting the heat transfer medium and the fluid, wherein heat is transferred from the fluid to the heat transfer medium via the plurality of fins.
• a second aspect of the invention is directed toward a device for transferring heat from a fluid to a heat transfer medium
• a device for transferring heat from a fluid to a heat transfer medium comprising a vessel containing the heat transfer medium, a conduit extending through a wall of the vessel, the conduit having a first surface in contact with the heat transfer medium and a second surface in contact with a fluid within the conduit, and at least one tube, wherein the heat transfer medium flows within the tube and the fluid flows around the tube.
• a third aspect of the invention is directed toward a device for transferring heat from a fluid to a heat transfer medium
• a vessel containing the heat transfer medium, a first conduit extending through a wall of the vessel, the first conduit having a first surface in contact with the heat transfer medium and a second surface in contact with a fluid within the first conduit, a plurality of fins, each fin extending through a wall of the first conduit, wherein heat is transferred from the fluid to the heat transfer medium via the plurality of fins, and at least one tube, wherein the heat transfer medium flows within the tube and the fluid flows around the tube, and wherein heat is transfe ⁇ -ed from the fluid to the heat transfer medium via the tube.
• FIG. 1 shows a side-view of one embodiment of the invention.
• FIG. 2 shows a front- view of one embodiment of the invention.
• FIG. 3 shows a side elevational view of one embodiment of the invention.
• FIG. 4 shows a cross-sectional view of one embodiment of the invention.
• FIG. 5 shows a side elevational view of the device of FIG. 4.
• FIG. 6 shows a side elevational view of the device of FIG. 4.
• FIG. 7 shows a cross-sectional view of one embodiment of the invention.
• FIG. 8 shows a top-view of the device of FIG. 7.
• FIG. 9 shows a front-view of the device of FIG. 7.
• FIG. 10 shows a cross-sectional view of one embodiment of the invention.
• FIG. 11 shows a side elevational view of the device of FIG. 10.
• FIG. 12 shows a side elevational view of the device of FIG. 10.
• FIG. 13 shows a cross-sectional view of one embodiment of the invention.
• FIG. 14 shows a cross-sectional view of one embodiment of the invention.
• FIG. 15 shows a top view of the device of FIGS. 13 and 14.
• FIG. 16 shows a cross-sectional view of one embodiment of the invention.
• FIG. 17 shows a side elevational view of the device of FIG. 16.
• FIG. 18 shows a side elevational view of the device of FIG. 16.
• FIGS. 1 through 6 depict a boiler 1 of the present invention, which includes a vessel 10 for containing a heat transfer medium.
• vessel 10 is pressurized internally and designed according to American Society of Mechanical Engineers (ASME) codes for boilers and pressure vessels.
• ASME American Society of Mechanical Engineers
• the ASME codes are one of a few fabrication standards honored worldwide.
• internal design pressures for this class of vessel range from 1.1 to 21.4 atmospheres absolute, although there are vessels in existence that exceed pressures of 21.4 atmospheres absolute.
• the ASME codes and others restrict the materials and fabrication methods for vessels with internal design pressures over 2.0 atmospheres absolute. Therefore, only code recognized materials, such as, but not limited to, SA516 GR70, SA240 304, SA312 TP304, and SA106 B, are acceptable for fabrication of vessel 10.
• a feedwater inlet 30 is located near the bottom of vessel 10. Any steam having left sump 20 continues upstream to deliver the stored energy and then returns downstream as condensate to feedwater inlet 30, thus completing the cycle.
• This process is typical of a closed steam/water system, hi reality, system losses require that provisions be made to replenish the heat transfer medium (e.g., make-up water).
• deaerators and water treatments are meant to protect the system components from oxidation and chemical attack. However, since deaeraters and chemical treatments are known to those of ordinary skill in the art, further explanation will not be given.
• enhanced conduit 60 forms a non-communicating pressure boundary between a hot fluid contained within it and a heat transfer medium within vessel 10.
• enhanced conduit 60 is entirely in heat transfer relation with the hot fluid and the heat transfer medium.
• the hot fluid is hot air generated from a burner, although other fluids or liquids may be used.
• the embodiments of the invention are often depicted as steam boilers, necessitating that the heat transfer medium be water, other fluids or liquids are also allowable.
• the heat transfer medium may be any liquid, gas, or similar material with suitable heat transfer properties.
• enhanced conduit 60 extends horizontally near a central axis of vessel 10, as shown in FIGS. 4 through 6.
• a fuel-fired burner 70 generates heat and energy, which are forced into enhanced conduit 60.
• Burner fuel may include, for example, coal, distillate oil, natural gas, methanol, ethanol, propane, and liquefied petroleum gas.
• a forced draft subassembly (not shown) regulates the flow of gas to burner 70 so that the proper ratio of oxygen-to-fuel can be attained, and forces or drives the hot gas into enhanced conduit 60.
• enhanced conduit 60 is under the same pressure as vessel 10, except that the pressure is exerted on an internal surface of vessel 10 and an external surface of enhanced conduit 60.
• ASME code or other accepted design standard is invoked to comply with engineering requirements, hi general, with respect to the length of enhanced conduit 60, external pressure is more severe than internal pressure in terms of local stress.
• the cross- sectional geometry of enhanced conduit 60 is circular.
• a plurality of fins 80 extend intimately into the path of the hot fluid. Fins 80 establish a series of obstructions that force the hot fluid to assume a path around individual fins 80 in a manner that elicits turbulence, thereby enhancing heat transfer. Furthermore, a portion of each fin 80 extends through a wall of enhanced conduit 60 and contacts the heat transfer medium. Fins 80 thereby increase heat transfer through turbulent mixing of the hot fluid and by increasing the surface area exposed to the hot fluid and/or the heat transfer medium.
• Each fin 80 may be oriented through a wall of enhanced conduit 60 in any number of angles relative to the long and short axes of enhanced conduit 60. As such, fins 80 may be oriented to direct the flow of the hot fluid and/or the heat transfer medium along a particular path.
• Each fin 80 is fabricated from materials that demonstrate structural stability while providing good heat transfer characteristics. Possible fin 80 materials include, but are not limited to, generic steels, metals (including copper, molybdenum, etc.), ceramics, refractory materials, and engineered composites.
• a largely material-dependent objective of the present invention is the ability to extract heat by placing fins 80 in close proximity to the flame of burner 70.
• a fin configuration capable of meeting this objective comprises a cylindrical generic steel body fitted with a spherical molybdenum tip.
• cylindrical-shaped fins 80 are shown.
• other fin shapes or combinations of shapes are possible and considered to be within the scope of the present invention.
• Such shapes include, for example, square, elliptical, aerodynamic, rectangular, and spherical.
• such fins may be constructed with through holes, with threaded holes, with blind holes, and may be tapered or threaded.
• the fin shape may be cylindrical at one end, tapered in the middle, and rectangular with blind holes toward its opposite end.
• Each fin 80 may be mechanically fastened to enhanced conduit 60 in an ASME code or other acceptable method, forming a pressure-rated joint.
• the heat transfer medium is water/steam, although molten metal (heat transfer salt) and hot oil systems are possible. As suggested earlier, widespread availability and substantial heat capacity are factors favoring water/steam as the most common heat transfer medium.
• vessel 10 around the outside surface of enhanced conduit 60, is filled with the heat transfer medium (e.g., water).
• Demand for steam signals burner 70 to ignite fuel into a combustible flame. The flame is directed at hot fluid inlet 40 of enhanced conduit 60, whereby heat is drawn off by fins 80 located near the outer flame boundary.
• Fins 80 extract substantial energy from the flame by radiation/conduction/convection heat transfer to the heat transfer medium over the length of the flame. At the extreme boundary of combustion, where the flame ceases to exist, fins 80 remove heat from the hot fluid stream by convection/conduction couples. Additionally, the portion of each fin 80 extending within enhanced conduit 60 causes turbulence in the hot fluid stream, accelerating convection heat transfer, while the portion of each fin 80 extending outside enhanced conduit 60 provides more surface area for convective heat transfer to occur. More particularly, a balanced energy flow exists in the region of each fin 80. The exhausted hot gas leaves enhanced conduit 60 through the flue outlet 50 on route to the stack (not shown).
• a direct-fired 3-pass 30-horsepower boiler 100 is shown, fabricated in accordance with the present design criteria for a pressure of 10 atmospheres and requiring a one million BTU (British thermal units) natural gas burner.
• Cylindrical vessel 110 has dimensions of 42-inches O.D. wide by 60-inches O.D.
• Hot fluid enters boiler 100 through hot fluid inlet 140, passes through enhanced conduit 160, and exits through flue outlet 150. Condensate returns to boiler 100 through feedwater inlet 130.
• the temperature of the exhausted flue gas is approximately 230° C. The thermal efficiency of such a design is increased, in part, due to the fact that "turn-around passes" are maintained in heat transfer relationship with the heat transfer medium within the boiler.
• EXAMPLE 2 Referring now to FIGS. 13-18, a direct-fired boiler 200 is shown with a coiled enhanced conduit 260.
• the long axis of cylindrical vessel 210 is oriented vertically, rather than horizontally as in Example 1.
• enhanced conduit 260 is coiled within vessel 210, completing a total of three revolutions.
• Hot fluid enters boiler 200 through hot fluid inlet 240, passes through enhanced conduit 260, and exits through flue outlet 250.
• enhanced conduit 260 contains a plurality of fins 280 located around its circumference and along its length. Fins 280 may be fastened to enhanced conduit 260 by any of a number of means described above.
• EXAMPLE 3 Referring to FIGS. 19-21, a 4-pass conduit 360 is shown. Unlike earlier-described embodiments, wherein a heat transfer medium sits within a vessel, the depicted embodiment incorporates a housing 360A around the apparatus 360. Housing 360A directs a heat transfer medium along an outer surface of a pass 362, 364, 366, 368 as the hot fluid is directed along an inner surface of the same pass. In some embodiments, such as that shown in FIG.
• the apparatus has a "reverse flow,” wherein as the hot fluid enters first pass 362 (often a firetube), the heat transfer medium enters through a heat transfer medium inlet 368B at a distal end of the fourth pass housing 368A, flows in a direction substantially opposite that of the hot fluid, and exits through a heat transfer medium outlet 362B at a proximal end of the first pass housing 362A.
• first pass 362 often a firetube
• the heat transfer medium enters through a heat transfer medium inlet 368B at a distal end of the fourth pass housing 368A, flows in a direction substantially opposite that of the hot fluid, and exits through a heat transfer medium outlet 362B at a proximal end of the first pass housing 362A.
• three of the four passes 362, 364, 366 are enhanced, each containing a plurality of fins 380 extending through a wall of the pass.
• one or more enhanced pass 362, 364, 366 may contain a helical member 3
• helical member 390 contacts or resides 1 close to an inner surface of each enhanced pass housing 362A, 364A, 366A of apparatus housing 360 A and directs the heat transfer medium along the surface of the pass 362, 364, 366, effectively increasing contact between the pass and the heat transfer medium. Accordingly, in order to increase contact between fins 380 and the heat transfer medium, helical member 390 preferably lies parallel to the pattern of fins 380. Such an an-angement effectively creates channels between the surface of a pass 362, 364, 366 and a pass housing 362A, 364A, 366A, in which are situated a plurality of fins 380.
• Each pass 362, 364, 366, 368 is connected to another by a tum-around pass 363, 365, 367 which substantially reverses the direction of flow of the fluid within enhanced conduit 360.
• the fluid within enhanced conduit 360 initially flows through first pass 362 in direction A.
• first turn-around pass 363, the fluid substantially reverses direction, entering second pass 364 in direction B.
• second turn-around pass 365 the fluid again substantially reverses direction, entering third pass 366 in direction C.
• the fluid passes through third turn-around pass 367 and enters a non-enhanced pass 368 in direction D before flowing through flue outlet 350.
• FIGS. 21 shows a side cross-sectional view of the apparatus in order to depict the obstructions within each enhanced pass 364, 366 created by the interior projections of fins 380. Also depicted are the channels created between helical member 390 and enhanced pass housings 364A, 366 A. As depicted, only passes 362, 364, 366 contain fins 380 and, optionally, helical member 390. However, it should be recognized that turn-around passes 363, 365, 367 may be enhanced with fins 380 and/or helical member 390 in addition to or instead of passes 362, 364, 366.
• EXAMPLE 4 Referring to FIGS. 22-24, a modified 4-pass enhanced conduit 460 is shown.
• modified enhanced conduit 460 includes a fourth pass 468 comprised of a plurality of tubes 494.
• the plurality of tubes 494 is preferably arranged in a circular pattern, as depicted most clearly in FIG. 24, although other shapes are allowable.
• a plurality of tubes 494 is depicted, a single tube is also within the scope of the invention.
• Heat transfer medium enters an opening 498 in an end of each tube 494 and flows through tube 494, increasing the heat transfer from the hot fluid within fourth pass 468 to the heat transfer medium.
• baffles 496, 497 may be placed along the length of the plurality of tubes 494. Such baffles may be outer baffles 496, located around tubes 494, or inner baffles 497, located within the plurality of tubes 494.
• Outer baffles 496 are preferably ring shaped so as to fit around a circular arrangement of the plurality of tubes 494, although other shapes are allowable. Outer baffles 496 preferably contact or reside close to an inner surface of fourth pass housing 468A. Inner baffles are preferably disc shaped so as to fit within a circular arrangement of the plurality of tubes 494, although other shapes are allowable. Outer baffles 496 and inner baffles 497 disrupt the flow of the hot fluid within pass 468.
• Inner baffles 497 force the hot fluid outside the plurality of tubes 494 to a location between the plurality of tubes 494 and fourth pass housing 468A, while outer baffles 496 force the hot fluid in the opposite direction, i.e., into the center of the plurality of tubes 494. This disruption of the flow of the hot fluid increases heat transfer from the hot fluid to the heat transfer medium.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Geometry (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Fluidized-Bed Combustion And Resonant Combustion (AREA)

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• 2004
  • 2004-08-27 WO PCT/US2004/027812 patent/WO2005021122A2/en not_active Ceased
  • 2004-08-27 EP EP04782311A patent/EP1658462B1/de not_active Expired - Lifetime
  • 2004-08-27 AT AT04782311T patent/ATE528585T1/de not_active IP Right Cessation
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