Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
  • F28D21/0001—Recuperative heat exchangers
  • F28D21/0003—Recuperative heat exchangers the heat being recuperated from exhaust gases
  • F28D21/0005—Recuperative heat exchangers the heat being recuperated from exhaust gases for domestic or space-heating systems
  • F28D21/0007—Water heaters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D10/00—District heating systems
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D12/00—Other central heating systems
  • F24D12/02—Other central heating systems having more than one heat source
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D7/02—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being helically coiled
  • F28D7/024—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being helically coiled the conduits of only one medium being helically coiled tubes, the coils having a cylindrical configuration
• • 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
  • F28F1/08—Tubular elements crimped or corrugated in longitudinal section
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F27/00—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus
  • F28F27/02—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus for controlling the distribution of heat-exchange media between different channels
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/007—Auxiliary supports for elements
  • F28F9/013—Auxiliary supports for elements for tubes or tube-assemblies
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D2200/00—Heat sources or energy sources
  • F24D2200/16—Waste heat
  • F24D2200/18—Flue gas recuperation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F2250/00—Arrangements for modifying the flow of the heat exchange media, e.g. flow guiding means; Particular flow patterns
  • F28F2250/06—Derivation channels, e.g. bypass
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
  • Y02B30/17—District heating
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/14—Combined heat and power generation [CHP]

Definitions

• a heat exchanger combination with heat exchanger and method of manufacturing the heat exchanger
• the present invention relates to a heat exchanger for heat exchange between a first fluid and a second fluid and comprising a generally cylindrical casing with a first inlet and a first outlet for allowing said first fluid to flow through said casing in a generally axial direction, and at least one helical coil of a finned or corrugated tube arranged inside said casing.
• Heat exchangers of this type are known where the first fluid is forced to flow from inside the coil or coils outwards or vice versa.
• the transfer of heat from the first fluid to the second fluid in the coils is not very well controlled and therefore not as efficient as possible.
• first fluid for instance exhaust gas from a natural gas fired turbine, an internal combustion engine, an incinerator, a furnace, a burner or the like
• this object is obtained by providing a generally cylindrical fluid conduit inside said casing generally coaxial therewith so that an axially extending first tubular space is defined between said conduit and said casing, said conduit having a second inlet and a second outlet for allowing said first fluid to flow through said conduit in a generally axial direction, and said first tubular space having a third inlet and a third outlet for allowing said first fluid to flow through said first tubular space in a generally axial direction, the at least one helical coil of a finned or corrugated tube being arranged inside said first tubular space generally coaxial therewith and having a fourth inlet and a fourth outlet for allowing said second fluid to flow through said finned tube.
• the heat exchanger further comprises first adjustable throttle means for adjustably throttling said flow of said first fluid through said conduit and/or second adjustable throttle means for adjustably throttling said flow of said first fluid through said first tubular space.
• the flow of first fluid may by-pass the finned tube coils so that the heat transfer to the second fluid may be reduced according to the demand for heated second fluid.
• the pressure loss from the inlet of the casing to the outlet thereof may be reduced by by-passing the finned tube coils which is desirable during start up of for instance a gas fired turbine generating the first fluid in the form of exhaust gas from the gas combustion.
• said first throttle means comprise a first butterfly valve, preferably arranged adjacent said second inlet or said second outlet
• said second throttle means comprise a second butterfly valve, preferably arranged adjacent said third inlet or said third outlet.
• said first throttle means comprise a first butterfly valve, preferably arranged adjacent said second inlet or said second outlet
• said second throttle means comprise a ring having planar dimensions corresponding to the cross section of said first tubular space and being arranged for being displaced from a heating position wherein said flow of first fluid through said tubular space is substantially unhindered to a bypass position wherein said flow is substantially obstructed.
• the space requirements are reduced.
• said first and second throttle means comprise a fixedly arranged stationary plate with first and second apertures provided therein arranged such that said second and third inlets or outlets are obstructed by said plate such that the flow of first fluid through said conduit and said first tubular space takes place through said first and second apertures, respectively, in said stationary plate, and one or two movable plates with third and fourth apertures provided therein and arranged displaceable, preferably rotatably displaceable, from a bypass position overlying said stationary plate, wherein said third apertures coincide with said first apertures and said fourth apertures do not coincide with said second apertures, to a heating position overlying said stationary plate wherein said fourth apertures coincide with said second apertures and said third apertures do not coincide with said first apertures.
• This embodiment of the first and second throttle means requires a minimum of space and is particularly well suited for precise adjustment of the by-pass flow through the conduit relative to the heat transfer flow through the tubular space.
• the heat exchanger according to the invention further comprises preferably motorized actuating means for adjusting the throttling effect of said first and second throttle means, and said throttling means and said actuating means are preferably adapted such that substantially any rate of flow between a maximum and minimum rate of flow of said first fluid through said second inlet and said third inlet may be obtained. Said minimum rate is substantially equal to zero.
• any distribution of fluid flow between the by-pass conduit and the tubular space may obtained which allows simple and precise regulation of the output of the heat exchanger according to the requirements for heat transfer from the first fluid.
• substantially total by-pass no heat is transferred to the second fluid which is advantageous in case no heat transfer is needed to means exterior of the heat exchanger and therefore no temperature increase with consequent steam formation will take place in the finned coil or coils.
• the currently preferred embodiment of a heat exchanger comprises two or more of said helical coils arranged concentrically and such that mutually adjacent coils are radially spaced such that an axially extending second tubular space is provided between said mutually adjacent coils, and the outer surface of said conduit is spaced radially from the coil adjacent said surface such that an axially extending third tubular space is provided between said surface and said adjacent coil, the radial dimensions of said second and third tubular spaces being adapted so as to achieve a certain pressure loss for a given rate of flow of said first fluid through said first tubular space.
• the pressure loss from said first inlet to said first outlet for a given flow of first fluid may be kept at a minimum while not substantially reducing the efficiency of the heat exchanger.
• This is particularly of importance in connection with gas fired turbines being the origin of said first fluid because gas turbines are particularly sensitive to the back pressure at the exhaust outlet thereof.
• the mutually adjacent individual windings of a coil are mutually axially spaced such that a helically extending space is provided between said adjacent windings.
• any differential thermal expansion or contraction of the casing and/or conduit relative to the coils in the axial direction will be taken up by said helically extending space.
• third throttling means are provided in the tubes constituting the coils located radially inwards of the outermost coil for increasing the pressure loss through the tubes of said inner coils so as to compensate for the shorter length of said tubes relative to the length of the tubes of the outermost coil such that the rate of flow of said second fluid through the tubes of all the coils is substantially the same for a given uniform pressure in said second fluid at said fourth inlets.
• the heat transfer efficiency of each coil will be substantially the same without having to vary the diameter of the tubes of each coil to achieve this effect.
• said third throttling means are constituted by a reduction of the cross sectional area of the flow of said second fluid relative to the internal cross sectional area of said tubes, the heat exchanger preferably further comprising an inlet header tube and an outlet header tube in fluid communication with said fourth inlets and fourth outlets, respectively, of all said tubes through corresponding communication apertures in said header tubes, said reduction of flow cross sectional area being constituted by reduced size of said communication apertures in said inlet header tube and/or in said outlet header tube.
• each helical coil may advantageously comprise two or more helically wound finned tubes extending adjacent one another with the same pitch.
• the number of flow paths is increased which is advantageous in connection with the large volume expansion of the water in the coil tubes resulting from the steam generation.
• the present invention relates to a combination of a heat exchanger according to the invention and an exhaust gas generating combustion means such as a natural gas fired turbine, an internal combustion engine based on gasoline, diesel oil or natural gas, a furnace, a burner, an incinerator and the like, the combination comprising interconnection means for interconnecting an exhaust gas outlet of the combustion means with said second and third inlets of the heat exchanger such that said exhaust gas constitutes said first fluid.
• an exhaust gas generating combustion means such as a natural gas fired turbine, an internal combustion engine based on gasoline, diesel oil or natural gas, a furnace, a burner, an incinerator and the like
• the currently preferred embodiment of the combination according to the invention may further comprise heat exchanging means for heat exchange between said second fluid and a third fluid and/or the surroundings of said heat exchanging means, said heat exchanging means being in fluid communication with said fourth outlet, measuring means for measuring the rate of heat exchange of said heat exchanging means, signal output means for emitting a signal representing the result of a measurement carried out by said measuring means, and first control means for controlling the adjustment of said first and second throttle means and adapted for receiving said signal.
• the combination according to the invention further comprises second control means for controlling the adjustment of said first throttle means such that the throttling effect thereof is at a minimum during the start up phase of the combustion means.
• the present invention relates to a method of manufacturing a heat exchanger according to the invention and comprising the steps of providing a first length of finned or corrugated tube, providing a body having a substantially circular cylindrical surface, providing rotating means for causing relative rotation of said tube and said surface, arranging a lead portion of said tube abutting against said surface, and causing relative rotation of said surface and said lead portion such that said first length of tube is helically wound on said surface to form a first helical coil.
• a particularly simple, precise and inexpensive method of manufacturing a heat exchanger according to the invention is achieved.
• the method according to the invention preferably comprises the further steps of providing spacing means, attaching said spacing means to said first helical coil, providing a second length of finned or corrugated tube, arranging a lead portion of said second length of finned tube abutting against said spacing means, causing relative rotation of first helical coil and said lead portion of said second length of tube such that said second length of tube is helically wound on said spacing means to form a second helical coil radially spaced from said first helical coil.
• the method according to the invention preferably comprises the further steps of fixating said helical coil relative to said body, and subjecting said body and said coil to annealing heat treatment and/or fixating said second helical coil relative to said body and/or said first helical coil, and subjecting said body and said first and second coils to annealing heat treatment.
• fixating said helical coil relative to said body and subjecting said body and said coil to annealing heat treatment and/or fixating said second helical coil relative to said body and/or said first helical coil, and subjecting said body and said first and second coils to annealing heat treatment.
• Fig. 1 is an elevational partly sectional diagrammatic view of a first currently preferred embodiment of a heat exchanger according to the invention
• Figs. 2-3 are schematic plan views illustrating a fin configuration of the finned tubes according to the invention.
• Fig. 4 is a schematic bottom view of the embodiment of Fig. 1 .
• Fig. 5 is an elevational partly sectional diagrammatic view of a second currently preferred embodiment of a heat exchanger according to the invention.
• Fig. 6 is a schematic view of an inlet header tube for an embodiment of the heat exchanger according to the invention provided with four concentrically arranged finned tube coils,
• Fig. 7 is a broken away elevational view of a third embodiment of a heat exchanger according to the invention
• Fig. 8 is a diagrammatic enlarged scale view of a portion of the embodiment in Fig. 1 illustrating the spacing of the finned tubes of the coils
• Fig. 9 is a schematic elevational, broken away, partly sectional view of the top of the embodiment shown if Fig. 5 illustrating a first embodiment of throttle means according to the invention
• Fig. 10 is a schematic elevational, broken away, partly sectional view of the top of a fourth embodiment of a heat exchanger according to the invention illustrating a second embodiment of throttle means according to the invention
• Fig. 11 is a schematic top view of the embodiment of Fig. 10,
• Fig. 12 is a schematic elevational, cut away view illustrating a third embodiment of throttle means according to the invention.
• Fig. 13 is a schematic top view illustrating a fourth embodiment of throttle means according to the invention.
• Fig. 14 is a schematic, partly sectional, naval vessel and fastening means for the coils of the embodiment of Fig. 1 ,
• Fig. 15 is a schematic top view illustrating the method according to the invention of manufacturing the embodiment of Fig. 5, and
• Fig. 16 is a diagram illustrating one embodiment of control means according to the invention for adjusting the throttle means according to the invention.
• a heat exchanger 1 according to the invention comprises an outer cylindrical casing 2 provided with a flanged inlet 3 and a flanged outlet 4.
• An interior cylindrical casing or conduit 5 having an inlet 6 and an outlet 7 is arranged coaxially with the outer casing 2 thereby defining a tubular space 8 wherein two coils 9 and 10 of finned tubing are arranged.
• the finned tubing consists of a tube 11 provided with fins 12 arranged generally transversely to the axis of the tube 11.
• the finned tube coils 9 and 10 are arranged mutually concentric and coaxially with the outer and inner casings 2 and 5.
• a flanged outlet header tube 13 and a flanged inlet header tube 14 communicate with the interior of the tubes 11 of the coils 9 and 10 through apertures 15 and 16, respectively.
• a butterfly valve 17 (by-pass valve) is pivotably arranged on a shaft 18 at the outlet 7 of the conduit 5, a position wherein the valve 17 is in an intermediate position between fully closing the outlet 7 and fully opening said outlet 7 being shown with dotted lines at 17a.
• Semicircular rings 19 and 20 are arranged for abutting the rim of the butterfly valve 17 in the closed position thereof thereby ensuring a good closing function of the valve 17.
• the heat exchanger 1 is primarily intended for use in combination with a natural gas fired turbine for recuperating and utilizing the heat of the exhaust gases thereof, but may in principle be used in combination with any means producing a heated gas such as internal combustion engines, furnaces, burners, incinerators and the like.
• the butterfly by-pass valve 17 is in the closed position shown in full lines in Fig. 1 whereby all the exhaust gas from the gas turbine introduced into the inlet 3 flows through the tubular space 8 past the finned tube coils 9 and 10 as indicated by the full line arrows. Water to be heated is introduced into the coils 9 and 10 through inlet header 14 and is discharged through apertures 15 and 16 and outlet header 4 after having been heated by heat transmission from the exhaust gas through fins 12 to the tubes 11 and thereby to the water in said tubes.
• the heated water is transported to not shown exterior heat exchange means for transmitting some of the heat of the water to some other fluid or to the surroundings, typically radiators in a building heating system or a district heating system.
• the butterfly valve 17 is pivoted on shaft 18 so as to allow some or all the exhaust gas from the gas turbine to flow through the internal conduit 5 as indicated with dotted arrows thereby by-passing the tubular space 8 and the coils 9 and 10.
• the butterfly valve 7 can also be described as a throttling means and may be substituted by other throttling means as described in the following in connection with Figs. 9-13.
• a strip 12a of carbon steel is laterally cut to form tabs or fingers 12b that are bent transverse to the plane of the strip in alternating directions and thereafter welded onto the surface of the tube 11 in a spiral configuration by means of welding seam 12c.
• a very effective heat transfers from the hot exhaust gas to the fingers 12b and thereby to the tube 11 may be achieved.
• Other configurations with circular plate shaped fins or corrugations may also be employed instead of the serrated spirally wound fins shown in Figs. 2 and 3.
• the tubes 11 are welded to the upper header tube 14 around the apertures 15 and 16 thereof whereby the interior of the tubes 11 communicates with the interior of the header tube 14,
• the coils 9 and 10 are attached to and suspended from the outer casing 2 and the inner conduit 5 by means of a beam 22 welded to said casing and conduit.
• the beam 22 is welded to two rings 23 and 24 fitting tightly around the fins 12b of the coils 9 and 10.
• a similar attachment is carried out at the bottom of the heat exchanger adjacent the inlet header tube 13.
• the innermost coil 10 is spaced from the outermost coil 9 by a tubular space having a thickness or radial dimension t1 , while the innermost coil 10 is spaced from the outer surface of the conduit 5 by a tubular space having a thickness or radial dimension t3.
• the outermost coil 9 is not spaced from the inner surface of the outer casing 2, i.e. the coil 9 abuts the casing 2.
• the spacings t1 and t3 are chosen such that the loss of pressure through the tubular space 8 is maintained at a level acceptable for the optimal operation of the gas turbine (or other hot exhaust gas generating means) delivering exhaust gas to the heat exchanger 1.
• the heat exchange efficiency of the heat exchanger 1 is not substantially affected by the spacings t1 and t3.
• operational tests show that if a spacing were present between the outer casing 2 and the outermost coil 9, then the efficiency of the heat exchanger 1 would be considerably reduced.
• exhaust gas pressure drop The exhaust gas pressure drop or loss is very dependent on the exhaust gas velocity and the geometry of the heating surface of the coil windings. The velocity is dependent on the free gas flow cross sectional area (total area for the gas flow between the tubes and fins in a cross section).
• ⁇ p exhaust gas pressure drop [Pa]
• ⁇ pressure drop coefficient, dependent on geometry (fin shapes, tube diameter, inline/staggered configuration, number of windings etc)
• p Density of the gas at mean temperature between inlet 3 and outlet 4 [kg/m3]
• w exhaust gas velocity [m/s]
• the allowable exhaust gas pressure drop in heat exchangers and boilers after gas turbines (and engines as well) is quite limited.
• gas turbines it is extremely important to minimize the exhaust gas pressure drop as the power production on the turbine (and thus the efficiency of the turbine) is very dependent on the back pressure.
• the allowable exhaust gas pressure drop is preferably limited to be below 500 Pa (50 mm water column), giving very low exhaust gas velocities and thus large distance between the coils (alternatively more coils giving larger gas cross section area and larger diameter of the unit).
• the heat transfer coefficient should be as high as possible to minimize the heating surface area.
• the heat transfer coefficient is increased with higher exhaust gas velocities and more turbulent flow.
• the turbulence of the flow is very good, in general giving high heat transfer coefficient even for low exhaust gas velocities.
• Designing the heat exchanger according to the invention with the spacings t1 and t3 is also advantageous from a production point of view because it allows the coils to be inserted in the casing individually as compared with coils designed to abut one another or to be nested in one another that must be handled and inserted as a unit comprising several coils.
• a helically extending space is provided between adjacent windings of each coil 9 and 10, the thickness or axial dimension of said space being t2.
• This spacing t2 of the windings allows the casing 2 and/or the conduit 5 to thermally expand and contract axially relative to the coils 9 and 10 without causing unacceptable stresses as any differences in such expansion or contraction is taken up by variations of the spacing t2 between the windings of the coils.
• Insulation 100 mm covered with galvanized steel plate
• Flue gas outlet flange DN 450, DIN 86044
• Thickness of casing (inner 5 and outer 2): 5 mm • Weight of heat exchanger excl. water: 475 kg Weight of heat exchanger incl. water: 500 kg
• Tube material thickness 3.6 mm
• Thickness of fins 1 mm
• Tube pitch in gas direction 70 mm
• Free spacing t2 between fins on coil windings in gas direction 2 mm
• FIG. 5 an embodiment of a heat exchanger 31 according to the invention having three concentric coils 32-34 is shown with the same reference numbers being utilized for elements similar to elements in Fig. 1.
• the inner coils 33 and 34 (where the second fluid (typically water) have shorter flow paths than in the outermost coil 32) can transport more water than the outer coil 32.
• the water in the coils 33, 34 and 35 will then not be heated to the same temperature and will result in a skewed and reduced recuperation of the heat contained in the first fluid (for instance exhaust gas from a gas fired turbine).
• the flow rate through the coils be regulated so that best possible heat recuperation is obtained with best possible temperature distribution both in the water and in the exhaust gas. This is achieved by creating an extra pressure loss in the inner coils 33 and 34 relative to the outer coil 35 and each other.
• throttle or baffle means in the tubes or at the inlet or outlet thereof.
• this can be achieved by providing the outlet header tube 38 with apertures 35-37 and 40-43, respectively, having different diameters.
• the diameters of the individual apertures are determined based on the tube diameter and tube length in the individual coils of a heat exchanger. As an example of diameters for the four apertures shown in Fig. 6 for an inner diameter of 56 mm of all four coil tubes, aperture 40 is 56 mm, aperture 41 is 13 mm, aperture 42 is 11 mm and aperture 43 is 9 mm.
• Other throttle or baffle means well known in the art may also be used to achieve the different pressure loss coefficients for the individual coil tubes.
• the inner coil adjacent the inner conduit 5 comprises two parallel wound finned tubes 50 and 51 establishing two parallel flow paths for the second fluid (typically water) indicated by the arrows R1 and R2.
• the second fluid typically water
• This embodiment is intended for use for steam generation where it is necessary to take into consideration the large volume expansion of the mass inside the tubes (at the transition from liquid to vapour, water to steam) with corresponding increase in flow rate and velocity as well as pressure loss at the inner surface of the tubes. So as to provide sufficient inner flow cross sectional area in the tubes it will therefore often be necessary to use a larger tube diameter, a larger number of coils or provide for a larger number of flow paths in other ways.
• Figs 9-13 various embodiments of throttle means for throttling the flow of first fluid (typically exhaust gas) through the conduit 5 and the tubular space 8, respectively, are shown.
• first fluid typically exhaust gas
• the butterfly valve 17 cooperates with a ring 52 that is suspended in three steel wires 53 attached at equidistant points along the ring 52.
• the wires 53 extend over pulleys 54 to the shaft 18.
• the butterfly valve 17 is closed and does not allow any exhaust gas to flow through conduit 5 while the ring 52 is in its highest position in which it does not throttle the flow of exhaust gas through the tubular space 8.
• the butterfly valve 17a functions as a by-pass valve and allows unthrottled flow of exhaust gas through the conduit 5 while the ring 52a is in its full throttle position supported on tightening rings 55 thereby preventing flow of exhaust gas through the tubular space 8.
• the shaft 18 may be actuated manually, by an electric motor or a pneumatic or hydraulic mechanism.
• the wires are wound onto and off not shown pulleys arranged on the shaft 18 such that rotation of the shaft 18 for opening of the butterfly valve 17 automatically entails lowering of the ring 52 and vice versa.
• a very simple means for regulating the heat output of the heat exchanger 31 is thus provided.
• a temperature sensor and transmitter may be provided in the outlet header 38 for transmitting a signal to the not shown actuator (electric motor) for the shaft 18 so that if the temperature measured at the outlet header does not conform to the required temperature, then the shaft rotates in the corresponding direction to either open or shut the by-pass valve 17.
• the not shown actuator electric motor
• Many different regulating circuits are conceivable depending on the requirements of the end user and the configuration of the external heat consumption devices connected to the heat exchanger 31.
• Figs. 10 and 11 showing an elevational and top view, respectively, of a second embodiment of the first and second throttling means for the flow of exhaust gas through the internal conduit and the tubular space, respectively
• the internal conduit 5 is connected to a further conduit 56 having an outlet 57 in which a butterfly valve 58 is rotatably mounted on a shaft 59.
• the outlet 57 communicates with the outlet 4 of the casing 5.
• the butterfly valve 58 may rotate with the shaft 59 from the shown closed position wherein the outlet 57 is totally obstructed and an open position wherein flow of exhaust gas through outlet 57 is unhindered.
• the tubular space 8 communicates with a space 60 defined by an extension of the outer casing 2, said space communicating with the outlet 4 through an aperture 61 in a plate 62.
• a butterfly valve 63 is mounted in said aperture 61 on the shaft 59 such that rotation of the shaft 59 rotates the butterfly valve 63 from the shown fully open position in which flow of exhaust gas from the tubular space 8 through the space 60 and through the aperture 61 is unhindered to a fully closed position in which flow of exhaust gas through the aperture 61 is totally obstructed.
• the shaft 59 is connected to an electric motor 64 for being rotated in opposite directions so as to rotate the valves 58 and 63 between the two positions described above and to any intermediate position.
• FIG. 12 in this embodiment the butterfly valves 58 and 63 of the embodiment in Figs 10 and 11 have been substituted by a butterfly valve 65 and two butterfly valves 66, respectively, the operation of the valves 65 and 66 and the shaft 59 being the same as described in connection with the embodiment of Figs. 10 and 11.
• a stationary circular plate 70 is arranged horizontally in an embodiment of the heat exchanger similar to the one shown in Fig 1 or Fig. 4 (without the butterfly valve 17) over the outlet of the conduit 5 and the annular outlet of the tubular space 8.
• the plate 70 is provided with apertures 71 communicating with the interior of conduit 5 and apertures 72 communicating with the tubular space 8.
• a rotatably arranged circular plate 73 is arranged on top of plate 70 on a pivot 74.
• the plate 73 is provided with apertures 75 identical in shape and distribution to apertures 72 in plate 70 and with apertures 76 identical in shape and distribution to apertures 71 in plate 70.
• An electrical motor 77 is arranged for rotating the rotatable plate 73 in both directions.
• the lower plate 70 may instead be the rotatable one whereby the pressure from the exhaust gas will press the plate 70 against the stationary plate 73 and enhance the sealing effect of abutment of the plates 70 and 73 against each other. Sealing between the plates may also be achieved in many other ways obvious to those skilled in the art.
• Fig. 15 a method according to the invention of manufacturing a heat exchanger (the embodiment of Fig. 5) according to the invention is illustrated.
• a cylindrical body 80 is constituted by a steel plate 81 with a thickness of 10 mm, a steel rod 82 inserted between the free axially extending edges of the plate 81 , and not shown circumferentially extending tightening straps or wires for holding the plate 81 and rod 82 in the shown cylindrical configuration.
• the inner coil 34 is wound helically around the body or core 80, the leading end (not shown) and the trailing end 11 a of the pipe 11 of the coil 34 being attached to the body by means of brackets or rods 83 welded to said ends and to the body 80.
• the tightening straps mentioned above are located outside the area of the body 80 to be covered by the coil 34.
• Four cylindrical plates 84 having a quarter circle cross section and a thickness equal to the required radial dimension t1 (see Fig. 8) are arranged on the outer surface of coil 33 with rods 85 arranged between mutually adjacent axially extending edges of the plates 84.
• the plates 84 and rods 85 are held in place by not shown circumferentially extending tightening straps or wires.
• the rods 85 have an oval or elliptical cross section and are placed between the plates 84 such that the major cross sectional dimension of the oval or ellipse is tangential to the circular circumference of the plates 84.
• next coil 33 is wound helically around the plates 84 and rods 85 with the leading and trailing ends of the coil 33 being welded to one of the plates 84 by means of brackets or rods 83 in a manner very similar to the winding and attachment of the inner coil 34.
• the process is repeated for the next coil 32. If more coils than three are required, the process described above may be repeated for any such further coils.
• the unit comprising the body 80, the coils 32-34 and the plates 84 with rods 85 is thereafter subjected to annealing heat treatment for avoiding elastic diameter expansion of the coils and to remove potentially damaging stresses.
• a heat exchanger according to the invention is particularly well suited for use in a combination or system comprising a gas fired turbine (or an internal combustion engine utilizing natural gas as fuel).
• a gas fired turbine or an internal combustion engine utilizing natural gas as fuel.
• Such a system is furthermore particularly well suited for (but not in any way limited to) for use in a system for small scale combined production of electricity and heat, for instance for large buildings, hospitals, small district heating systems and the like.
• a system or combination according to the invention including a heat exchanger according to the invention, a gas fired turbine and external heat consuming devices is shown with the following characteristics:
• the system can comprise other exhaust gas generating devices, and the regulation of the heat exchanger's by-pass valve (and the heat exchanger's throttle valve for throttling fluid flow through the tubular space containing the finned tube coils) can be provided for in many different manners depending on the configuration of the end user's heat consuming devices.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Geometry (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

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• 2002
  • 2002-11-07 CA CA002466564A patent/CA2466564A1/en not_active Abandoned
  • 2002-11-07 CN CNA028222814A patent/CN1585884A/zh active Pending
  • 2002-11-07 EP EP02787427A patent/EP1454107A1/en not_active Withdrawn
  • 2002-11-07 WO PCT/DK2002/000748 patent/WO2003040641A1/en not_active Application Discontinuation
  • 2002-11-07 JP JP2003542853A patent/JP2005509125A/ja active Pending
  • 2002-11-07 BR BR0213998-7A patent/BR0213998A/pt not_active Application Discontinuation

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