Abstract:
An apparatus and method for fabricating an externally finned tubular heat exchanger assembly comprising two concentric thin walled tubular members defining therebetween an intermediate inner annular fluid flow channel, and positionally fixed therewithin an internal turbulizer strip extending longitudinally in a helical spiral. The tubulizer strip is embossed with corrugations prior to installation into the intermediate inner annular fluid flow channel. The corrugated strip is helically spiraled with sequential bridge gap spaces between adjacent serial turns wherein the corrugations form a series of triangular cross-sectional fluid flow passageways. Turbulizer corrugation expansion, after insertion into the inner intermediate annular fluid flow channel, mechanically anchors the corrugated turbulizer strip to the second inner concentric tubular member that has an end groove to provide engagement connection. The turbulizer is utilized to vary conductance and thus control fluid flow through the tubular inner channel of the second concentric tubular member. External fins are attached to the exterior circumferential surface of the first outer concentric tubular subassembly member to further enhance heat exchange.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to the field of heat exchangers, and more particularly to finned concentric tubular member heat exchangers.  
       BACKGROUND OF THE INVENTION  
       [0002]     The prior art relates to heat exchangers formed by finned concentric thin walled tubular members defining an intermediate inner annular fluid flow channel therebetween containing a corrugated, helical spirally formed turbulizer strip initially pre-assembled in a prestressed coiled condition and inserted longitudinally into the intermediate inner annular fluid flow channel formed between the two concentric thin walled tubular members.  
         [0003]     While concentric tubular thin walled heat exchanger assemblies are well known in the field and generally provide efficient and effective heat exchange between the fluid flow channel through the center of the concentric inner tubular member and that of a secondary fluid flow confined in the intermediate inner annular fluid flow channel between the paired tubular members, or between a fluid confined between the two paired tubular members and a fluid flow external to the outer tubular member, it has been determined that the heat transfer can be enhanced by improving the heat exchanger flow characteristics within the intermediate inner annular fluid flow channel by providing therein a helical spirally formed, corrugated turbulizer strip anchored to the second inner concentric thin walled tubular member to vary inner fluid flow conductance.  
         [0004]     This turbulizer structure is pre-fabricated during heat exchanger assembly by first applying a predetermined compressive force to the helical, spirally formed turbulizer corrugated strip member so that the turbulizer member is compressed prior to insertion, and then inserted into the fixed confinement within the intermediate inner annular fluid flow channel under the initial pre-stressed compressive force. The turbulizer peaks and valleys then expand to improve contact with the surrounding circumferential surfaces to enhance the efficiency of the heat exchanger. Improvements of the concentric tubular design of pre-existing heat exchangers is desired, as shown in the herein disclosed, invention, to achieve improved heat transfer and heat exchanger versatility.  
       SUMMARY  
       [0005]     An improved finned tubular heat exchanger assembly comprises an externally finned subassembly in combination with concentrically spaced-apart, thin walled tubular member subassemblies having therebetween an intermediate inner annular fluid flow channel containing an inner turbulizer subassembly. The first outer concentric thin wall tubular member subassembly has a larger inside circumference than the second inner concentric thin walled tubular member subassembly with a smaller outer circumference. The intermediate inner annular fluid flow channel, formed between the heat exchanger first and second concentric thin walled tubular members, defines the sidewalls of the intermediate inner annular fluid flow channel which is coincident with portions of the internal circumferential flow area of the first outer concentric thin walled tubular member subassembly.  
         [0006]     The finned tubular heat exchanger assembly has contained therewithin, along its internal longitudinal axis, at least one intermediate inner annular fluid flow channel. A helical, spiral uniformly wound, corrugated turbulizer strip is concentrically secured within the intermediate inner annular fluid flow channel and is positioned in the form of a helical space-gapped spiral that is longitudinally fixed axially and radially to the second concentric thin walled tubular member that defines the smaller circumferential internal sidewall of the intermediate inner annular fluid flow channel to thermally enhance heat transfer by interconnecting together both the inner circumferential area surface of the outer concentric thin walled tubular member and the outer circumferential area of the smaller second inner concentric thin walled tubular member subassembly.  
         [0007]     In addition to imparting good thermal conduction contact with the second concentric thin walled tubular member surface, the turbulizer strip subassembly is structurally designed and positioned to vary the internal cross-sectional flow area of the second concentric thin walled tubular subassembly member and provides additional control of inner concentric tubular fluid flow through the heat exchanger.  
         [0008]     The spiral turbulizer strip subassembly has corrugations with triangular cross-sectional areas and is constructed from a heat conductive material formed in a predetermined configuration to produce turbulization mixing of the fluid flow passing along and through the longitudinal triangular corrugations of the turbulizer strip subassembly. Fluid flow is confined in the heat exchanger between the intermediate inner annular fluid flow channel sidewalls to generate desired fluid turbulization as the fluid flows through the intermediate inner annular fluid flow channel formed between the inner circumferential surface of the first outer concentric thin walled tubular member and the outer circumferential surface of the second inner concentric thin walled tubular member, and also along the surfaces of the helical spiraled corrugated turbulizer strip, thereby enhancing fluid heat transfer and increasing thermal efficiency of the heat exchanger.  
         [0009]     The turbulizer strip corrugated cross-section triangular shaped longitudinal channels are smooth surfaced to reduce resistance to flow through the channels, and the fluid flow entering each corrugation passageway entrance is directed to and across the turbulizer spiral bridge space-gap to cause the downstream flow exiting from each proceeding corrugation flow channel to cross-mix and impinge upon and enter opposing passageway edges after exiting each succeeding corrugation, then promoting cross mixing across the turbulizer spiral gap before entering each succeeding series of downstream longitudinal corrugations.  
         [0010]     The corrugated turbulizer strip of the present invention extends spirally within the intermediate inner annular fluid flow channel, the corrugations having ridge peaked apexes and valley bottom bases, defining flattened tubular contact areas adjacent to the intermediate inner annular fluid flow channel side wall lines of contact between the corrugation sidewalls and the peripheries of the first outer concentric thin walled tubular member inner circumference and the second concentric thin walled tubular member outer circumference that collectively define sidewall boundaries of the intermediate inner annular fluid flow channel.  
         [0011]     The corrugated strip turbulizer directs the fluid flow leaving a first preceding triangular corrugation to axially flow across the spiral bridge space-gap formed between succeeding subsequent triangular longitudinal corrugations, promoting cross-mixing of fluid flow streams exiting preceding spiral corrugation passageways and then crossing the bridge space-gap separation areas between each of the succeeding spiral corrugated turbulizer flow passageways.  
         [0012]     The fluid flow conductance through the heat exchanger is varied by preselecting the desired second inner concentric tubular member cross-sectional area to produce the desired dynamic flow characteristics required for satisfying the heat transfer requirements of a specific fluid heat source. By varying the internal cross-sectional area of the second inner concentric thin walled tubular subassembly, such as by the turbulizer anchor end, crimping, or by other means reducing the internal diameter of the second concentric thin walled tubular member. Thus resistance to fluid flow resulting from cross-sectional flow area restriction is varied by the turbulizer anchor connection configuration.  
         [0013]     The finned tubular heat exchanger is thus fabricated by concentrically spacing apart two concentric tubular members to define an intermediate inner annular fluid flow channel chamber to place therewithin a turbulizer strip of corrugated sheet metal to extend longitudinally and spirally within the intermediate inner annular fluid flow channel. Adjacent spiral turns of the corrugated spirally formed strip are bridge gap-spaced apart from each other to provide a parallel series of individual longitudinal triangular passageways to define the triangular cross-section channel discharge exits discharging fluid flow between the side edges of each series of adjacent corrugated spiral turn produced parallel passageways. When fluid discharge from each preceding triangular corrugation channel discharges fluid flow across the corrugation spiral turbulizer bridge space-gap, that fluid flow is also directed into the triangular entrance passageways so that the fluid flow enters each succeeding turbulizer corrugated passageway and promotes efficient heat transfer.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The preferred exemplary embodiment of the invention will hereinafter be described in conjunction with the appended drawings.  
         [0015]      FIG. 1  is an axial cross-sectional view of one embodiment of the present invention.  
         [0016]      FIG. 2  is a cross-sectional end view of a portion of the embodiment of  FIG. 1 .  
         [0017]      FIG. 3  is a plan view of a corrugated turbulizer subassembly member after corrugation.  
         [0018]      FIG. 4  is a cross-sectional end view of the turbulizer subassembly member along line  4 - 4  of  FIG. 3 .  
         [0019]      FIG. 5  is a cross-sectional side view of a portion of the turbulizer member after insertion.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     Referring to  FIGS. 1, 2 ,  4 , and  5  of the drawings, there is shown an improved finned concentric thin walled tubular member heat exchanger assembly  10  comprised of an external finned subassembly, a first outer concentric thin walled tubular subassembly member  20  having a first larger inside circumference  25 , a second inner concentric thin walled tubular subassembly member  40  having a second smaller outside circumference  45 , and having formed therebetween the two tubular members a longitudinal intermediate inner annular flow channel axial region  60 , within which is positioned an internal turbulizer subassembly member  70  being formed as a corrugated strip with triangular cross-sectional area passageways  72  that extend spiral axially within the intermediate inner annular flow channel axial region member  60  between the first outer concentric thin walled tubular subassembly member  20  having a larger inside circumference  25  and the second inner concentric thin walled tubular subassembly member  40  having the smaller outside diameter  45 . The first outer concentric thin walled tubular subassembly member  20  has externally attached thereto a plurality of longitudinally spaced transverse exterior rippled fins  102  forming an external rectangular fin subassembly  100  that radiate or absorb heat from surrounding areas to provide efficient heat transfer to the heat exchanger fluid flowing through the axial intermediate inner annular flow channel axial region  60  defined between the first outer concentric thin walled tubular subassembly member  20  and the second inner concentric thin walled tubular subassembly member  40 .  
         [0021]     As shown in  FIGS. 4 and 5 , the internal turbulizer subassembly member  70  is preformed prior to placement in the longitudinal intermediate inner annular flow channel axial region  60  by pressing it onto the second inner concentric thin walled tubular subassembly member  40 , or otherwise compressed for helical insertion between the first outer concentric thin walled tubular subassembly member  20  and second inner concentric thin walled tubular subassembly member  40 , within the intermediate inner annular flow channel axial region member  60 .  
         [0022]     In one method of fabrication, the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45  may be expanded slightly so as to compress the turbulizer assembly corrugations between the outer periphery of the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45  and the inner periphery of the first outer concentric thin walled tubular subassembly member  20  having a larger inside circumference  25 . Mechanical anchor locking of the internal turbulizer subassembly member  70  positionally between the first outer concentric thin walled tubular subassembly member  20  having a larger inside circumference  25  and the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45  is achieved by mechanically forcing a mandrel of slightly larger circumference than the external circumference of the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45  through the center of the internal turbulizer subassembly member  70  to expand the turbulizer slightly, and thus mechanically force the corrugated peak apex ridges  92  and the corrugated valley base bottoms  94  of the individual corrugated strip triangular cross section peak apex ridges  92  and valley base bottoms  94  to compress into prestressed contact with the respective peripheries of the first outer concentric thin walled tubular subassembly member  20 , and the second inner concentric thin walled tubular subassembly member  40 . This compressive force is sufficient to assure metal-to-metal contact for effective heat transfer contact between the first outer concentric thin walled tubular subassembly member  20 , and the second inner concentric thin walled tubular subassembly member  40 , and the internal turbulizer subassembly member  70 . The internal turbulizer subassembly member  70  interconnects the first outer concentric thin walled tubular subassembly member  20 , and the second inner concentric thin walled tubular subassembly member  40  to produce a longitudinal fluid flow path adjacent to the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45 , and the opposing adjacent first outer concentric thin walled tubular subassembly member  20 . Furthermore, in spiral winding the internal turbulizer subassembly member  70  into a helical configuration around the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45 , in accordance with U.S. Pat. No. 3,197,975 an open spiral gap space  78 , is formed providing a series of gapped non-turbulizer sections in the second inner concentric thin walled tubular subassembly member  40 , formed between adjacent helical turns of the helical spiraled turbulizer subassembly. There is thus defined an open-gapped helical spiral internal fluid flow turbulizer longitudinal passageways  72 , as shown in  FIG. 2 , into which each longitudinal passageway series has a periodically open spiral gap space  78 . The longitudinal passageways are thus interrupted by the spiral gap space  78  periodically by the spiral passageway  76 -bridge spiral gap space  78 . These minimize spiral gap space  78  resistance to fluid flow through intermediate inner annular flow channel axial region member  60  and provides for the efficient transfer of heat to and from the fluid passing through the intermediate inner annular flow channel axial region member  60 , as confined by the respective sidewalls of the first outer concentric thin walled tubular subassembly member  20 , and second inner concentric thin walled tubular subassembly member  40   
         [0023]     It has been determined that the fluid flow within the intermediate inner annular flow channel axial region member  60  forms a non-circulating skin film of fluid on the turbulizer surfaces at the edges of the internal turbulizer subassembly member  70  that becomes progressively thicker extending towards maximum circulation at the circumference edge of the gapped spiral turbulizer member, and this condition acts as a heat insulator causing resistance to heat transfer and reducing the efficiency of the heat exchanger system. An advantage of the helical internal fin heat exchanger of U.S. Pat. No. 3,197,975 is that the longitudinal dimensions of each of the individual passageway surfaces of the corrugated turbulizer strip subassembly members prevent the formation of a non-circulating fluid flow film sufficient to interfere materially with the proper transfer of heat between portions of the fluid flow traversing longitudinal intermediate inner annular flow channel axial region member  60 . A more effective heat exchange process occurs by reducing surface area portions of the exterior metallic fin strips by prestress fabricating the internal turbulizer subassembly member  70 , and then inserting it into the intermediate inner annular flow channel axial region member  60  improve the heat exchange properties of the first outer concentric thin walled tubular subassembly member  20 , and second inner concentric thin walled tubular subassembly member  40  employing the internal turbulizer subassembly member  70 .  
         [0024]     In accordance with the present invention the heat exchange fluid causes flow cross mixing by the triangular corrugation longitudinal channel passageways. As mentioned previously, the heat exchanger, width, length, thickness, and the space-gaps between the edges of the helical strip that define the spiral or helical flow path for the fluid flow confined between the first outer concentric thin walled tubular subassembly member  20  and second inner concentric thin walled tubular subassembly member  40 , passes across the spiral gap space  78  in the turbulizer longitudinal passageways  72  defined by the corrugated strip triangular cross section  74  can, by design, substantially vary the effect of the tubulizer anchored end connection  79  of the second inner concentric thin walled tubular subassembly member  40  by varying the quantity of fluid flow passing through the second inner concentric thin walled tubular subassembly member  40 .  
         [0025]     A finned tubular heat exchanger assembly member  10  can thus be constructed by the selective fabrication of the first outer concentric thin walled tubular subassembly member  20 , and second inner concentric thin walled tubular subassembly member  40 . When the first outer concentric thin walled tubular subassembly member  20 , and second inner concentric thin walled tubular subassembly member  40  are assembled together, the second inner concentric thin walled tubular subassembly member  40  is longitudinally positionally centrally within the first outer concentric thin walled tubular subassembly member  20 , whereby the first outer concentric thin walled tubular subassembly member  20 , and said second inner concentric thin walled tubular subassembly member  40  concentrically define the outer surface circumference and inner and outer circumference of the intermediate inner annular flow channel axial region member  60 .  
         [0026]     An internal turbulizer subassembly member  70  is embossed in a manner to provide a lateral triangular cross-sectional area to be inserted within the intermediate inner annular flow channel axial region member  60  to produce therein turbulizer longitudinal passageways  72 . The thus formed internal turbulizer subassembly member  70  is then end anchored to the second inner concentric thin walled tubular subassembly member  40  to anchor the internal turbulizer subassembly member  70 . The internal turbulizer subassembly member  70  is fabricated around the second inner concentric thin walled tubular subassembly member  40  initially with a predetermined compressive force to first contract, and then after insertion, expand to maximize surface contact with the first outer concentric thin walled tubular subassembly member  20 , and said second inner concentric thin walled tubular subassembly member  40 . The internal turbulizer subassembly member  70 , when end anchored to the second inner concentric thin walled tubular subassembly member  40 , produces a turbulizer end anchor connection  80  configuration designed to vary the cross-sectional flow area of the internal circumference of the second inner concentric thin walled tubular subassembly member  40  and the intermediate inner annular flow channel axial region member  60 .  
         [0027]     An anchor end connection slot  82  is machined in the second inner concentric thin walled tubular subassembly member  40  to connect with the anchor end connection tail structure  84 .  
         [0028]     The anchor end connection tail structure  84  protruding through the thin side walled of the second inner concentric thin walled tubular subassembly member  40  having a smaller outside circumference  45 . This turbulizer anchor end connection  79  may limit fluid flow conductance through the second tubular subassembly inner flow channel  27 , thereby by its design providing fluid flow control of the finned tubular heat exchanger assembly  10 .  
         [0029]     One embodiment of the finned tubular heat exchanger assembly member  10  has an internal turbulizer subassembly member  70  positioned in the intermediate inner annular flow channel axial region member  60 , and is constructed with a uniform sided, truncated triangular cross-sectional area having a rounded apex cross-section.  
         [0030]     The heat exchanger has a helically formed turbulizer that is uniform and sequentially gap interrupted passageway and external fins are formed radially with surface, semi-circular uniform corrugations to improve heat transfer by increasing the external surface area.  
         [0031]     The finned heat exchanger assembly in operation combines four walled members comprising a finned exterior, planner member, two concentric tubular members, and a triangular passageway member. The first concentric tubular walled member having a first inner circumference; and a second concentric tubular walled member having a smaller outer circumference than the inner circumference of the first concentric tubular walled member when assembled together, the first concentric tubular walled member is longitudinally centralized positionally within the first concentric tubular walled member to conduct fluid flow through both tubular members. The first concentric tubular walled member and the second concentric tubular walled members concentrically define the outer circumference and inner circumference of an intermediate inner annular fluid flow channel that contains a helically formed, spirally wound turbulizer strip constructed with a lateral triangular cross-sectional configuration surface and is adapted to be inserted into the inner annular fluid flow channel to form therein the longitudinal triangular flow passageway  
         [0032]     By anchor fastening the helical formed turbulizer strip, member end connection to the second concentric tubular walled member turbulizer strip member is to positionally stabilize, and the fluid conducting through and around the tubular subassembly may be varied to contain fluid flow, and thereby heat exchanger, heat transfer characteristics.  
         [0033]     The four fluid flow conductance paths, including the fluid flow comprising the heat exchanger extends the two concentric tubular fluid, the tubular passageway comprises in combination to provide a versatile heat exchange wherein the heat exchange requirements of a system can be satisfied by the proper pre selected design choice of fluid flow paths and media choice. The surface design of the exterior fins may be corrugated to increase surface area, the tubular member wall there has, internal and external diameters may be varied, the intermediates inner annular fluid flow channel may be varied, and the tubular subassembly may be varied to produce the desired heat exchanger heat transfer results.  
         [0034]     While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects; and we, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of our invention.