Patent Publication Number: US-2017363358-A1

Title: All-secondary air cooled industrial steam condenser

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to large scale field erected air cooled industrial steam condensers. 
     Description of the Background 
     The current finned tube used in most large scale field erected air cooled industrial steam condensers (“ACC”) uses a flattened tube that is approximately 11 meters long by 200 mm wide (also referred to as “air travel length”) with semi-circular leading and trailing edges, and 18.8 mm internal height (perpendicular to the air travel length). Tube wall thickness is 1.35 mm. Fins are brazed to both flat sides of each tube. The fins are usually 18.5 mm tall, spaced at 11 fins per inch. The fin surface has a wavy pattern to enhance heat transfer and help fin stiffness. The standard spacing between tubes, center to center, is 57.2 mm. The tubes themselves make up approximately one third of the cross sectional face area (perpendicular to the air flow direction); whereas the fins make up nearly two thirds of the cross section face area. There is a small space between adjacent fin tips of 1.5 mm. For summer ambient conditions, maximum steam velocity through the tubes can typically be as high as 28 mps, and more typically 23 to 25 mps. The combined single A-frame design along with these tubes and fins has been optimized based on the length of the tube, the fin spacing, fin height and shape, and the air travel length. The finned tubes are assembled into heat exchanger bundles, typically 39 tubes per heat exchanger bundle, and 10 to 14 bundles are arranged into two heat exchangers arranged together in a single A-frame per fan. The fan is typically below the A-frame forcing air up through the bundles. The overall tube and fin design, and the air pressure drop of the tube and fin combination, has also been optimized to match the air moving capacity of the large (36 ft diameter) fans operating at 200 to 250 hp. This optimized arrangement has remained relatively unchanged across many different manufacturers since the introduction of the single row elliptical tube concept over 20 years ago. 
     The typical A-Frame ACC described above includes both 1 st  stage or “primary” condenser bundles and 2 nd  stage or “secondary” bundles. About 80% to 90% of the heat exchanger bundles are 1 st  stage or primary condenser bundles. The steam enters the top of the primary condenser bundles and the condensate and some steam leaves the bottom. The first stage configuration is thermally efficient; however, it does not provide a means for removing non-condensable gases. To sweep the non-condensable gases through the 1 st  stage bundles, 10% to 20% of the heat exchanger bundles are configured as 2 nd  stage or secondary bundles, typically interspersed among the primary bundles, which draw vapor from the lower condensate manifold. In this arrangement, steam and non-condensable gases travel through the 1 st  stage bundles as they are drawn into the bottom of the secondary bundle. As the mixture of gases travels up through the secondary bundle, the remainder of the steam condenses, concentrating the non-condensable gases. The tops of the secondary bundles are attached to a vacuum manifold which removes the non-condensable gases from the system. 
     Variations to the standard prior art ACC arrangement have been disclosed, for example in US 2015/0204611 and US 2015/0330709. These applications show the same finned tubes, but drastically shortened and then arranged in a series of small A-frames, typically five A-frames per fan. Part of the logic is to reduce the steam pressure drop, which has a small effect on overall capacity at summer condition, but greater effect at a winter condition. Another part of the logic is to weld the top steam manifold duct to each of the bundles at the factory and ship them together, thus saving expensive field welding labor. The net effect of this arrangement, with the steam manifold attached at the factory and shipped with the tube bundles, is a reduction of the tube length to accommodate the manifold in a standard high cube shipping container. Because the tubes are shorter, and therefore the overall amount of surface area is reduced, comparative capacity to the standard single A-frame design of similar overall dimension, summer condition, is reduced by about 3%. 
     SUMMARY OF THE INVENTION 
     The inventions presented herein are 1) a new tube design for use in heat exchanger systems, including but not limited to large scale field erected industrial steam condensers; and 2) a new design for large scale field erected industrial steam condensers for power plants and the like, both of which significantly increase the thermal capacity of the ACC while, in some configurations, reduce the material. Various aspects and/or embodiments of the inventions are set forth below: 
     According to various embodiments of the tube design invention, the tubes are 2.044 m in length, the cross-sectional dimensions of the tubes are 100-200 mm wide, preferably 125 mm wide (air travel length) with a cross-section height (perpendicular to the air travel length) of less than 10 mm, preferably 4-10 mm, more preferably 5.0-9 mm, even more preferably 5.2-7 mm, and most preferably 6.0 mm in height (also “outside tube width”), with fins that are arranged at 9 to 12, preferably 9.8, fins per inch. According to a further preferred embodiment, actual fins may be 17-20 mm in height, preferably 18.5 mm in height and span the space between two adjacent tubes, effectively making 9.25 mm of fin available to each tube on each side. 
     The making of smaller cross-section tubes (same air travel length but significantly smaller height) is directly counter to the current prevailing view in the art that the tubes should be made with as large a cross-section as possible in order to accommodate the massive volumes of steam that is output by a large scale power plant, and because larger tubes drive down costs. While the cost of this arrangement is significantly more than the prior art tube arrangement, the inventors unexpectedly discovered that the increases in efficiency with the lower height tubes (in the most preferred embodiment exceeding 30% greater efficiency as compared to the prior art tubes) more than make up for the increase in cost. This new tube design may be used in large scale field erected industrial steam condensers of the prior art (for example as described in the background section), or it may be used in conjunction with the new ACC design described herein below. 
     Turning to the new design for large scale field erected industrial steam condensers, the primary feature of this invention is that all of the tube bundles of the ACCs according to this invention are constructed as secondary tube bundles, in that steam is fed to upwardly oriented tubes (aligned parallel with the transverse axis of the bundle, each tube generally oriented 25°-35°, and preferably 30° from the vertical) from the bottom and condensate is collected from the tube bundles from the bottom, preferably using a combination/hybrid manifold that both delivers steam to the tubes and collects condensate from the tubes. According to one embodiment, the combination/hybrid manifold may be constructed so that the condensate is prevented from returning down the steam delivery riser(s) and instead is delivered to a condensate recovery tube connected to the combination/hybrid manifold. According to an alternative embodiment, the combination/hybrid manifold may be constructed so that the condensate is allowed to travel down the steam delivery risers and is removed from the steam delivery ducting closer to the ground. The tops of the tubes are connected to a separate manifold for collecting the non-condensable gases. This new “all secondary” ACC arrangement may be configured in an A-Frame, with two secondary bundles joined at the top with a single manifold collecting the non-condensable gases from the tubes, or with two non-condensable manifolds, one at the top of each bundle. 
     As used herein, the terms “all secondary” and “no primaries” shall refer to a large scale field erected air cooled industrial steam condensers in which all of the tube bundles receive steam from the bottom and collect condensate at the bottom, and deliver non-condensable gases out through the top. By comparison, primary tube bundles in a large scale field erected air-cooled industrial steam condenser receive steam at the top, deliver condensate at the bottom, and deliver non-condensable gases at the bottom to a separate, secondary condenser. 
     Preferably, however, the ACC of the invention may be arranged in a V-configuration in which two secondary-only condenser bundles are joined at the bottom with a single combination steam distribution manifold/condensate collection manifold, with a separate non-condensable collection manifold at the top of each bundle. 
     According to the preferred V-configuration embodiment, since the steam manifold is at the bottom of the bundles, entering the manifold at more than one location reduces the size of the manifold and allows the finned tubes to be a bit longer. When combined with smaller cross-sectional tubes described herein (200 mm by less than 10 mm, preferably 4-10 mm, more preferably 5.0-9 mm, even more preferably 5.2-7 mm, and most preferably 6.0 mm in height), the system shows improved performance of at least 25% to 30%, relative to the standard ACC arrangement and configuration described hereinabove, and the unit may be made smaller by a similar amount in plan area. 
     According to a further alternative embodiment, the new ACC design of the present invention may be used with tubes having dimensions of 100 mm by preferably 4-10 mm, more preferably 5.0-9 mm, even more preferably 5.2-7 mm, and most preferably 6.0 mm in height, having offset fins. 
     According to a further embodiment, the new ACC design of the present invention may be used with 120 mm or up to 200 mm by 5 mm to 7 mm tubes having “Arrowhead”-type fins arranged at 9.8 fins per inch. 
     According to yet another embodiment, the new ACC design of the present invention may be used with tubes having “louvered” fins, which perform approximately as well as offset fins, and are more readily available and easier to manufacture. 
     According to preferred and a most preferred embodiments of the invention, combining the most preferred ACC configuration and the most preferred tube dimensions, an ACC of the present invention has the following features and dimensions:
         All secondary bundles (all tubes receive steam from the bottom, distribute condensate through the bottom and distribute non-condensable gases out the top); no primary bundles;   Four, five (most preferred) or six V-shaped bundle pairs per cell/fan;   Tube outside dimension 4-10 mm (preferred 5-7 mm and most preferred: 6.0 mm) by 100-200 mm (most preferred 125 mm) cross section;   Tube spacing c-c 20-29 mm (most preferred: 24.5 mm);   Tube wall thickness 0.7-0.9 mm (most preferred: 0.8 mm);   Tubes per bundle=40-60 (most preferred 50);   Tube length 1,700-2,400 mm (most preferred 2,044 mm);   Arrowhead fins (preferred, not required) spanning between adjacent tubes and thermally connected to both tubes;   Fin height 17-19 (most preferred 18.5 mm (effective height 9.25 mm per tube side);   Air travel length fins 95 mm-195 mm, most preferred: 120 mm.       

     According to this most preferred embodiment, the total bundle face area versus the prior art ACC having the same total fan power, steam volume, and thermal conditions is 79%; likewise, the total plan area for this most preferred embodiment is 79% the area of the prior art ACC having the same total fan power, steam volume, and thermal conditions. 
     Additionally, the ACC design of the present invention can be sited more easily, requiring less overall space within the power plant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view representation of the heat exchange portion of a prior art large scale field erected air cooled industrial steam condenser. 
         FIG. 1B  is a partially exploded close up view of the heat exchange portion of a prior art large scale field erected air cooled industrial steam condenser, showing the orientation of the tubes relative to the steam distribution manifold. 
         FIG. 2  is a perspective view representation of the heat exchange portion of a large scale field erected air cooled industrial steam condenser (“ACC”) according to a first embodiment of the invention. 
         FIG. 3  is a perspective view representation of the heat exchange portion of a large scale field erected air cooled industrial steam condenser (“ACC”) according to a second embodiment of the invention. 
         FIG. 4A  is a perspective view representation of the heat exchange portion of a large scale field erected air cooled industrial steam condenser (“ACC”) according to a third embodiment of the invention. 
         FIG. 4B  is a perspective view representation of the heat exchange portion of a large scale field erected air cooled industrial steam condenser (“ACC”) according to a fourth embodiment of the invention. 
         FIG. 5  is a perspective view of cross-section of a prior art ACC tube and fins. 
         FIG. 6  is a perspective view of a mini-tube and fins according to one embodiment of the invention. 
         FIG. 7  is a perspective view of mini-tubes and fins according to another embodiment of the invention. 
         FIG. 8  is a side view of one street of a large scale field erected air cooled industrial steam condenser according to an embodiment of the invention with V-shaped secondary only heat exchange bundle pairs arrangement shown in  FIG. 4A . 
         FIG. 9  is an end view of the large scale field erected air cooled industrial steam condenser shown in  FIG. 8 . 
         FIG. 10  is a top view the large scale field erected air cooled industrial steam condenser shown in  FIG. 8 , showing one turbine exhaust duct splitting into  6  longitudinal steam headers (6 streets) of 6 cells each. 
         FIG. 11  is a perspective view drawing of a secondary condenser finned tube bundle according to an embodiment of the invention. 
         FIG. 12  is a perspective view photograph of the secondary condenser finned tube bundle rendered in the drawing of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A-Frame ACC with All Secondary Bundles 
     Referring to  FIG. 2 , tubes  2  are arranged in secondary bundles  4 . The longitudinal axes of the tubes  2  are aligned parallel with the transverse axis of the tube bundle, each tube generally oriented 25°-35°, and preferably 30°, from the vertical). Combination steam distribution/condensation collection manifolds  6  are attached at the bottom of each of two secondary bundles  4  that are joined at their top in an A-frame configuration. Steam is distributed to the tubes  2  via the combined steam distribution/condensate collection manifolds  6 , and condensate forms in the tubes  2  as the steam condenses and travels down the tubes  2  into the combined steam distribution/condensate collection manifold  6 . A single non-condensable collection manifold  8  is attached to the top of both bundles  6  to collect the non-condensable gases that travel to the top of the tubes  2 . Steam is supplied to the combined steam distribution/condensate collection manifold  6  from steam duct  10  via risers  12 . Condensed water that collects in the combined steam distribution/condensate collection manifold  6  is carried away from the ACC in condensate recovery tube  14 . 
       FIG. 3  shows an embodiment very similar to the embodiment of  FIG. 2 , except that each bundle  4  is attached at its top to a dedicated non-condensable collection manifold. 
     V-Shaped ACC with All Secondary Bundles 
     Referring to  FIGS. 4A and 4B , tubes  2  are arranged in secondary bundles  4 . The longitudinal axes of the tubes  2  are aligned parallel with the transverse axis of the tube bundle, each tube generally oriented 25°-35°, and preferably 30°, from the vertical). A combination steam distribution/condensation collection manifold  6  is attached at the bottom of two secondary bundles  4  that are joined in a V configuration at an angle of 55°-65, preferably 60°. Steam is distributed to the tubes  2  via the combined steam distribution/condensate collection manifold  6 , and condensate forms in the tubes  2  as the steam condenses and travels down the tubes  2  into the combined steam distribution/condensate collection manifold  6 . A non-condensable collection manifold  8  is attached to the top of both bundles  6  to collect the non-condensable gases that travel to the top of the tubes  2 . Steam is supplied to the combined steam distribution/condensate collection manifold  6  from steam duct  10  via risers  12 . Condensed water that collects in the combined steam distribution/condensate collection manifold  6  is carried away from the ACC in condensate recovery tube  14 . 
     The new ACC design described above may be used with any prior art tubes, including the tubes shown in  FIG. 5  having a length of approximately 11 meters long and a width (or “air travel length”) of 200 mm with semi-circular leading and trailing edges, and having an internal height (perpendicular to the air travel length) 18.8 mm and a tube wall thickness of 1.35 mm, with fins brazed to both flat sides of each tube, usually 18.5 mm tall, spaced at 11 fins per inch. According to a more preferred embodiment, however, the new ACC design of the present invention has the following features and dimensions:
         All secondary bundles (all tubes receive steam from the bottom, distribute condensate through the bottom and distribute non-condensable gases out the top); no primary bundles;   Four, five (most preferred) or six V-shaped bundle pairs per cell/fan;   Tube outside dimension 4-10 mm (preferred 5-7 mm and most preferred: 6.0 mm) by 100-200 mm (most preferred 125 mm) cross section;   Tube spacing c-c 20-29 mm (most preferred: 24.5 mm);   Tube wall thickness 0.7-0.9 mm (most preferred: 0.8 mm);   Tubes per bundle=40-60 (most preferred 50);   Tube length 1,700-2,400 mm (most preferred 2,044 mm);   Arrowhead fins (preferred, not required) spanning between adjacent tubes and thermally connected to both tubes;   Fin height 18.5 mm (effective height 9.25 mm per tube side);   Air travel length fins 95 mm-195 mm, most preferred: 120 mm.       According to this preferred embodiment, an increase in capacity of 25-30% is provided over the prior art A-frame design with standard tubes, for a single cell at constant fan power.   

       FIGS. 8-10  show a representative large scale field erected air cooled industrial steam condenser according to an embodiment of the invention with V-shaped secondary only heat exchange bundle pairs shown in  FIG. 4A . The device shown in  FIGS. 8-10  is a 36 cell (6 streets×6 cell) ACC, with the most preferred embodiment of five bundle pairs per cell, but the invention may be used with any size ACC, and with any number of bundle pairs per cell.