Tube bundle for shell-and-tube heat exchanger and a method of use

Abstract

A tube bundle is provided for a shell-and-tube heat exchanger. The tube bundle includes a plurality of elongated tubes, each of which has an intermediate portion that has a cross section in the form of a flattened circle with at least one axis of symmetry. The tubes are arranged in concentric circles with the axis of symmetry extending tangentially to the circle to facilitate rotational flow of a shell-side fluid.

What is claimed is: 
     
         1 . A tube bundle for a shell-and-tube heat exchanger, said tube bundle comprising:
 a plurality of hollow, elongated tubes extending in parallel and spaced-apart relationship to each other and arranged in a preselected pattern, each of said tubes having a first end for entry of a first fluid for flow within the tube along a longitudinal length of the tube and an opposite second end for the first fluid to exit the tube and an intermediate portion between the first and second ends;   a first tube sheet having holes into which the first ends of the tubes extend and are secured;   a plurality of baffles positioned at spaced apart positions along the longitudinal length of the tubes for supporting the tubes and guiding flow of a second fluid exteriorly of said tubes, each of said baffles having a cutout for passage of fluid and a plurality of openings through which at least some of said tubes are inserted, wherein said cutouts of adjacent ones of said baffles are rotationally offset around a center longitudinal axis of said tube bundle; and   a plurality of flow-diverting plates, each of said plates extending in one direction between and in contact with adjacent ones of said baffles and extending in an opposite direction along said cutouts in said adjacent ones of said baffles.   
     
     
         2 . The tube bundle of  claim 1 , wherein said intermediate portion of each tube has a cross section in the form of a flattened circle with at least one axis of symmetry. 
     
     
         3 . The tube bundle of  claim 2 , wherein said preselected pattern in which said tubes are arranged is a series of concentric circles. 
     
     
         4 . The tube bundle of  claim 3 , wherein the tubes are arranged within each of said concentric circles so that said at least one axis of symmetry of each tube extends tangentially to said concentric circle. 
     
     
         5 . The tube bundle of  claim 4 , wherein said flattened circle is in the form of an elliptical or obround geometric shape. 
     
     
         6 . The tube bundle of  claim 4 , wherein said flattened circle is in the form of an oval or egg-shaped geometric shape. 
     
     
         7 . The tube bundle of  claim 4 , wherein said flattened circle has two axes of symmetry, with one axis being shorter than the other. 
     
     
         8 . The tube bundle of  claim 4 , wherein the cross section of the intermediate portion of each tube has two axes of symmetry, with one axis being shorter than the other, and wherein said first and second ends of the tubes are circular in cross section and one of said first and second ends has a diameter that is less than the length of said shorter axis of symmetry. 
     
     
         9 . The tube bundle of  claim 4 , wherein said intermediate portion of each tube with said cross section in the form of a flattened circle is a majority of the longitudinal length of each tube. 
     
     
         10 . The tube bundle of  claim 4 , wherein said intermediate portion of each tube with said cross section in the form of a flattened circle is at least 75% of the longitudinal length of each tube. 
     
     
         11 . The tube bundle of  claim 4 , wherein said intermediate portion of each tube with said cross section in the form of a flattened circle is at least 90% of the longitudinal length of each tube. 
     
     
         12 . The tube bundle of  claim 4 , wherein said intermediate portion of each tube with said cross section in the form of a flattened circle is at least 95% of the longitudinal length of each tube. 
     
     
         13 . The tube bundle of  claim 4 , wherein said cutout is a sector or segment of the baffle. 
     
     
         14 . A tube bundle for a shell-and-tube heat exchanger, said tube bundle comprising:
 a plurality of hollow, elongated tubes extending in parallel and spaced-apart relationship to each other and arranged in a preselected pattern of a series of concentric circles, each of said tubes having a first end for entry of a first fluid for flow within the tube along a longitudinal length of the tube and an opposite second end for the first fluid to exit the tube and an intermediate portion between the first and second ends, wherein said intermediate portion of each tube has a cross section in the form of a flattened circle with at least one axis of symmetry, wherein the tubes are arranged within each of said concentric circles so that said at least one axis of symmetry of each tube extends tangentially to said concentric circle;   a first tube sheet having holes into which the first ends of the tubes extend and are secured;   a plurality of baffles positioned at spaced apart positions along the longitudinal length of the tubes for supporting the tubes and guiding flow of a second fluid exteriorly of said tubes, wherein each of said baffles is in the form of a partial disc and is positioned in a plane generally perpendicular to a center longitudinal axis of said tube bundle;   a cutout in each of said baffles and intersecting a periphery of said baffle for passage of fluid, wherein said cutouts of adjacent ones of said baffles are rotationally offset around a center longitudinal axis of said tube bundle;   a plurality of openings in each of said baffles through which at least some of said tubes are inserted, wherein said openings are shaped to conform to the cross section of the intermediate portions of the tubes; and   a plurality of flow-diverting plates, each of said plates extending in one direction between and in contact with adjacent ones of said baffles and extending in an opposite direction along said cutouts in said adjacent ones of said baffles.   
     
     
         15 . The tube bundle of  claim 14 , wherein said first tube sheet has additional openings into which the second ends of the tubes extend and are secured. 
     
     
         16 . The tube bundle of  claim 14 , including a second tube sheet having openings into which the second ends of the tubes extend and are secured. 
     
     
         17 . The tube bundle of  claim 14 , wherein each of said tubes has said cross section in the form of a flattened circle along its entire longitudinal length. 
     
     
         18 . A shell-and-tube heat exchanger comprising:
 a shell having an interior volume in which a tube sheet in accordance with  claim 1  is positioned;   an inlet nozzle extending from said shell for introducing a shell-side fluid into the interior volume of the shell;   an outlet nozzle extending from the shell for removing a shell-side fluid from the interior volume of the shell;   another inlet nozzle for introducing a tube-side fluid into the first ends of the tubes within the tube bundle; and   another outlet nozzle for removing the tube-side fluid from the second ends of the tubes within the tube bundle.   
     
     
         19 . A method of operating a shell-and-tube heat exchanger having a shell with an interior volume in which a tube sheet in accordance with  claim 1  is positioned, said method comprising the steps of:
 introducing a shell-side fluid into the interior volume of the shell at one end thereof; 
 causing the shell-side fluid to flow rotationally in the interior volume as it encounters each of the plates before entering each of the cutouts; 
 passing the shell-side fluid through the cutouts in successive ones of the baffles as the shell-side fluid passes from said one end to an opposite end of the shell; 
 introducing a tube-side fluid into first ends of the tubes; 
 flowing the tube-side fluid along the length of the tubes; 
 wherein heat exchange occurs between the tube-side fluid and the shell-side fluid as the tube-side fluid flows along the length of the tubes and the shell-side fluid passes from one end of the shell to the opposite end of shell in said interior volume.