Heat exchanger including twisted tubes

Abstract

A heat exchanger comprising a shell having a first end and a second end, a first end plate and a second end plate defining a first volume with the shell that receives a first fluid therein, and at least one heat exchanger tube having a first end affixed to the first end plate and a second end affixed to the second end plate. The at least one heat exchanger tube extends through the second volume and including a cross-section defined by a plurality of lobes extending radially outwardly from the longitudinal center axis thereof. A first fluid passes through the first volume of the shell and a second fluid comprising a hot combustion gas passes through the at least one heat exchanger tube. The cross-section is constant along an entire length of the at least one heat exchanger tube.

What is claimed is: 
     
         1 . A heat exchanger, comprising:
 a shell having a first end and a second end;   a first end plate and a second end plate disposed adjacent the first end of the shell and the second end of the shell, respectively, the shell and the first and second end plates defining a first volume configured to receive a first fluid therein; and   at least one heat exchanger tube having a first end affixed to the first end plate and a second end affixed to the second end plate, the at least one heat exchanger tube extending through the first volume and including a cross-section taken transverse to its longitudinal center axis that is defined by a plurality of lobes, each lobe extending radially outwardly from the longitudinal center axis thereof, the at least one heat exchanger tube including an inner surface and an outer surface defined by a simultaneous rotation and translation of the cross-section along the longitudinal center axis,   wherein the cross-section is constant along an entire length of the at least one heat exchanger tube between the first end plate and the second end plate.   
     
     
         2 . The heat exchange of  claim 1 ;
 wherein a first fluid passes through the first volume of the shell, and   wherein a second fluid comprising a hot combustion gas passes through the at least one heat exchanger tube.   
     
     
         3 . The heat exchanger of  claim 1 , wherein:
 the first end plate defines a first aperture having a same shape as the cross-section of the at least one heat exchanger tube;   the second end plate defines a second aperture having the same shape as the cross-section of the at least one heat exchanger tube, and   the shape of the first aperture and the second aperture conforms to the outer surface of the at least one heat exchanger tube.   
     
     
         4 . The heat exchanger of  claim 3 , wherein the at least one heat exchanger tube further comprises a plurality of heat exchanger tubes, the cross-section of each including four lobes. 
     
     
         5 . The heat exchanger of  claim 4 , wherein each heat exchanger tube includes at least a full twist portion in which each lobe thereof rotates about the longitudinal center axis thereof through 360°. 
     
     
         6 . The heat exchanger of  claim 4 , wherein the first end and the second end of each heat exchanger tube is affixed to the first end plate and the second end plate, respectively, by a weld. 
     
     
         7 . The heat exchanger of  claim 4 , wherein the cross-section of each heat exchanger tube includes four lobes disposed at 90° intervals about the longitudinal center axis. 
     
     
         8 . The heat exchanger of  claim 4 , further comprising a combustion chamber disposed at the first end of the shell, the combustion chamber being in fluid communication with the plurality of heat exchanger tubes. 
     
     
         9 . The heat exchanger of  claim 8 , further comprising a blower in fluid communication with the combustion chamber so that the blower moves the second fluid through the plurality of heat exchanger tubes. 
     
     
         10 . The heat exchanger of  claim 4 , wherein the second volume of the shell includes at least one inlet disposed at its second end and at least one outlet at its first end so that the first fluid flows counter to the second fluid. 
     
     
         11 . The heat exchanger of  claim 4 , wherein the first fluid is water. 
     
     
         12 . The heat exchanger of  claim 4 , wherein a length of each heat exchanger tube is less than 48 inches. 
     
     
         13 . A heat exchanger, comprising:
 a shell having a first end, a second end, and defining a first volume configured to receive a first fluid; and   a first end plate disposed at a first end of the shell, the first end plate defining a first aperture of a first shape;   a second end plate disposed at a second end of the shell, the second end plate defining a second aperture of a second shape;   at least one heat exchanger tube having a first end affixed to the first end plate at the first aperture and a second end affixed to the second end plate at the second aperture, the at least one heat exchanger tube extending through the first volume and including a cross-section taken transverse to its longitudinal center axis that is defined by at least three lobes, each lobe extending radially outwardly from the longitudinal center axis thereof, the at least one heat exchanger tube defining a second volume,   wherein the cross-section is constant along an entire length of the at least one heat exchanger tube between the first end plate and the second end plate, and the first shape and the second shape of the first end plate and the second end plate, respectfully, are the same shape as the cross-section of the at least one heat exchanger tube.   
     
     
         14 . The heat exchanger of  claim 13 , wherein the at least one heat exchanger tube includes an inner surface and an outer surface defined by a simultaneous rotation and translation of the cross-section along the longitudinal center axis. 
     
     
         15 . The heat exchanger of  claim 14 , wherein the first aperture and the second aperture conform to the outer surface of the at least one heat exchanger tube. 
     
     
         16 . The heat exchanger of  claim 15 , wherein the first end and the second end of the at least one heat exchanger tube are affixed to the first and the second end plates, respectively, by welding. 
     
     
         17 . The heat exchanger of  claim 14 , wherein the at least one heat exchanger tube further comprises a plurality of heat exchanger tubes, the cross-section of each including four lobes disposed at 90° intervals about the longitudinal center axis. 
     
     
         18 . The heat exchanger of  claim 17 , further comprising a combustion chamber disposed at the first end of the shell, the combustion chamber being in fluid communication with the second volume of the plurality of heat exchanger tubes. 
     
     
         19 . The heat exchanger of  claim 18 , further comprising a blower in fluid communication with the combustion chamber so that the blower moves the hot combustion gasses through the second volume of the plurality of heat exchanger tubes.