Mitigation of Shell-Side Liquid Maldistribution in Coil Wound Heat Exchanger Bundles

Abstract

Described herein are coil wound heat exchangers (CWHEs), and methods of cooling and/or liquefying streams of fluid using said CWHEs, in which one or more tube layers of the tube bundle are provided with a non-uniform tube winding angle and tube pitch in order to facilitate the equalization of radial pressure imbalances on the shell side of the CWHE, thereby reducing radial maldistribution of fluid on the shell side and improving the heat transfer efficiency of the CWHE.

1 . A coil wound heat exchanger (CWHE) comprising a tube bundle enclosed within a pressure vessel, the tube bundle comprising a plurality of tubes for conveying one or more streams of fluid in heat exchange with a fluid flowing through the pressure vessel externally to the tubes, said tubes being helically wound about a mandrel extending in an axial direction of the bundle so as to form a plurality of tube layers around said mandrel, each of said tube layers comprising one or more of said helically wound tubes, wherein at least one of the tube layers has a first tube winding angle and a first tube pitch at a first axial location of the layer towards one axial end of the bundle, a second tube winding angle and a second tube pitch at a second axial location of the layer towards the opposite axial end of the bundle, and a third tube winding angle and third tube pitch at a third axial location of the layer between the first axial location and second axial location, the third tube winding angle being greater than the first tube winding angle and greater than the second tube winding angle and the third tube pitch being greater than the first tube pitch and greater than the second tube pitch. 
     
     
         2 . A CWHE as claimed in  claim 1 , wherein all or substantially all of the tube layers have a first tube winding angle and a first tube pitch at a first axial location of the layer towards one axial end of the bundle, a second tube winding angle and a second tube pitch at a second axial location of the layer towards the opposite axial end of the bundle, and a third tube winding angle and third tube pitch at a third axial location of the layer between the first axial location and second axial location, for each of said layers the third tube winding angle being greater than the first tube winding angle and greater than the second tube winding angle and the third tube pitch being greater than the first tube pitch and greater than the second tube pitch. 
     
     
         3 . A CWHE as claimed in  claim 2 , wherein the third axial locations of each of said tube layers are at the same or substantially the same axial position of the bundle. 
     
     
         4 . A CWHE as claimed in  claim 1 , wherein in at least one of or all or substantially all of the tube layers the third tube winding angle at the third axial location is equal to or larger than any tube winding angle at any other axial location of the layer between the first axial location and the second axial location of the layer, and the third tube pitch at the third axial location is equal to or greater than any tube pitch at any other axial location of the layer between the first axial location and the second axial location of the layer. 
     
     
         5 . A CWHE as claimed in  claim 1 , wherein in at least one of or all or substantially all of the tube layers the third axial location of the layer is at a point that falls between 10% and 90% of the distance in the axial direction of the bundle between the first axial location and second axial location. 
     
     
         6 . A CWHE as claimed in  claim 1 , wherein in at least one of or all or substantially all of the tube layers the third tube winding angle is at least 5% greater than the first tube winding angle and at least 5% greater than the second tube winding angle. 
     
     
         7 . A CWHE as claimed in  claim 1 , wherein in at least one of or all or substantially all of the tube layers the third tube winding angle is at least 0.5 degrees greater than the first tube winding angle and is at least 0.5 degrees greater than the second tube winding angle. 
     
     
         8 . A CWHE as claimed in  claim 1 , wherein in at least one of or all or substantially all of the tube layers the third tube pitch is at least 5% greater than the first tube pitch and is at least 5% greater than the second tube pitch. 
     
     
         9 . A CWHE as claimed in  claim 1 , wherein in at least one of or all or substantially all of the tube layers the third tube pitch is at least 10% greater than the first tube pitch and is at least 10% greater than the second tube pitch. 
     
     
         10 . A CWHE as claimed in  claim 1 , wherein the CWHE is a vertically oriented CWHE with the axial direction of the bundle being vertical or substantially vertical, the CWHE further comprising a refrigerant dispenser located above the tube bundle for dispensing a refrigerant into the pressure vessel externally to the tubes so that the refrigerant flows downwards through the pressure vessel over and through the tube bundle externally to the tubes. 
     
     
         11 . A CWHE as claimed in  claim 10 , wherein the CWHE has an inlet configured to introduce the one or more streams of fluid into the plurality of tubes of the tube bundle at the bottom of the tube bundle and an outlet configured to withdraw the one or more streams of fluid from the tubes at the top of the tube bundle such that the one or more streams flow upwards through the tubes of the tube bundle. 
     
     
         12 . A CWHE as claimed in  claim 10 , wherein the CWHE is configured to use a liquid or two-phase refrigerant that vaporizes as it flows downwards through the pressure vessel over and through the tube bundle externally to the tubes. 
     
     
         13 . A method of cooling and/or liquefying one or more streams of fluid via heat exchange with a refrigerant using a CWHE as claimed in  claim 1 , wherein the method comprises passing the one or more streams of fluid through the plurality of tubes of the tube bundle and passing the refrigerant through the pressure vessel externally to the tubes. 
     
     
         14 . The method of  claim 13 , wherein the one or more streams of fluid that are to be cooled and/or liquefied comprise a natural gas stream. 
     
     
         15 . The method of  claim 13 , wherein the refrigerant comprises a mixed refrigerant.