Arrangement of Helical Tubes for Efficient Packing and Apparatus Implementing the Same

Abstract

An improved packing efficiency of helical tube bundles in a heat exchanger is achieved by positioning three 3-tube bundles, two twisted in one direction and the third twisted in the opposite direction, and selecting the angular orientation of the tube bundles so as to allow them to nest together in phase so that peaks of adjacent tube bundles are located between each other, forming a bundle overlap. An exemplary application is an EGR cooler.

1 . A heat exchanger for transferring heat between a first fluid and a second fluid comprising:
 a first tube bundle comprising a first set of three tubes adapted to allow the first fluid to flow therethrough, the tubes each having an inlet forming a first set of inlets, the tubes each having an outlet forming a first set of outlets, the first set of inlets being attached to an inlet support at an inlet end, the first set of outlets being attached to an outlet support at an outlet end, each of the first set of tubes following a helical path along a first common helical axis, the helical path of each of the first plurality of tubes having the same twist direction, substantially the same helical pitch and helical radius and symmetric peaks and valleys along the bundle length;   a second tube bundle comprising a second set of three tubes adapted to allow the first fluid to flow therethrough, the second set of tubes each having an inlet forming a second set of inlets, the second set of tubes each having an outlet forming a second set of outlets, the second set of inlets being attached to the inlet support at the inlet end, the second set of outlets being attached to the outlet support at the outlet end, each of the second set of tubes following a helical path along a second common helical axis in the same twist direction as that of the first tube bundle, the helical path of each of the second set of tubes having substantially the same helical pitch and helical radius and symmetric peaks and valleys along the bundle length as the first set of tubes;   a third tube bundle comprising a third set of three tubes adapted to allow the first fluid to flow therethrough, the third set of tubes each having an inlet forming a third set of inlets, the third set of tubes each having an outlet forming a third set of outlets, the third set of inlets being attached to the inlet support at the inlet end, the third set of outlets being attached to the outlet support at the outlet end, each of the third set of tubes following a helical path along a third common helical axis in the opposite twist direction from that of the first and second tube bundles, the helical path of each of the third set of tubes having substantially the same helical pitch and helical radius and symmetric peaks and valleys along the bundle length as the first set of tubes; and   a shell surrounding the first, second and third tube bundles, the shell having an inlet port and an outlet port for flowing the second fluid through the shell past the first, second and third tube bundles and symmetric peaks and valleys along the bundle length;   wherein the helical axes of the first, second and third bundles are parallel to and radially offset from each other and the bundles are positioned for bundle overlap so that peaks of each bundle are in the valleys between the peaks of each adjacent bundle.   
     
     
         2 . The heat exchanger of  claim 1  wherein each bundle has a coil diameter D, a tube diameter d and a bundle center located at the bundle axis and the distance between the centers of adjacent bundles is less than the sum of the diameter length and the tube diameter length. 
     
     
         3 . A heat exchanger for transferring heat between a first fluid and a second fluid comprising:
 a first row of tube bundles, each bundle comprising a set of three tubes adapted to allow the first fluid to flow therethrough, the tubes each having an inlet forming a first set of inlets, the tubes each having an outlet forming a first set of outlets, the first set of inlets being attached to an inlet support at an inlet end, the first set of outlets being attached to an outlet support at an outlet end, each of the tubes following a helical path along a first common helical axis, the helical path of each bundle of tubes having the same twist direction, substantially the same helical pitch and helical radius and symmetric peaks and valleys along the bundle length;   a second row of tube bundles, each bundle comprising a second set of three tubes adapted to allow the first fluid to flow therethrough, the tubes each having an inlet forming a second set of inlets, the tubes each having an outlet forming a second set of outlets, the second set of inlets being attached to the inlet support at the inlet end, the second set of outlets being attached to the outlet support at the outlet end, each of the tubes following a helical path along a second common helical axis in the opposite twist direction from that of the tube bundles in the first row of tube bundles, the helical path of each second row bundle having substantially the same helical pitch and helical radius and symmetric peaks and valleys along the bundle length as the tubes in the first row;   a third row of tube bundles, each bundle comprising a third set of three tubes adapted to allow the first fluid to flow therethrough, the tubes each having an inlet forming a third set of inlets, the tubes each having an outlet forming a third set of outlets, the third set of inlets being attached to the inlet support at the inlet end, the third set of outlets being attached to the outlet support at the outlet end, each of the tubes following a helical path along a third common helical axis in the same twist direction as that of the tube bundles in the first row of tube bundles, the helical path of each third row bundle having substantially the same helical pitch and helical radius and symmetric peaks and valleys along the bundle length as the tubes in the first row; and   a shell surrounding the rows of bundles, the shell having an inlet port and an outlet port for flowing the second fluid through the shell past all of the tube bundles;   wherein the helical axes of the bundles in the first, second and third rows are parallel to and radially offset from each other and the bundles are positioned for bundle overlap so that peaks of each bundle are in the valleys between the peaks of each adjacent bundle.   
     
     
         4 . The heat exchanger of  claim 3  further including a plurality of additional rows of tube bundles wherein rows of tube bundles identical to the first row of tube bundles and rows of tube bundles identical to the second row of tube bundles are positioned so that adjacent rows contain tube bundles of opposite twist, the helical axis of each tube bundle is parallel to the helical axes of the other tube bundles, and each tube bundle is positioned for bundle overlap so that peaks of each bundle are in the valleys between the peaks of adjacent tube bundles.