Shell and tube heat exchanger, finned tubes for such heat exchanger and corresponding method

Abstract

A shell and tube longitudinal flow heat exchanger comprising a containment casing 101 within which a first fluid can flow substantially parallel to the longitudinal axis of said casing 101 , said containment casing 101 accommodating in its interior a bundle of tubes 2 substantially parallel to one another and parallel to the longitudinal axis of said casing 101 and a plurality of grid-shaped baffles 102 substantially transverse to the longitudinal axis of said casing 101 supporting said tubes 2 , a second fluid flowing in said bundle of tubes 2 . Said tubes 2 are provided on at least a part of their outside surface with a plurality of low fins 21 , which are helically arranged on the outer surface of said tubes 2 with a first angle of advancement α and having a profile interrupted by helical grooves 22 having a second angle of advancement β, with α≠β.

1 . A shell and tube longitudinal flow heat exchanger comprising a containment casing within which a first fluid can flow substantially parallel to the longitudinal axis of said casing, said containment casing accommodating in its interior a bundle of tubes substantially parallel to one another and parallel to the longitudinal axis of said casing and a plurality of grid-shaped baffles substantially transverse to the longitudinal axis of said casing supporting said tubes, said bundle of tubes being adapted to the flow of a second fluid therein, characterized in that said tubes are provided on at least a part of their outside surface with a plurality of low fins, said low fins being helically arranged on the outer surface of said tubes with a first angle of advancement α and having a profile interrupted by helical grooves having a second helical angle of advancement β, with α≠β. 
     
     
         2 . A shell and tube longitudinal flow heat exchanger according to  claim 1 , characterized in that said low fins have a height H between 0.5 and 1.5 mm. 
     
     
         3 . A shell and tube longitudinal flow heat exchanger according to  claim 1 , characterized in that said first advance angle α is 20°≤α≤≤45°. 
     
     
         4 . A shell and tube longitudinal flow heat exchanger according to  claim 1 , characterized in that the relative angle between said first angle of advancement α and said second angle of advancement β is between 30° and 60°. 
     
     
         5 . A shell and tube longitudinal flow heat exchanger according to  claim 1 , characterized in that said tubes are provided on their internal surface of a plurality of low fins. 
     
     
         6 . A shell and tube longitudinal flow heat exchanger according to  claim 1 , characterized in that said tubes are provided with finned portions alternated by smooth portions. 
     
     
         7 . A method for manufacturing a finned tube using a machine comprising a working assembly and at least one support assembly, said first working assembly comprising a first rotating finning tool and a second rotating finning tool mounted in sequence on the same driving axis, said first rotating finning tool being provided with a first helical working profile having a first angle of advancement at and said second rotating finning tool being provided with a second helical working profile having a second angle of advancement α 2 , with α 2 ≠α 1 , the method comprising advancing said tube on a plane defined by said support assembly, forming a first fin on said tube by means of said first rotating finning tool, forming a second fin on said tube by means of said second rotating finning tool, the formation of said second fin being immediately subsequent to the formation of said first fin, the height of said first fin being lower than the height of said second fin. 
     
     
         8 . A method for manufacturing a finned tube according to  claim 7 , characterized in that the relative angle between said first angle of advancement at and said second angle of advancement α 2  is between 30° and 60°, and in that the height h of said first fin is ≤0.5 mm, and the height H of said second fin is ≤2 mm. 
     
     
         9 . A finned tube for heat exchangers, in particular for a shell and tube heat exchanger, obtained by a method for manufacturing the finned tube using a machine comprising a working assembly and at least one support assembly, said first working assembly comprising a first rotating finning tool and a second rotating finning tool mounted in sequence on the same driving axis, said first rotating finning tool being provided with a first helical working profile having a first angle of advancement at and said second rotating finning tool being provided with a second helical working profile having a second angle of advancement α 2 , with α 2 ≠α 1 , the method comprising advancing said tube on a plane defined by said support assembly, forming a first fin on said tube by means of said first rotating finning tool, forming a second fin on said tube by means of said second rotating finning tool, the formation of said second fin being immediately subsequent to the formation of said first fin, the height of said first fin being lower than the height of said second fin. 
     
     
         10 . A finned tube for heat exchangers according to  claim 9 , characterized in that it is provided on at least a part of its outside surface with a plurality of low fins, said low fins being helically arranged on the outer surface of said tube with a first angle of advancement α and having a profile interrupted by helical grooves having a second helical angle of advancement β, with α≠β, said first angle of advancement α being 15°≤α≤60°, the relative angle between said first angle of advancement α and said second angle of advancement β being between 30° and 60°, said low fins having a height H between 0.5 and 1.5 mm.