Heat exchanger for liquid and gaseous media

Abstract

A tube bundle heat exchanger has heat exchanger tubes which are formed over the length of the tube and especially the central region with uniform constricting formations. The degree of constriction, however, is reduced from the central region toward the outlet end, e.g. by reducing the depth of the formations, by increasing the pitch or pitch angle of helical formations, by increasing the spacing of the formations or by any combination thereof. The result is enhanced heat exchange efficiency and/or reduced pressure drop.

We claim:  
     
         1 . A heat exchanger tube for a tube-bundle heat exchanger, said tube having an inlet end, an outlet end and a central portion extending between said ends, said tube being provided with substantially regular formations over said central portion partially projecting into a path of flow of a fluid medium traversing said tube from said inlet end to said outlet end, said formations being configured to reduce a degree of constriction of a flow cross section of said tube toward said outlet end.  
     
     
         2 . The heat exchanger tube defined in  claim 1  wherein a density of said formations per unit length diminishes over an outlet portion of said tube toward said outlet end thereof.  
     
     
         3 . The heat exchanger tube defined in  claim 2  wherein a number of said formations increases over said outlet portion of said tube toward said outlet end.  
     
     
         4 . The heat exchanger tube defined in  claim 2  wherein a spacing of said formations increases over said outlet portion of said tube toward said outlet end.  
     
     
         5 . The heat exchanger tube defined in  claim 2  wherein said formations are in the form of helical grooves and a pitch or pitch angle of said grooves increases over said outlet portion toward said outlet end.  
     
     
         6 . The heat exchanger tube defined in  claim 2  wherein said formations are corrugations in said tube and a spacing of said corrugations increases over said outlet portion toward said outlet end.  
     
     
         7 . The heat exchanger tube defined in  claim 2  wherein said formations are in the form of helical grooves and a depth of said grooves decreases over said outlet portion toward said outlet end.  
     
     
         8 . The heat exchanger tube defined in  claim 2  wherein said formations are corrugations in said tube and a depth of said corrugations decreases over said outlet portion toward said outlet end.  
     
     
         9 . The heat exchanger tube defined in  claim 1  wherein said formations are spaced-apart indentations in a wall of said tube and a spacing of said indentations increases over an outlet portion of said tube toward said outlet end.  
     
     
         10 . The heat exchanger tube defined in  claim 1  wherein said formations are spaced-apart indentations in a wall of said tube and a number of said indentations increases per unit area decreases over an outlet portion of said tube toward said outlet end.  
     
     
         11 . The heat exchanger tube defined in  claim 1  wherein said formations are spaced-apart indentations in a wall of said tube and a depth of said indentations decreases over an outlet portion of said tube toward said outlet end.  
     
     
         12 . The heat exchanger tube defined in  claim 1  wherein said formations are spaced-apart indentations in a wall of said tube and arranged transversely of a flow direction of said fluid medium through said tube.  
     
     
         13 . The heat exchanger tube defined in  claim 1  wherein said formations are spaced-apart indentations in a wall of said tube and arranged in a flow direction of said fluid medium through said tube.  
     
     
         14 . The heat exchanger tube defined in  claim 1  wherein said ends are of circular cross section and said central portion has a flattened cross section.  
     
     
         15 . The heat exchanger tube defined in  claim 1  wherein said tube has a flow cross section wider at said outlet end that at said central portion.  
     
     
         16 . The heat exchanger tube defined in  claim 15  wherein said tube widens continuously toward said outlet end.  
     
     
         17 . The heat exchanger tube defined in  claim 16  wherein said tube has a funnel-shaped outlet portion provided with the reduced reduce degree of constriction of said flow cross section of said tube toward said outlet end.  
     
     
         18 . The heat exchanger tube defined in  claim 1  wherein said central portion has an oval cross section widening into said inlet and outlet ends.  
     
     
         19 . A heat exchanger comprising: 
 a housing;    a tube bundle in said housing having a multiplicity of heat exchanger tubes mounted in tube sheets;    an inlet for a fluid medium communicating with inlet ends of said tubes;    an outlet for said fluid medium communicating with outlet ends of said tubes; and    an inlet and an outlet fitting connected to said housing for passing another medium around said tubes, each of said tubes having a central portion extending between said ends, said tubes each being provided with substantially regular formations over said central portion partially projecting into a path of flow of a medium traversing said tube from said inlet end to said outlet end, said formations being configured to reduce a degree of constriction of a flow cross section of said tube toward said outlet end.    
     
     
         20 . The heat exchanger defined in  claim 19  wherein a density of said formations per unit length diminishes over an outlet portion of each of said tubes toward said outlet end thereof.