Heat transfer tube, air-heated evaporator and method for producing a heat transfer tube

Abstract

A heat transfer tube (2), in particular a finned tube, for an air-heated evaporator (1) for heating and/or evaporating cryogenic fluids, having a tube section (8) and a coating (15) which is provided on the outer side of the tube section (8) and has a hydrophilic portion (16) and a hydrophobic portion (17), wherein the hydrophilic portion (16) forms, in the coating (15), seed points (18), which are peripherally enclosed by the hydrophobic portion (16), for condensing air moisture thereon and wherein the seed points (18) have a size of less than 100 nm.

1 . A heat transfer tube ( 2 ), in particular a finned tube, for an air-heated evaporator ( 1 ) for heating and/or evaporating cryogenic fluids, with a tube portion ( 8 ) and a coating ( 15 ), which is provided on the outer side of the tube portion ( 8 ) and has a hydrophilic component ( 16 ) and a hydrophobic component ( 17 ), the hydrophilic component ( 16 ) forming in the coating ( 15 ) seed points ( 18 ), which are peripherally enclosed by the hydrophobic component ( 16 ), for condensing air moisture on the same and the seed points ( 18 ) having a size of less than 100 nm. 
     
     
         2 . The heat transfer tube as claimed in  claim 1 , the seed points ( 18 ) being so small that ice crystals ( 20 ) formed at the seed points ( 18 ) are spherical. 
     
     
         3 . The heat transfer tube as claimed in  claim 2 , the seed points ( 18 ) being so small that the ice crystals ( 20 ) fall off from the heat transfer tube ( 2 ) under their own weight. 
     
     
         4 . The heat transfer tube as claimed in  claim 2 , the diameter (d 18 ) of the seed points ( 18 ) being smaller than a diameter (d 20 ) of the ice crystals ( 20 ) formed at the seed points ( 18 ). 
     
     
         5 . The heat transfer tube as claimed in  claim 1 , the seed points ( 18 ) being punctiform. 
     
     
         6 . The heat transfer tube as claimed in  claim 1 , also having heat transfer ribs ( 11 ), which are provided on the outer side of the tube portion ( 8 ) and on which the coating ( 15 ) is provided. 
     
     
         7 . The heat transfer tube as claimed in  claim 1 , the tube portion ( 8 ) being produced from an aluminum alloy. 
     
     
         8 . The heat transfer tube as claimed in  claim 1 , the coating ( 15 ) being a sol-gel coating. 
     
     
         9 . The heat transfer tube as claimed in  claim 8 , the coating ( 15 ) being a single-component polysiloxane-urethane one-layer coating material. 
     
     
         10 . The heat transfer tube as claimed in  claim 1 , the seed points ( 18 ) being arranged evenly distributed in the hydrophobic component ( 17 ). 
     
     
         11 . The heat transfer tube as claimed in  claim 1 , also having a device ( 21 ) for introducing shocks and/or vibrations into the heat transfer tube ( 2 ). 
     
     
         12 . The heat transfer tube as claimed in  claim 1 , the seed points ( 18 ) being embedded in the hydrophobic component ( 17 ) in such a way that a respective surface ( 19 ) of the seed points ( 18 ) is not covered by the hydrophobic component ( 17 ). 
     
     
         13 . An air-heated evaporator ( 1 ) for heating and/or evaporating cryogenic fluids, with at least one heat transfer tube ( 2 ) as claimed in  claim 1 . 
     
     
         14 . The air-heated evaporator as claimed in  claim 12 , a number of heat transfer tubes ( 2 ) being connected in series. 
     
     
         15 . A method for producing a heat transfer tube ( 2 ), in particular a finned tube, for an air-heated evaporator ( 1 ) for heating and/or evaporating cryogenic fluids, with the following steps:
 providing (S 1 ) a tube portion ( 8 ); and   coating (S 2 ) the outer side of the tube portion ( 8 ) with a coating ( 15 ), which has a hydrophilic component ( 16 ) and a hydrophobic component ( 17 ), the hydrophilic component ( 16 ) forming in the coating ( 15 ) seed points ( 18 ), which are peripherally enclosed by the hydrophobic component ( 17 ), for condensing air moisture on the same, and the seed points ( 18 ) having a size of less than 100 nm.