Heat exchanger tube with enhanced heat transfer co-efficient and related method

Abstract

A method of enhancing the heat transfer coefficient of a tube flowing a fluid in the tube in heat exchange relation with a second fluid external to the tube includes forming a patterned array of grooves on the interior surface of the tube. Each tube has a depth-to-width ratio of 0.10 to 0.30, and the grooves may be formed by mechanical pressing, pulsed ECM or electrodischarge processes.

1 . A method of enhancing the heat transfer coefficient of a tube flowing a fluid in the tube in heat exchange relation with a second fluid external to the tube comprising forming a patterned array of grooves on the interior surface of the tube. 
   
   
       2 . The method of  claim 1  wherein said grooves have a depth of greater than about 0.2% of the internal tube diameter. 
   
   
       3 . The method of  claim 1  wherein said grooves have a depth of between 1% and 5% of the internal tube diameter. 
   
   
       4 . The method of  claim 1  wherein said grooves have a semi-spherical cross section. 
   
   
       5 . The method of  claim 1  wherein said grooves have a depth-to-width ratio of 0.10 to 0.30 
   
   
       6 . The method of  claim 1  wherein said grooves are formed by a mechanical pressing. 
   
   
       7 . The method of  claim 1  wherein said grooves are formed by pulsed ECM or electro-discharge processes. 
   
   
       8 . The method of  claim 1  wherein said grooves are criss-crossed. 
   
   
       9 . The method of  claim 1  comprising forming each grooves with a flat bottom and angled side walls. 
   
   
       10 . The method of  claim 1  comprising forming at least some of the grooves to run generally parallel to each other but with varying spacing therebetween. 
   
   
       11 . The method of  claim 1  comprising forming the tube to vary density of the grooves along the length of the tube. 
   
   
       12 . A heat exchanger tube comprising a hollow tube having an interior surface covered substantially by an array of grooves, said grooves having a depth-to-width diameter ratio of 0.10 to 0.30. 
   
   
       13 . The heat exchanger tube of  claim 12  wherein said grooves have a depth of greater than about 0.2% of the internal tube diameter. 
   
   
       14 . The heat exchanger tube of  claim 13  wherein said grooves have a depth of between 1% and 5% of the internal tube diameter. 
   
   
       15 . The heat exchanger tube of  claim 12  wherein said grooves have a semi-spherical cross section. 
   
   
       16 . The heat exchanger tube of  claim 12  wherein said grooves are criss-crossed. 
   
   
       17 . A heat exchanger comprising a plurality of interconnected tubes adapted to carry a first fluid in heat exchange relationship with a second fluid flowing across said plurality of interconnected tubes, each tube having an interior surface covered substantially by an array of intersecting grooves in a criss-crossed pattern, said grooves having a depth-to-tube diameter ratio of 0.10 to 0.30. 
   
   
       18 . The heat exchanger of  claim 17  wherein said grooves have a depth of greater than about 0.2% of the internal tube diameter. 
   
   
       19 . The heat exchanger of  claim 18  wherein said grooves have a depth of between 1% and 5% of the internal tube diameter. 
   
   
       20 . The heat exchanger of  claim 17  wherein said grooves have a semi-spherical cross section.