Heat transfer tube and method of and tool for manufacturing heat transfer tube having protrusions on inner surface

Abstract

An improved heat transfer tube and a method of formation thereof. The inner surface of the tube is enhanced with a plurality of protrusions that reduce tube side resistance and improve overall heat transfer performance. The protrusions create additional paths for fluid flow within the tube and thereby enhance turbulence of heat transfer mediums flowing within the tube. This increases fluid mixing to reduce the boundary layer build-up of the fluid medium close to the inner surface of the tube, such build-up increasing the resistance and thereby impeding heat transfer. The protrusions also provide extra surface area for additional heat exchange. The method of this invention includes using a tool, which can easily be added to existing manufacturing equipment, having a cutting edge to cut through ridges on the inner surface of the tube to create ridge layers and a lifting edge to lift the ridge layers to form the protrusions. In this way, the protrusions are formed without removal of metal from the inner surface of the tube, thereby eliminating debris which can damage the equipment in which the tubes are used. The protrusions on the inner surface of the tube can be formed in the same or a different operation as formation of the ridges.

We claim:  
     
         1 . A tube comprising an inner surface, an outer surface, and a longitudinal axis, wherein the inner surface comprises at least one protrusion cut at a cutting depth from a ridge formed along the inner surface of the tube.  
     
     
         2 . A tool for cutting the inner surface of a tube comprising a tool axis and at least one tip formed by the intersection of at least a first plane, a second plane, and a third plane and having a cutting edge and a lifting edge.  
     
     
         3 . A method of manufacturing a tube having a longitudinal axis comprising: 
 a. cutting through at least one ridge formed along an inner surface of the tube to a cutting depth and at an angle relative to the longitudinal axis to form ridge layers; and    b. lifting the ridge layers to form protrusions having a protrusion height, protrusion thickness, and protrusion pitch.    
     
     
         4 . A method of enhancing the inner surface of a tube, comprising: 
 a. mounting a tool onto a shaft, the tool comprising a tool axis and at least one tip formed by the intersection of at least a first plane, a second plane, and a third plane and having a cutting edge and a lifting edge;    b. positioning the tool in the tube;    c. causing relative rotation and relative axial movement between the tube and the tool to cut at least partially though at least one ridge formed along the surface of the tube to form ridge layers and lift the ridge layers to form protrusions.