An enhanced heat transfer tube with discrete bidirectionally inclined ribs

Abstract

An enhanced heat transfer tube with discrete bidirectionally inclined ribs (DBIR-tube) provides enhanced convective heat transfer both in laminar and turbulent flow regions. The inner surface of the tube is formed with bidirectionally inclined ribs, including left hand inclined ribs and right hand inclined ribs, with the ribs being in the form of discrete strip-like protrusions which respectively form a certain angle with respect to the axis of the tube and incline in two directions. With the hydrodynamic inner diameter of the tube represented by “d”, each bidirectionally inclined rib has a height less than or equal to 0.2 d, a circumferential width less than or equal to 0.5 d, and an axial length less than or equal to 2 d. A certain angle formed between the axis of each rib and the axis of the tube is ±5° to ±85°, the positive sign meaning that the internal rib is orientated in a right hand declining direction, and the negative sign meaning that the internal rib is orientated in a left hand declining direction.

1 . An enhanced heat transfer tube with discrete bidirectionally inclined ribs, wherein the inner surface of the tube is formed with bidirectionally inclined ribs including left hand inclined ribs and right hand inclined ribs, with the ribs being in the form of discrete strip-like protrusions which respectively form a certain angle with respect to the axis of the tube and incline in two directions, and wherein, if the hydrodynamic inner diameter of the tube is represented by “d”, each bidirectionally inclined rib has a height less than or equal to 0.2 d, a circumferential width less than or equal to 0.5 d, and an axial length less than or equal to 2 d.  
   
   
       2 . The enhanced heat transfer tube with discrete bidirectionally inclined ribs of  claim 1 , wherein a certain angle formed between the axis of each rib and the axis of the tube is 5° to ±85°, wherein the positive sign means that the internal rib is orientated in a right hand declining direction, and the negative sign means that the internal rib is orientated in a left hand declining direction.  
   
   
       3 . The enhanced heat transfer tube with discrete bidirectionally inclined ribs of  claim 1 , wherein the shape of the cross section of the rib is in the form of one or combined more of circular arch, rectangle, triangle, circular sector, streamline, and any combination of curve line and straight line.  
   
   
       4 . The enhanced heat transfer tube with discrete bidirectionally inclined ribs of  claim 1 , wherein the axis of the rib is in the form of one or combined more of straight line, zigzag line, arch line, spiral line, and curve line.  
   
   
       5 . The enhanced heat transfer tube with discrete bidirectionally inclined ribs of  claim 1 , wherein the inner surface of the tube is in the form of one or combined more of smooth surface, spiral rib surface, and low rib surface.  
   
   
       6 . The enhanced heat transfer tube with discrete bidirectionally inclined ribs of  claim 1 , wherein the outer surface of the tube is in the form of one or combined more of grooved surface, smooth surface, spiral rib surface, low rib surface, and finned surface.