High performance micro-rib tube

Abstract

A heat transfer tube utilized in a condenser or an evaporator of a heat exchanger includes a plurality cavities to increase heat transfer. A plurality of substantially trapezoidal shaped substantially parallel ribs are formed by a first roll embossing step. A second roll embossing step is repeated at a different helix angle to slightly deform the ribs, creating a plurality of substantially parallel microgrooves and a cavity on the interior end of each microgroove. The cavities are substantially branched or substantially V-shaped and increase heat transfer.

What is claimed is:  
     
         1 . A heat transfer tube comprising: 
 a tubular member having an interior surface, an interior diameter D, and a longitudinal axis;    a plurality of substantially parallel ribs formed on said interior surface having a height h 2 ; and    a plurality of cavities formed on said interior surface extending at an angle from said plurality of substantially parallel ribs, each of said plurality of cavities having a cavity depth less than 0.75 h 2 .    
     
     
         2 . The heat transfer tube as recited in  claim 1  wherein said plurality of substantially parallel ribs are substantially trapezoidal.  
     
     
         3 . The heat transfer tube as recited in  claim 1  wherein each of said plurality of cavities are substantially V-shaped.  
     
     
         4 . The heat transfer tube as recited in  claim 1  wherein each of said plurality of cavities has a cavity opening less than 0.005 of an inch.  
     
     
         5 . The heat transfer tube as recited in  claim 1  wherein each of said plurality of cavities has a cavity depth less than 0.4 h 2 .  
     
     
         6 . The heat transfer tube as recited in  claim 1  wherein the ratio of said height h 2  of each of said ribs to said interior diameter D of said tubular member ranges from 0.01 to 0.05.  
     
     
         7 . The heat transfer tube as recited in  claim 1  wherein the ratio of said height h 2  of each of said ribs to said interior diameter D of said tubular member ranges from 0.015 to 0.03.  
     
     
         8 . The heat transfer tube as recited in  claim 1  wherein said plurality of cavities formed in said interior surface extend at an angle from said longitudinal axis of said tubular member ranging from 0 to 45 degrees.  
     
     
         9 . The heat transfer tube as recited in  claim 1  wherein said tubular member further includes a circumference and a number of said plurality of deformed ribs per unit length of said circumference ranges between 20 and 100.  
     
     
         10 . The heat transfer tube as recited in  claim 1  wherein each of said plurality of ribs has a base width ranging from 0.005 to 0.01 inch and an apex angle ranging from 0 to 60 degrees.  
     
     
         11 . A heat exchanger comprising at least one heat transfer tube having an interior surface, a plurality of substantially parallel ribs formed on said interior surface having a height h 2 , and a plurality of cavities formed on said interior surface extending at an angle from said plurality of substantially parallel ribs, each of said plurality of cavities having a cavity depth less than 0.75 h 2 .  
     
     
         12 . The heat exchanger as recited in  claim 11  wherein said heat exchanger is an evaporator.  
     
     
         13 . The heat exchanger as recited in  claim 11  wherein said heat exchanger is a condenser.  
     
     
         14 . A method for making a heat transfer tube comprising: 
 roll embossing a metal strip to form a plurality of substantially parallel ribs formed on said interior surface having a height h 2 ;    re-roll embossing said metal strip to deform said plurality of ribs in said interior surface to form a plurality of cavities extending at an angle from a longitudinal axis of said tubular member plurality of cavities having a cavity depth less than 0.75 h 2 .    forming said metal strip into a tubular member having an interior surface, an interior diameter D, and said longitudinal axis.    
     
     
         15 . The method as recited in  claim 14  wherein the step of roll embossing said metal strip includes forming a plurality of substantially parallel ribs having a substantially trapezoidal shape.  
     
     
         16 . The method as recited in  claim 14  wherein the step of re-roll embossing said metal strip includes deforming said plurality of ribs to form a plurality of substantially V-shaped cavities.  
     
     
         17 . The method as recited in  claim 14  wherein the step of re-roll embossing said metal strip is rolled at an angle from said longitudinal axis of said tubular member ranging from 0 to 45 degrees.  
     
     
         18 . The method as recited in  claim 14  wherein the step of re-roll embossing said metal strip includes forming between 20 and 100 of said plurality of deformed ribs per a unit length of a circumference of said heat transfer tube.  
     
     
         19 . The method as recited in  claim 14  wherein the ratio of said height h 2  of each of said ribs to said interior diameter D of said tubular member ranges from 0.01 to 0.05.  
     
     
         20 . The method as recited in  claim 14  wherein each of said plurality of ribs has a base width ranging from 0.005 to 0.01 inch and an apex angle ranging from 0 to 60 degrees.