Heat exchanger for water heater

Abstract

A heat exchanger for a water heater having a burner includes an outer tube extending longitudinally along a centerline from a first end adjacent the burner to a second end. Indentations are formed along the length of the outer tube and extend towards the centerline. An inner member extends through the outer tube and between the indentations such that flue gases from the burner flow in a passage between the inner member and the outer tube from the first end to the second end of the outer tube.

What is claimed is: 
     
         1 . A heat exchanger for a water heater having a burner, comprising:
 an outer tube extending longitudinally along a centerline from a first end adjacent the burner to a second end, indentations being formed along the length of the outer tube and extending towards the centerline; and   an inner member extending through the outer tube and between the indentations such that flue gases from the burner flow in a passage between the inner member and the outer tube from the first end to the second end of the outer tube.   
     
     
         2 . The heat exchanger recited in  claim 1 , wherein the indentations are oval in the longitudinal direction of the outer tube. 
     
     
         3 . The heat exchanger recited in  claim 1 , wherein the indentations are parabolic in the radial direction of the outer tube. 
     
     
         4 . The heat exchanger recited in  claim 1 , wherein the inner member is a tube having a closed end for preventing flue gases from flowing through the inner member. 
     
     
         5 . The heat exchanger recited in  claim 1 , wherein the indentations are arranged in pairs having the same longitudinal position and extending towards one another and towards the inner member. 
     
     
         6 . The heat exchanger recited in  claim 1 , wherein the indentations are asymmetrically arranged along the outer tube. 
     
     
         7 . The heat exchanger recited in  claim 1 , wherein the indentations are spaced form the inner member. 
     
     
         8 . The heat exchanger recited in  claim 1 , wherein the indentations contact the inner member. 
     
     
         9 . The heat exchanger recited in  claim 1 , wherein the inner member and outer tube are concentric. 
     
     
         10 . The heat exchanger recited in  claim 1 , wherein the inner member extends from a first end positioned upstream of all the indentations to a second end aligned with the second end of the outer tube. 
     
     
         11 . A water heater including the heat exchanger recited in  claim 1 . 
     
     
         12 . A heat exchanger for a water heater having a burner, comprising:
 an outer tube extending longitudinally along a centerline from a first end adjacent the burner to a second end, indentations being formed along the length of the outer tube and extending towards the centerline; and   an inner member extending through the outer tube from a first end positioned upstream of all the indentations to a second end aligned with the second end of the outer tube, the inner member extending between the indentations such that flue gases from the burner flow in a passage between the inner member and the outer tube from the first end to the second end of the outer tube, wherein the indentations are arranged in pairs having the same longitudinal position and extending towards one another and towards the inner member.   
     
     
         13 . The heat exchanger recited in  claim 12 , wherein the indentations are oval in the longitudinal direction of the outer tube. 
     
     
         14 . The heat exchanger recited in  claim 12 , wherein the indentations are parabolic in the radial direction of the outer tube. 
     
     
         15 . The heat exchanger recited in  claim 12 , wherein the inner member is a tube having a closed end for preventing flue gases from flowing through the inner member. 
     
     
         16 . The heat exchanger recited in  claim 12 , wherein the indentations are asymmetrically arranged along the outer tube. 
     
     
         17 . The heat exchanger recited in  claim 12 , wherein the indentations are spaced form the inner member. 
     
     
         18 . The heat exchanger recited in  claim 12 , wherein the indentations contact the inner member. 
     
     
         19 . The heat exchanger recited in  claim 12 , wherein the inner member and outer tube are concentric. 
     
     
         20 . A water heater including the heat exchanger recited in  claim 12 .