Heater Exchanger for Water Heaters

Abstract

An improved heat exchanger for a water heater is provided. The heat exchanger includes a plurality of dimples are indented into the surface of the flue tubes used in the heat exchanger. The arrangement, size, and shape of the dimples are optimized such that the thermal efficiency of the heat exchanger is maximized while still maintaining the structural integrity of the flue tubes. Additionally, the heat exchanger includes diverters that directly connect the second and third-pass flue tubes such that the flow of hot gas from the combustions system through the flue tubes occurs entirely under the top pan of the water heater.

That which is claimed is: 
     
         1 . A water heater comprising:
 a combustion system;   a water tank;   a top cover assembly having a top surface; and   a multi-pass heat exchanger positioned in the water tank and underneath the top cover assembly, wherein the multi-pass heat exchanger comprises flue tubes arranged such that hot gas received from the combustion system flows through the multi-pass heat exchanger without flowing onto or above the top cover assembly, and wherein the flue tubes include a plurality of dimples positioned along a length of the flue tubes.   
     
     
         2 . The water heater of  claim 1 , wherein the flue tubes are a carbon steel material. 
     
     
         3 . The water heater of  claim 1 , wherein the plurality of dimples include a first dimple positioned across from a second simple, and a third dimple and a fourth dimple staggered from the first dimple and second dimple. 
     
     
         4 . The water heater of  claim 3 , wherein a spacing between the first dimple and the third dimple is within a range of 2.5 inches to 3 inches and a depth of the plurality of dimples is within a range of 0.75 inches to 1 inch. 
     
     
         5 . The water heater of  claim 1 ,
 wherein the flue tubes include a first-pass flue tube, a first second-pass flue tube, and a first third-pass flue tube,   wherein the first-pass flue tube is configured to pass hot gas from the combustion system to the first second-pass flue tube, and   wherein the first second-pass flue tube is configured to pass the hot gas to the first third-pass flue tube.   
     
     
         6 . The water heater of  claim 5 ,
 wherein the first-pass flue tube is centrally disposed within the water tank,   wherein the first second-pass flue tube is radially disposed from the first-pass flue tube, and   wherein the first third-pass flue tube is radially disposed from the first-pass flue tube.   
     
     
         7 . The water heater of  claim 5 , further comprising:
 a second third-pass flue tube connected to the first second-pass flue tube.   
     
     
         8 . The water heater of  claim 7 , further comprising:
 a second second-pass flue tube and a third second-pass flue tube;   a third third-pass flue tube and a fourth third-pass flue tube connected to the second second-pass flue tube; and   a fifth third-pass flue tube and a sixth third-pass flue tube connected to the third second-pass flue tube.   
     
     
         9 . The water heater of  claim 8 , wherein the third third-pass flue tube and the fourth third-pass flue tube are connected to the second second-pass flue tube underneath the top cover assembly, and the fifth third-pass flue tube and the sixth third-pass flue tube are also connected to the third second-pass flue tube underneath the top cover assembly. 
     
     
         10 . The water heater of  claim 8 , further comprising:
 a fourth second-pass flue tube; and   a seventh third-pass flue tube and an eighth third-pass flue tube connected to the fourth second-pass flue tube.   
     
     
         11 . A heat exchanger comprising:
 a first-pass flue tube configured to receive hot gas from a combustion system of a water heater;   a first second-pass flue tube connected to the first-pass flue tube and configured to receive the hot gas from the first-pass flue tube; and   a first third-pass flue tube connected to the first second-pass flue tube and configured to receive the hot gas from the first second-pass flue tube,   wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube are positioned in a water tank of the water heater and underneath a top cover assembly of the water heater, and   wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube include a plurality of dimples.   
     
     
         12 . The heat exchanger of  claim 11 , wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube are a carbon steel material. 
     
     
         13 . The heat exchanger of  claim 11 , wherein the plurality of dimples include a first dimple positioned across from a second simple, and a third dimple and a fourth dimple staggered from the first dimple and second dimple. 
     
     
         14 . The heat exchanger of  claim 13 , wherein a spacing between the first dimple and the third dimple is within a range of 2.5 inches to 3 inches and a depth of the plurality of dimples is within a range of 0.75 inches to 1 inch. 
     
     
         15 . The heat exchanger of  claim 11 ,
 wherein the first-pass flue tube is centrally disposed within the water tank,   wherein the first second-pass flue tube is radially disposed from the first-pass flue tube, and   wherein the first third-pass flue tube is radially disposed from the first-pass flue tube and is adjacent to the first second-pass flue tube.   
     
     
         16 . The heat exchanger of  claim 11 , further comprising:
 a second third-pass flue tube also connected to the first second-pass flue tube.   
     
     
         17 . The heat exchanger of  claim 16 , further comprising:
 a second second-pass flue tube and a third second-pass flue tube;   a third third-pass flue tube and a fourth third-pass flue tube connected to the second second-pass flue tube; and   a fifth third-pass flue tube and a sixth third-pass flue tube connected to the third second-pass flue tube.   
     
     
         18 . The heat exchanger of  claim 17 , wherein the third third-pass flue tube and the fourth third-pass flue tube are connected to the second second-pass flue tube underneath the top cover assembly, and the fifth third-pass flue tube and the sixth third-pass flue tube are also connected to the third second-pass flue tube underneath the top cover assembly. 
     
     
         19 . The heat exchanger of  claim 17 , further comprising:
 a fourth second-pass flue tube; and   a seventh third-pass flue tube and an eighth third-pass flue tube connected to the fourth second-pass flue tube.   
     
     
         20 . A heating appliance comprising:
 a combustion system;   a water tank;   a top cover assembly having a top surface, wherein the combustion system is disposed on the top surface; and   a multi-pass heat exchanger comprising:
 a first-pass flue tube configured to receive hot gas from a combustion system; 
 a first second-pass flue tube connected to the first-pass flue tube and configured to receive the hot gas from the first-pass flue tube; and 
 a first third-pass flue tube connected to the first second-pass flue tube and configured to receive the hot gas from the first second-pass flue tube, 
 wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube are positioned in a water tank of the heating appliance and underneath the top cover assembly of the heating appliance, and 
 wherein the first-pass flue tube, first second-pass flue tube, and first third-pass flue tube include a plurality of dimples.