Looped system fuel-fired fluid heating/storage device

Abstract

A fuel-fired commercial water heater has a three-pass condensing type heat exchanger disposed within its tank and having a vertical flue connected at its lower end to a central collector plenum horizontally circumscribed by an outer plenum to which an exhaust pipe is coupled. A series of vertical tube structures are disposed above and intercommunicate the central and outer collector plenums. The outlet of a fuel burner is coupled to the upper end of the flue and is operative to sequentially flow combustion gases downwardly through the flue into the central collector plenum, upwardly and then downwardly through the tube structures into the outer collector plenum and then outwardly through the exhaust pipe.

1 . A fuel-fired fluid heating apparatus comprising: 
 a tank for holding a fluid to be heated;    a heat exchanger disposed in said tank and having an interior combustion gas flow path defined by: 
 a first pass section having an inlet portion and an outlet portion spaced apart from said inlet portion of said first pass section in a first direction,  
 a central collector plenum coupled to said outlet portion of said first pass section,  
 a second pass section having an inlet portion coupled to said central collector plenum and an outlet portion spaced apart from said inlet portion of said second pass section in a second direction opposite from said first direction,  
 a third pass section having an inlet portion coupled to said outlet portion of said second pass section and an outlet portion spaced apart from said inlet portion of said third pass section in said first direction,  
 an outer collector plenum circumscribing said collector plenum and being coupled to said outlet portion of said third pass section, and  
 an exhaust section coupled to said outer collector plenum; and  
   a combustion system operative to flow hot combustion gases into said inlet portion of said first pass section and then through the balance of said flow path.    
   
   
       2 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said fuel-fired fluid heating apparatus is a fuel-fired water heater.    
   
   
       3 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said heat exchanger is a condensing type heat exchanger.    
   
   
       4 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said combustion system includes a fuel burner having an outlet coupled to said inlet portion of said first pass section.    
   
   
       5 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said first direction extends generally downwardly, and    said second direction extends generally upwardly.    
   
   
       6 . The fuel-fired fluid heating apparatus of  claim 5  wherein: 
 said outer collector plenum has a vertically sloped bottom side with a lowermost portion, and    said exhaust section has an inlet portion coupled to said lowermost portion.    
   
   
       7 . The fuel-fired fluid heating apparatus of  claim 6  further comprising: 
 a condensate drain line interconnected between a bottom side portion of said central collector plenum and said exhaust section.    
   
   
       8 . The fuel-fired fluid heating apparatus of  claim 5  wherein: 
 said central collector plenum extends downwardly beyond said outer collector plenum.    
   
   
       9 . The fuel-fired fluid heating apparatus of  claim 8  wherein: 
 said central collector plenum has a domed bottom side.    
   
   
       10 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said central collector plenum extends past said outer collector plenum in said first direction.    
   
   
       11 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said second and third pass sections are at least partially defined by a U-tube structure extending parallel to said first pass section and having a first open end coupled to said central collector plenum, and a second open end coupled to said outer collector plenum.    
   
   
       12 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said second and third pass sections are defined by a plurality of U-tube structures circumferentially spaced around and extending parallel to said first pass section, each of said U-tube structures having a first open end coupled to said central collector plenum, and a second open end coupled to said outer collector plenum.    
   
   
       13 . The fuel-fired fluid heating apparatus of  claim 1  wherein: 
 said fuel-fired fluid heating apparatus further comprises a transfer plenum disposed exteriorly of said tank,    said second pass section is defined by at least one straight second pass tube having an inlet end coupled to said central collector plenum and an outlet end coupled to said transfer plenum, and    said third pass section is defined by at least one straight third pass tube having an inlet end coupled to said transfer plenum and an outlet end coupled to said outer collector plenum.    
   
   
       14 . The fuel-fired fluid heating apparatus of  claim 13  wherein: 
 said at least one straight second pass tube is a plurality of straight second pass tubes circumferentially spaced around said first pass section, and    said at least one straight third pass tube is a plurality of straight third pass tubes circumferentially spaced around said plurality of straight second pass tubes.    
   
   
       15 . A fuel-fired water heater comprising: 
 a tank for holding water to be heated;    a condensing type heat exchanger disposed within said tank and having: 
 a vertically extending flue having an upper inlet end and a lower outlet end,  
 a central collector plenum coupled to said lower outlet end of said flue,  
 an outer collector plenum horizontally circumscribing said central collector plenum,  
 a plurality of vertically extending inverted U-tubes horizontally spaced around said flue, each said inverted U-tube having a lower inlet end coupled to said central collector plenum, and a lower outlet end coupled to said outer collector plenum, and  
 an exhaust pipe having an inlet portion coupled to said outer collector plenum; and  
   a fuel burner having an outlet coupled to said upper inlet end of said flue, said fuel burner being operative to flow combustion gases through said flue and then the balance of said condensing type heat exchanger.    
   
   
       16 . The fuel-fired water heater of  claim 15  wherein: 
 said fuel-fired water heater is a commercial water heater.    
   
   
       17 . The fuel-fired water heater of  claim 15  wherein: 
 said inlet portion of said exhaust pipe is coupled to a lower side of said outer collector plenum, and    said fuel-fired water heater further comprises a condensate line disposed within said tank and interconnected between said inlet portion of said exhaust pipe and a bottom side portion of said central collector plenum.    
   
   
       18 . The fuel-fired water heater of  claim 15  wherein: 
 said outer collector plenum has a bottom side that slopes downwardly toward said inlet portion of said exhaust pipe, said bottom side having a lowermost portion to which said inlet portion of said exhaust pipe is coupled.    
   
   
       19 . The fuel-fired water heater of  claim 15  wherein: 
 a portion of said central collector plenum extends downwardly beyond said outer collector plenum.    
   
   
       20 . The fuel-fired water heater of  claim 19  wherein: 
 said portion of said central collector plenum has a downwardly domed configuration.    
   
   
       21 . A fuel-fired water heater comprising: 
 a tank for holding water to be heated;    a transfer plenum disposed exteriorly of said tank at an upper end portion thereof;    a condensing type heat exchanger disposed within said tank and having: 
 a vertically extending flue having an upper inlet end and a lower outlet end,  
 a central collector plenum coupled to said lower outlet end of said flue,  
 an outer collector plenum horizontally circumscribing said central collector plenum,  
 a first plurality of vertical tubes horizontally spaced around said flue and having lower inlet ends coupled to said central collector plenum, and upper outlet ends coupled to said transfer plenum,  
 a second plurality of vertical tubes disposed horizontally outwardly of and horizontally spaced around said first plurality of vertical tubes, said second plurality of vertical tubes having upper inlet ends coupled to said transfer plenum, and lower outlet ends coupled to said outer collector plenum, and  
 an exhaust pipe having an inlet portion coupled to said outer collector plenum; and  
   a fuel burner having an outlet coupled to said upper inlet end of said flue, said fuel burner being operative to flow combustion gases through said flue and then the balance of said condensing type heat exchanger.    
   
   
       22 . The fuel-fired water heater of  claim 21  wherein: 
 said fuel-fired water heater is a commercial water heater.    
   
   
       23 . The fuel-fired water heater of  claim 21  wherein: 
 said inlet portion of said exhaust pipe is coupled to a lower side of said outer collector plenum, and    said fuel-fired water heater further comprises a condensate line disposed within said tank and interconnected between said inlet portion of said exhaust pipe and a bottom side portion of said central collector plenum.    
   
   
       24 . The fuel-fired water heater of  claim 21  wherein: 
 said outer collector plenum has a bottom side that slopes downwardly toward said inlet portion of said exhaust pipe, said bottom side having a lowermost portion to which said inlet portion of said exhaust pipe is coupled.    
   
   
       25 . The fuel-fired water heater of  claim 21  wherein: 
 a portion of said central collector plenum extends downwardly beyond said outer collector plenum.    
   
   
       26 . The fuel-fired water heater of  claim 25  wherein: 
 said portion of said central collector plenum has a downwardly domed configuration.