Gas Furnace with Heat Exchanger

Abstract

A furnace assembly for use with a gas fuel that includes a cabinet and a burner located in the cabinet that is operable to ignite the gas fuel. The furnace also includes a heat exchanger assembly in communication with the burner and open to receiving the ignited gas fuel, the heat exchanger assembly including tubes. Each tube includes a first section with an inlet, a horizontal section having a first internal diameter, and a vertical section. Each tube also includes a second section extending from the first section and having a second internal diameter less than the first internal dimeter. The second section also includes a serpentine flow path up and down in the vertical direction and an outlet. The gas fuel entering a tube stays in the tube until flowing out of the tube. The furnace also includes a blower operable to move air through the cabinet and over the heat exchanger assembly.

What is claimed is: 
     
         1 . A furnace heat exchanger assembly for combustion of gas fuel heat exchange comprising tubes, wherein each tube comprises:
 a first section comprising an inlet, a horizontal section comprising a first internal diameter, and a vertical section, wherein the horizontal section and the vertical section define an x-y plane; and   a second section extending from the first section and comprising:
 a second internal diameter less than the first internal diameter; 
 a serpentine flow path extending back and forth at least partially in the z-direction; and 
 an outlet; 
   wherein gas fuel entering a tube stays in the tube until flowing out of the tube.   
     
     
         2 . The furnace heat exchanger assembly of  claim 1 , wherein the serpentine flow path also comprises a wave or zig-zag pattern back and forth at least partially in the z-direction. 
     
     
         3 . The furnace heat exchanger assembly of  claim 2 , wherein the tubes are close enough together such that the wave or zig-zag patterns of the second sections are nested. 
     
     
         4 . The furnace heat exchanger assembly of  claim 1 , wherein the first section extends from a panel and the second section terminates in a collector box on a same side as the panel. 
     
     
         5 . The furnace heat exchanger assembly of  claim 1 , wherein the first and the second section of each tube comprise separate parts joined together. 
     
     
         6 . The furnace heat exchanger assembly of  claim 1 , wherein the first section comprises a tapered end positioned within an open end of the second section. 
     
     
         7 . The furnace heat exchanger assembly of  claim 1 , wherein the first section comprises a  90 -degree bend between the horizontal section and the vertical section. 
     
     
         8 . The furnace heat exchanger assembly of  claim 1 , wherein the furnace heat exchanger assembly comprises an annual fuel efficiency rating (AFUE) of 80% and a height low enough to fit in a 30-inch-tall furnace cabinet. 
     
     
         9 . The furnace heat exchanger assembly of  claim 1 , wherein the serpentine flow path comprises at least two changes of direction. 
     
     
         10 . A furnace assembly for use with a gas fuel, comprising:
 a cabinet;   a burner located in the cabinet, wherein the burner is operable to ignite the gas fuel;   a heat exchanger assembly in communication with the burner and open to receiving ignited gas fuel, the heat exchanger assembly comprising tubes, wherein each tube comprises:
 a first section comprising an inlet, a horizontal section comprising a first internal diameter, and a vertical section, wherein the horizontal section and the vertical section define an x-y plane; and 
 a second section extending from the first section and comprising:
 a second internal diameter less than the first internal diameter; 
 a serpentine flow path extending back and forth at least partially in the z-direction; and 
 an outlet; 
 
 wherein the gas fuel entering a tube stays in the tube until flowing out of the tube; and 
   a blower operable to move air through the cabinet and over the heat exchanger assembly.   
     
     
         11 . The furnace assembly of  claim 10 , wherein the serpentine flow path comprises a wave or zig-zag pattern back and forth at least partially in the z-direction. 
     
     
         12 . The furnace assembly of  claim 11 , wherein the tubes of the heat exchanger assembly are close enough together such that the wave or zig-zag patterns of the second sections are nested. 
     
     
         13 . The furnace assembly of  claim 10 , wherein the first section of the tubes of the heat exchanger assembly extends from a panel and the second section terminates in a collector box on a same side as the panel. 
     
     
         14 . The furnace assembly of  claim 10 , wherein the first and the second sections of each tube comprise separate parts joined together. 
     
     
         15 . The furnace assembly of  claim 10 , wherein the first section comprises a tapered end positioned within an open end of the second section. 
     
     
         16 . The furnace assembly of  claim 10 , wherein the first section of the tubes comprises a 90-degree bend between the horizontal section and the vertical section. 
     
     
         17 . The furnace assembly of  claim 10 , wherein the heat exchanger assembly comprises an annual fuel efficiency rating (AFUE) of 80% and a height low enough to fit in a 30-inch-tall furnace cabinet. 
     
     
         18 . The furnace assembly of  claim 9 , further comprising a controller enclosed in the cabinet and operable to continuously monitor and control an operation of the furnace assembly. 
     
     
         19 . The furnace assembly of  claim 9 , further comprising an induced draft blower operable to assist in a removal of an exhaust from the tubes. 
     
     
         20 . The furnace assembly of  claim 9 , wherein the serpentine flow path comprises at least two changes of direction.