Fireplace with exhaust heat exchanger

Abstract

A heat exchanger system and method for transferring heat from exhaust air from a fireplace to air to be delivered to a living space is described. Heated exhaust air is passed through a heat exchanger before exhaustion from the structure. The heat exchanger couples the exhaust duct and the intake duct and transfers otherwise unused heat from the waste products to the outside air to increase the overall efficiency of the heated product source.

1 . A fireplace heat exchange system comprising:
 a firebox including a plurality of panels combining to define a combustion chamber having a combustion inlet port in fluid communication with a source of combustion air and an exhaust outlet port;   a combustion element adapted to generate heat and exhaust products in the combustion chamber via combustion of a fuel source with combustion air received through the combustion inlet port;   a plenum defining an air intake end and an air output end, the plenum including a plurality of walls combining to define an air pathway between the air intake and air output ends; and   a first heat exchanger including:
 a housing having an outer surface disposed within the plenum, the housing defining a first end in fluid communication with the exhaust outlet port and a second end; and 
 a plurality of baffle plates within the housing, the plurality of baffle plates defining at least a first internal pathway within the outer housing, the first internal pathway extending through a plurality of 180 degree turns from the first end of the heat exchanger to the second end of the heat exchanger. 
   
   
   
       2 . The system of  claim 1 , further comprising a first air assist device adapted to promote a flow of the exhaust products out of the combustion chamber through the exhaust outlet port, through the first internal pathway of the heat exchanger, and out of the distal end of the heat exchanger. 
   
   
       3 . The system of  claim 1 , wherein the air output end is in fluid communication with a living space, the system further comprising a second air assist device adapted to draw air through the air pathway over the outer surface of the heat exchanger and into the living space. 
   
   
       4 . The system of  claim 1 , wherein the first internal pathway of the heat exchanger defines a counter flow component relative to the air pathway between the air intake and air output ends of the plenum. 
   
   
       5 . The system of  claim 1 , wherein the first internal pathway of the heat exchanger further defines a cross-flow component relative to the air pathway between the air intake and air output ends of the plenum. 
   
   
       6 . The system of  claim 1 , further comprising a second internal pathway within the housing separate from the first internal pathway, the second internal pathway extending through a plurality of 180 degree turns from the proximal end of the heat exchanger to the distal end of the heat exchanger. 
   
   
       7 . The system of  claim 1 , wherein the outer surface of the heat exchanger housing includes a plurality of heat transfer assist structures. 
   
   
       8 . The system of  claim 1 , further comprising a second heat exchanger in fluid communication with the first heat exchanger, the second heat exchanger including:
 a housing having an outer surface disposed within the plenum, the housing defining a first end in fluid in communication with the second end of the first heat exchanger and a second end; and   a plurality of baffle plates, the plurality of baffle plates defining at least a first internal pathway within the housing, the first internal pathway extending through a plurality of 180 degree turns from the first end of the second heat exchanger to the second end of the second heat exchanger.   
   
   
       9 . The system of  claim 8 , wherein the second heat exchanger is fluidly coupled to the first heat exchanger in a generally stacked relationship such that the second heat exchanger is spaced a distance from the first heat exchanger, wherein air flows between the outer surfaces of the second heat exchanger and the first heat exchanger. 
   
   
       10 . A fireplace heat exchange system located within a building structure having a plurality of walls defining at least one living space, the system comprising:
 a plenum defining an air intake end and an air output end, the plenum including a plurality of walls defining an air pathway between the air intake and air output ends;   a firebox located within the plenum, the firebox including a plurality of panels defining a combustion chamber having at least one combustion inlet port in fluid communication with a combustion air source, and an exhaust air outlet port;   a combustion element adapted to generate heat and exhaust products in the combustion chamber via combustion of a fuel source with combustion air received through the combustion inlet port; and   a first heat exchanger mounted to the firebox located within the plenum, the first heat exchanger including:
 a housing having an outer surface disposed within the plenum, the housing defining a first end in fluid communication with the exhaust outlet port and a second end; and 
 a plurality of baffle plates within the housing, the plurality of baffle plates defining at least a first internal pathway within the outer housing, the first internal pathway extending through a plurality of 180 degree turns from the first end of the heat exchanger to the second end of the heat exchanger. 
   
   
   
       11 . The system of  claim 10 , further comprising a first air assist device adapted to promote a flow of the exhaust products out of the combustion chamber through the exhaust outlet port, through the first internal pathway of the heat exchanger, and out of the distal end of the heat exchanger. 
   
   
       12 . The system of  claim 10 , wherein the air output end is in fluid communication with a living space, the system further comprising a second air assist device adapted to draw air through the air pathway over the outer surface of the heat exchanger and into the living space. 
   
   
       13 . The system of  claim 10 , the first heat exchanger further comprising a first portion in fluid communication with a second portion, wherein the first portion is angularly offset from the second portion by at least ninety degrees. 
   
   
       14 . The system of  claim 10 , wherein the housing of the first heat exchanger shares a common panel with the firebox to which the first heat exchanger is mounted, wherein no space exists between an outer surface of the firebox and the outer surface of the heat exchanger housing. 
   
   
       15 . The system of  claim 10 , wherein the first heat exchanger is mounted to the firebox such that it is spaced a distance from an outer surface of the firebox, wherein air is permitted to flow between the outer surface of the first heat exchanger housing and the outer surface of the firebox. 
   
   
       16 . The system of  claim 10 , wherein the outer surface of the heat exchanger housing includes a plurality of heat transfer assist structures. 
   
   
       17 . The system of  claim 10 , further comprising a second heat exchanger in fluid communication with the first heat exchanger, the second heat exchanger including:
 a housing having an outer surface disposed within the plenum, the housing defining a first end in fluid communication with the second end of the first heat exchanger and a second end; and   a plurality of baffle plates, the plurality of baffle plates defining at least a first internal pathway within the housing, the first internal pathway extending through a plurality of 180 degree turns from the first end of the second heat exchanger to the second end of the second heat exchanger.   
   
   
       18 . The system of  claim 17 , wherein the second heat exchanger is fluidly coupled to the first heat exchanger in a generally stacked relationship such that the second heat exchanger is spaced a distance from the first heat exchanger, wherein air flows between the outer surfaces of the second heat exchanger and the first heat exchanger. 
   
   
       19 . A method of transferring heat from a combustion chamber to air to be delivered to a living space, the method comprising:
 passing hot exhaust air from a combustion chamber into a first heat exchanger located within a plenum having a plurality of walls defining an air pathway between an air intake end and an air output end, the heat exchanger including a housing defining an exhaust air inlet and an exhaust air outlet, the housing having an outer surface and a plurality of baffle plates within the housing defining an internal pathway from the exhaust air inlet to the exhaust air outlet, causing the exhaust air to flow along the first internal pathway through a plurality of 180 degree turns from the exhaust air inlet of the heat exchanger to the exhaust air outlet of the heat exchanger; and   passing air through the plenum along the air pathway between the air intake and air output end and over the outer surface of the heat exchanger housing such that heat is transferred from the combustion chamber to the air passing through the plenum and from the relatively hot exhaust air passing through the heat exchanger to the air passing through the plenum.   
   
   
       20 . The method according to  claim 19 , further comprising creating positive pressure within the combustion chamber to assist passing exhaust air from the combustion chamber to the heat exchanger, and along the internal pathway located within the heat exchanger housing. 
   
   
       21 . The method according to  claim 19 , further comprising assisting passage of the air through the plenum from the input end to the output end and into the living space. 
   
   
       22 . The method according to  claim 19 , further comprising passing the relatively hot exhaust air from the first heat exchanger to a second heat exchanger located within the plenum, the second heat exchanger in fluid communication with the exhaust air outlet of the first heat exchanger, the second heat exchanger including a housing defining an exhaust air inlet and an exhaust air outlet, the housing having an outer surface and a plurality of baffle plates within the housing, the plurality of baffle plates defining at least a first internal pathway within the housing, the first internal pathway extending through a plurality of 180 degree turns from the exhaust air inlet of the heat exchanger to the exhaust air outlet of the heat exchanger. 
   
   
       23 . The method according to  claim 19 , wherein transferring heat from the combustion chamber to the air passing through the plenum and from the relatively hot exhaust air passing through the heat exchanger to the air passing through the plenum achieves an overall efficiency greater than about 90%.