Abstract:
The invention is a heat exchanger that transfers heat from one medium to another by pulling a heated medium through a series of expansion chambers and water-immersed tubes that transfers the heat from one medium to another, including a secondary set of coils to increase the efficiency.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    None. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
       [0002]    None. 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    None. 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0004]    None. 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    The invention pertains to fuel-fired heat exchanger using a combustion chamber and heat transfer radiators. 
         [0007]    2. Background Art 
         [0008]    Traditional direct-vent heat exchangers comprise a water tank, a combustion chamber where a gas fuel burns to heat air, and a flue system in which air circulates in a radiator surrounding by water, the radiator transferring the heat carried by the air to the water. These systems often have a sealed combustion chamber and blowers to assist air flow through the system. 
         [0009]    Heat exchangers are known in the industry; in particular, water heater construction techniques are well established, with many types of heater combustion chambers. The prior art is rich in very old construction and patented approaches to the many difficulties of designing an effective heat exchangers, many of which include: the transfer of heat which comes from a combustion chamber to the water, condensation problems, heat transfer efficiency, and the challenge of a system that can be kept clean over the life of the system. 
         [0010]    An overview of the prior art includes patented water tanks, e.g., U.S. Pat. No. 7,500,454, heat chambers, e.g., U.S. Pat. No. 7,946,257, unique duct and flue systems e.g., U.S. Pat. No. 7,992,526 and U.S. Pat. No. 7,997,236, fin-equipped metal fins to increase efficiency, e.g., U.S. Pat. No. 7,836,856, and pipe assemblies to conduct the heat from the air to water, e.g., U.S. Pat. No. 7,434,545, U.S. Pat. No. 7,458,340, and U.S. Pat. No. 7,523,721. 
         [0011]    As these and other patents show, inventors and the heat exchanger industry continues to struggle in building a more efficient water heater, continuously looking for higher efficiency, longer productive life, less expensive manufacturing costs, and less frequent cleaning requirements. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    The invention is a heat exchanger that transfers heat from one medium to another, typically heated air to water by pulling the heated air through a series of chambers and water-immersed tubes that transfers the heat from the air to the water, including a secondary set of coils that encircle the outermost portion of the water chamber to increase the efficiency. The size of the tube acts as a metering device that slows the velocity of the medium, which also reduces the pressure in the radiator/flue portion of the exchanger. The slower velocity of the transfer medium, coupled with the lowed pressure allows for the medium to be cooled or heated more effectively. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0013]    FIG.  1 —A side plan view of an embodiment of the invention showing the inside wall  25  and secondary transfer coil  37 , and outer wall  27  shown with invisible lines. 
           [0014]    FIG.  2 —A sectional view of an embodiment of the invention illustrated in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Water is efficiently heated by use of the present invention, a dual-walled heat exchanger  11  including: a main water tank  13  surrounded by an inner wall  25 , a preheat tank  41  defined as the volume between the inner wall  25  and outer wall  27  of the water heater, a heat transfer apparatus sitting inside the main water tank  13 , a gas-fired combustion chamber  15 , a primary gas expansion chamber  17 , a secondary expansion sphere  19 , a system of thermal transfer pipes  21  connecting the primary gas expansion sphere  17  and secondary gas expansion sphere  19 , and an exhaust flue  23  which contains exhaust gases from the secondary expansion sphere  19  to a secondary transfer coil  37  mounted in the preheat tank  41  which preheats water before it enters the main volume of the tank  13  through main tank entrance portal  43 . An optional pump  29  pulls heated air through the system. Heated water leaves the exchanger  11  through water exit portal  45 . 
         [0016]    Water flow—Water flows under pressure into the heat exchanger  11  initially through portal  35  into the preheat tank  41 . The water flows through the preheat tank  41 , slowly warmed by the secondary transfer coil  37 , and from the preheat tank through the main tank entrance portal  43  into the main tank  13 . Once inside the main tank  13 , the water is heated by the chambers  15 ,  17 ,  19 , and thermal transfer pipes  21  before leaving the main tank  13  through the exit portal  45 . 
         [0017]    Air flow—As shown in  FIG. 2 , the typical construction assumes a gas-fired combustion changer  15  in which a gas burner creates heated air which rises or is pulled by a pump into the primary gas expansion chamber  17 . Existing heat exchangers use both sealed and unsealed combustion chambers. Sealed combustion chambers are preferred, but not necessary. The gas expands in the primary chamber  17  and releases heat through the walls of the chamber  17  and into water in the tank  13 . As the hot air moves through the system, it then proceeds swiftly through the smaller thermal transfer pipes  21  into the secondary gas expansion chamber  19 . 
         [0018]    Gas moves slowly through the secondary gas expansion chamber  19  and into the exhaust flue  23 . Once in the flue  23 , the heat transfer continues as the air swiftly travels through a secondary heat transfer coil  37  mounted between the inner wall  25  and the outer wall  27  before leaving the exchanger  11 . The embodiment can transfer so much heat from the heated air to the water in the tank  13  that it creates condensation in the exhaust flue. The resulted condensation created in this way will simply come down through the secondary heat transfer coil  37 , providing desalinated water that can be collected from the gas exit portal  39  as it leaves the water heater. 
         [0019]    Optional components—An optional pump is located outside and separate from this exchanger, and is not a necessary part of the invention, but only a serves to increase speed of exhaust gases and thereby increase the operational speed as a pre-heater to the incoming water which enters through a water entrance port  35  near the base of the water heater  11 . Other optional components include a baffle in the primary expansion chamber  17  and radiation fins  47  on any of the spherical chambers in the water heater  15 ,  17 ,  19 , symbolically shown in  FIG. 2  on the combustion chamber  15 , but not limited solely to that particular chamber. 
         [0020]    Heat transfer pipes  21  shown in  FIG. 2  can be a variable shape and length; the embodiment shown includes a thermal transfer pipe configuration of eight pipes, four of them looped  31 , and four more as simple connection pipes  33 . (Four of the eight pipes are not shown in  FIG. 2  because it is a sectional view.) 
         [0021]    The current invention uses spherical combustion and expansion chambers because they have been found to be most efficient, but need not be in order for the invention to function. The exchanger employs gas expansion in the spherical chambers  15 ,  17 ,  19  and the thermal transfer tubes  21  to heat the water inside the tank  13 . This approach and particular construction of the device as described provides high transfer of energy from the combusted gas fuel to the water flowing through the exchanger  11 . 
         [0022]    While this invention has been described as it is currently built, the invention is not limited to the disclosed embodiments, but can be employed in various equivalent arrangements included within the spirit and scope of the claims.