Compact and Efficient Heat Exchanger, Furnace, HVAC Unit, Building, and Method of Making

Abstract

Compact and efficient apparatuses for transferring heat, heat exchangers, and furnaces, as well as HVAC units, HVAC systems, and buildings therewith, plus methods of making such devices. Furnace heat exchangers, for example, have an added stage, added in an unconventional way, that improves efficiency without unduly increasing size, while maintaining required radiuses of bends in tubing. Various embodiments orient bends at particular angles to allow stages to fit together more closely, provide improved structure for connecting stages using two collectors that seal against a common junction plate, provide for indoor air passing through the heat exchanger to pass through different passes of the heat exchanger in an unconventional order in order to provide greater compactness, or a combination thereof, as examples.

1 . An apparatus for transferring heat, the apparatus comprising:
 a first heat-exchanger stage comprising multiple parallel first-stage tubes, each first-stage tube having a first 180 degree bend and a second 180 degree bend; and   a second heat-exchanger stage comprising multiple parallel second-stage tubes, each second-stage tube having a third 180 degree bend;   wherein:
 the first-stage tubes and the second-stage tubes are configured to contain within a flowing first fluid; 
 the first-stage tubes and the second-stage tubes are configured to transfer heat between the first fluid and a second fluid external to the first-stage tubes and external to the second-stage tubes, wherein, when the apparatus is in operation, the second fluid flows in a predominant flow direction past the first-stage tubes and past the second-stage tubes; 
 the first 180 degree bend is oriented at a first angle from the predominant flow direction, wherein an absolute value of the first angle is between 15 degrees and 75 degrees; 
 the second 180 degree bend is oriented at a second angle from the predominant flow direction, wherein an absolute value of the second angle is between 15 degrees and 75 degrees; and 
 the third 180 degree bend is oriented at a third angle from the predominant flow direction, wherein an absolute value of the third angle is less than 15 degrees. 
   
     
     
         2 . The apparatus of  claim 1  wherein the first angle and the second angle have opposite signs. 
     
     
         3 . The apparatus of  claim 1  further comprising a third heat-exchanger stage comprising multiple parallel third-stage tubes. 
     
     
         4 . The apparatus of  claim 3  wherein the first heat-exchanger stage has three passes through the second fluid, the second heat-exchanger stage has two passes through the second fluid, and the third heat-exchanger stage has one pass through the second fluid. 
     
     
         5 . The apparatus of  claim 3  wherein the third heat-exchanger stage comprises multiple fins external to the third-stage tubes; wherein the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage are arranged in an order such that the second fluid passes first through the third heat-exchanger stage and then through at least one pass of the second heat-exchanger stage, and such that the second fluid passes through at least one pass of the first heat-exchanger stage last of the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage; and wherein the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage are arranged and connected in an order such that the first fluid passes first through the first heat-exchanger stage, then through the second heat-exchanger stage, and then through the third heat-exchanger stage. 
     
     
         6 . The apparatus of  claim 3  wherein the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage are arranged in an order such that the second fluid passes first through the third heat-exchanger stage, then through at least one pass of the second heat-exchanger stage, then through at least one pass of the first heat-exchanger stage, then through at least one pass of the second heat-exchanger stage, and then through at least one pass of the first heat-exchanger stage. 
     
     
         7 . The apparatus of  claim 3  wherein the first-stage tubes have a first diameter, the second-stage tubes have a second diameter, the third-stage tubes have a third diameter, the first diameter is substantially larger than the second diameter, and the second diameter is substantially larger than the third diameter. 
     
     
         8 . The apparatus of  claim 3  wherein the first heat-exchanger stage has a first number of tubes, the second heat-exchanger stage has a second number of tubes, the third heat-exchanger stage has a third number of tubes, the first number of tubes is equal to or one less than the second number of tubes, and the third number of tubes is substantially larger than the second number of tubes. 
     
     
         9 . The apparatus of  claim 3  further comprising a junction plate wherein one end of each of the first-stage tubes terminates at the junction plate, two ends of each of the second-stage tubes terminate at the junction plate, and one end of each of the third-stage tubes terminates at the junction plate, wherein the apparatus further comprises a first collector that seals against the junction plate and forms a first enclosed passageway that connects the first-stage tubes to the second-stage tubes, and a second collector that seals against the junction plate and forms a second enclosed passageway that connects the second-stage tubes to the third-stage tubes. 
     
     
         10 . The apparatus of  claim 1  wherein:
 the absolute value of the first angle is between 30 degrees and 60 degrees;   the absolute value of the second angle is between 30 degrees and 60 degrees; and   the absolute value of the third angle is less than 10 degrees.   
     
     
         11 . The apparatus of  claim 1  wherein:
 the absolute value of the first angle is between 40 degrees and 50 degrees;   the absolute value of the second angle is between 40 degrees and 50 degrees; and   the absolute value of the third angle is less than 5 degrees.   
     
     
         12 . The apparatus of  claim 1  wherein:
 the first heat-exchanger stage and the second heat-exchanger stage are arranged and connected in an order such that the first fluid passes first through the first heat-exchanger stage and then through the second heat-exchanger stage; and   the first heat-exchanger stage and the second heat-exchanger stage are arranged in an order such that the second fluid passes first through one pass of the second heat-exchanger stage, then through at least one pass of the first heat-exchanger stage, then through one pass of the second heat-exchanger stage, and then through at least one pass of the first heat-exchanger stage.   
     
     
         13 . The apparatus of  claim 1  wherein the first-stage tubes have a first diameter, the second-stage tubes have a second diameter, and the first diameter is substantially larger than the second diameter; the apparatus further comprising a junction plate, wherein one end of each of the first-stage tubes terminates at the junction plate and at least one end of each of the second-stage tubes terminates at the junction plate, wherein the apparatus further comprises a first collector that seals against the junction plate and forms a first enclosed passageway that connects the first-stage tubes to the second-stage tubes. 
     
     
         14 . The apparatus of  claim 1  further comprising multiple burners wherein each of the first-stage tubes has an entrance end where air enters the first-stage tube, and wherein each burner is located at the entrance end to one of the first-stage tubes and each burner is configured to burn a fuel in one of the first-stage tubes, wherein combustion gasses from the air and the fuel form the first fluid. 
     
     
         15 . The apparatus of  claim 1  wherein the apparatus is a furnace. 
     
     
         16 . The apparatus of  claim 1  wherein the apparatus is an HVAC unit. 
     
     
         17 . The apparatus of  claim 1  wherein the apparatus is an HVAC system. 
     
     
         18 . The apparatus of  claim 1  wherein the apparatus is a building having an HVAC system. 
     
     
         19 . An HVAC unit comprising a furnace for heating indoor air that passes through the HVAC unit, the furnace comprising:
 a first heat-exchanger stage comprising multiple parallel first-stage tubes;   a second heat-exchanger stage comprising multiple parallel second-stage tubes;   a third heat-exchanger stage comprising multiple parallel third-stage tubes;   at least one burner configured to burn a fuel in air forming combustion gasses;   a junction plate wherein an exit end of each of the first-stage tubes terminates at the junction plate, two ends of each of the second-stage tubes terminate at the junction plate, and one end of each of the third-stage tubes terminates at the junction plate;   a first collector that seals against the junction plate forming a first enclosed passageway that transfers the combustion gasses from the first-stage tubes to the second-stage tubes; and   a second collector that seals against the junction plate forming a second enclosed passageway that transfers the combustion gasses from the second-stage tubes to the third-stage tubes; and   wherein the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage are arranged and connected in an order such that the combustion gasses pass first through the first heat-exchanger stage, then through the second heat-exchanger stage, and then through the third heat-exchanger stage.   
     
     
         20 . The HVAC unit of  claim 19  wherein each first-stage tube has a first 180 degree bend and a second 180 degree bend, and each second-stage tube has a third 180 degree bend. 
     
     
         21 . The HVAC unit of  claim 20  wherein, when the HVAC unit is in operation, the indoor air flows in a predominant flow direction past the first-stage tubes, past the second-stage tubes, and past the third-stage tubes;
 the first 180 degree bend is oriented at a first angle from the predominant flow direction, wherein an absolute value of the first angle is between 15 degrees and 75 degrees;   the second 180 degree bend is oriented at a second angle from the predominant flow direction, wherein an absolute value of the second angle is between 15 degrees and 75 degrees; and   the third 180 degree bend is oriented at a third angle from the predominant flow direction, wherein an absolute value of the third angle is less than 15 degrees.   
     
     
         22 . The HVAC unit of  claim 19  wherein the third heat-exchanger stage comprises multiple fins external to the third-stage tubes; wherein the first heat-exchanger stage has three passes through the indoor air, the second heat-exchanger stage has two passes through the indoor air, and the third heat-exchanger stage has one pass through the indoor air; and wherein the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage are arranged in an order such that the indoor air passes first through the third heat-exchanger stage and then through at least one pass of the second heat-exchanger stage, and such that the indoor air passes through at least one pass of the first heat-exchanger stage last of the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage. 
     
     
         23 . The HVAC unit of  claim 19  wherein the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage are arranged in an order such that the indoor air passes first through the third heat-exchanger stage, then through at least one pass of the second heat-exchanger stage, then through at least one pass of the first heat-exchanger stage, then through at least one pass of the second heat-exchanger stage, and then through at least one pass of the first heat-exchanger stage. 
     
     
         24 . The HVAC unit of  claim 19  wherein the first-stage tubes have a first diameter, the second-stage tubes have a second diameter, the third-stage tubes have a-third diameter, the first diameter is substantially larger than the second diameter, and the second diameter is substantially larger than the third diameter; and wherein the first heat-exchanger stage has a first number of tubes, the second heat-exchanger stage has a second number of tubes, the third heat-exchanger stage has a third number of tubes, the first number of tubes is equal to the second number of tubes, and the third number of tubes is substantially larger than the second number of tubes. 
     
     
         25 . A method of making a compact and efficient furnace to heat indoor air by burning a fuel, the method comprising in any order at least the acts of:
 forming or obtaining first-stage tubes, each first-stage tube having a first diameter, a first 180 degree bend and a second 180 degree bend; and   forming or obtaining second-stage tubes, each second-stage tube having a second diameter and a third 180 degree bend;   assembling a first heat-exchanger stage using multiple of the first-stage tubes, wherein the first heat-exchanger stage comprises a first pass, a second pass, and a third pass;   assembling a second heat-exchanger stage using multiple of the second-stage tubes, wherein the second heat-exchanger stage comprises a fourth pass and a fifth pass;   installing a burner at an entrance end of each first-stage tube; and   connecting the second heat-exchanger stage to the first heat-exchanger stage so that, when the furnace is in operation, products of combustion from burning of the fuel at the burner pass first through the first heat-exchanger stage and then through the second heat-exchanger stage, passing first through the first-stage tubes and then through the second-stage tubes;   wherein the acts of forming or obtaining first-stage tubes, forming or obtaining second-stage tubes, assembling the first heat-exchanger stage, and assembling the second heat-exchanger stage comprise forming or obtaining the first-stage tubes and the second-stage tubes, and assembling and arranging the first heat-exchanger stage and the second heat-exchanger stage so that indoor air passing through the furnace, when the furnace is in operation, passes first through the fifth pass, then through the third pass, then through the fourth pass, then through the second pass, and then through the first pass.   
     
     
         26 . The method of  claim 25  wherein the acts of forming or obtaining first-stage tubes, forming or obtaining second-stage tubes, assembling the first heat-exchanger stage and assembling the second heat-exchanger stage comprise forming or obtaining the first-stage tubes and the second-stage tubes, and assembling and arranging the first heat-exchanger stage and the second heat-exchanger stage so that:
 when the furnace is in operation, the indoor air flows in a predominant flow direction past the first-stage tubes and past the second-stage tubes;   the first 180 degree bend is oriented at a first angle from the predominant flow direction, wherein an absolute value of the first angle is between 15 degrees and 75 degrees;   the second 180 degree bend is oriented at a second angle from the predominant flow direction, wherein an absolute value of the second angle is between 15 degrees and 75 degrees; and   the third 180 degree bend is oriented at a third angle from the predominant flow direction, wherein an absolute value of the third angle is less than 15 degrees.   
     
     
         27 . The method of  claim 26  wherein the acts of forming or obtaining first-stage tubes, and assembling the first heat-exchanger stage comprise forming or obtaining the first-stage tubes and assembling and arranging the first heat-exchanger stage so that the first angle and the second angle have opposite signs. 
     
     
         28 . The method of  claim 25  further comprising an act of forming or obtaining a third heat-exchanger stage having multiple third-stage tubes, wherein the third heat-exchanger stage comprises a sixth pass and the third heat-exchanger stage has multiple fins external to the third-stage tubes. 
     
     
         29 . The method of  claim 28  further comprising an act of:
 connecting the third heat-exchanger stage to the second heat-exchanger stage so that, when the furnace is in operation, products of combustion from burning of the fuel at the burner pass first through the first heat-exchanger stage, then through the second heat-exchanger stage, and then through the third heat-exchanger stage, passing first through the first-stage tubes, then through the second-stage tubes, and then through the third-stage tubes;   wherein the acts of forming or obtaining first-stage tubes, forming or obtaining second-stage tubes, forming or obtaining the third heat-exchanger stage, assembling the first heat-exchanger stage, assembling the second heat-exchanger stage, and connecting the third heat-exchanger stage to the second heat-exchanger stage further comprise assembling and arranging the first heat-exchanger stage, the second heat-exchanger stage, and the third heat-exchanger stage so that indoor air passing through the furnace, when the furnace is in operation, passes first through the sixth pass, then through the fifth pass, then through the third pass, then through the fourth pass, then through the second pass, and then through the first pass.   
     
     
         30 . The method of  claim 29  further comprising, in any order, the acts of:
 forming or obtaining a junction plate;   forming or obtaining a first collector; and   forming or obtaining second collector; and   wherein the acts of assembling the first heat-exchanger stage, assembling the second heat-exchanger stage, and connecting the third heat-exchanger stage to the second heat-exchanger stage further comprise, in any order, the acts of:
 terminating one end of each of the first-stage tubes at the junction plate, 
 terminating two ends of each of the second-stage tubes at the junction plate, 
 terminating one end of each of the third-stage tubes at the junction plate, 
 installing the first collector against the junction plate forming a first enclosed passageway that connects the first-stage tubes to the second-stage tubes, and 
 installing the second collector against the junction plate forming a second enclosed passageway that connects the second-stage tubes to the third-stage tubes. 
   
     
     
         31 . The method of  claim 28  wherein the acts of forming or obtaining first-stage tubes, forming or obtaining second-stage tubes, and forming or obtaining the third heat-exchanger stage comprise forming or obtaining the first-stage tubes and the second-stage tubes and forming or obtaining the third heat-exchanger stage so that the third-stage tubes have a third diameter, the first diameter is substantially larger than the second diameter, and the second diameter is substantially larger than the third diameter; and wherein the acts of assembling the first heat-exchanger stage, assembling the second heat-exchanger stage, and forming or obtaining the third heat-exchanger stage comprise assembling the first heat-exchanger stage, assembling the second heat-exchanger stage, and forming or obtaining the third heat-exchanger stage so that the first heat-exchanger stage has a first number of tubes, the second heat-exchanger stage has a second number of tubes, the third heat-exchanger stage has a third number of tubes, the first number of tubes is equal to or one less than the second number of tubes, and the third number of tubes is substantially larger than the second number of tubes.