Patent Publication Number: US-2017356691-A1

Title: Swimming Pool Heat Exchangers And Associated Systems And Methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority benefit of U.S. Provisional Application No. 62/348,186, filed Jun. 10, 2016, which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to swimming pool heat exchangers and associated systems and methods and, in particular, to heat exchangers including a plurality of titanium tubes with welded copper fins for improved heat transfer in swimming pool heater applications. 
     BACKGROUND 
     Various types of heaters have been used over the years for heating fluids in applications such as residential heating systems and swimming pools. Although discussed herein with respect to water tube heat exchangers, fire tube heat exchangers have also been used in the industry. Most heaters include a heat exchanger disposed proximate a source of heat through which the fluid to be heated passes. The heat exchanger generally includes a metal conduit through which the fluid to be heated can pass and is positioned above a burning gas to absorb the heat of combustion and conduct it to the fluid passing through the conduit. To increase the efficiency of heat transfer, the heat exchanger can be configured to maximize the exterior surface area exposed to the heat of combustion by using metal fins on the conduit. 
     Different materials of construction for heat exchangers have been used. The advantages of using titanium tubing with swimming pool water to avoid corrosion has been well documented, and titanium tubing has been widely used in mechanical heating appliances (e.g., heat pumps). In particular, titanium has been successfully used with mechanical heating appliances due to the heat exchanger being used for a liquid-to-liquid heat transfer and, compared to gas-fired appliances, a relatively low amount of heat to be transferred into the swimming pool water. 
     Gas-fired appliances with an air-to-liquid heat exchanger generally have a higher heat capacity than liquid-to-liquid heat exchangers. However, achieving adequate heat transfer using titanium tubes in the air-to-liquid heat exchanger of a gas-fired appliance has proven elusive in the swimming pool heater industry. One hurdle to attaining adequate heat transfer is the inability to extrude titanium into a tube with a substantial number of integrated fins. Although the extrusion process is widely used with copper and cupro-nickel in the industry, fins for a titanium tube cannot be extruded to the desired size for proper heat transfer. Some swimming pool heat exchangers include extruded fin tubes manufactured from either copper or cupro-nickel and have fin heights that cannot be manufactured out of titanium. 
     Some manufacturers have welded stainless steel fins to stainless steel tubing. Some industries, such as boiler and fluid processing, have used fins of a dissimilar material than the tube welded to the titanium tubes. Some swimming pool heat exchangers include plate fin designs with tubes mechanically expanded into collars on the plates to bond the fins and tubes. However, such methods are unfeasible for use with titanium. 
     Thus, a need exists for swimming pool heat exchangers that include titanium tubes with welded copper fins that provide the desired amount of heat transfer and corrosion resistance in air-to-liquid applications. These and other needs are addressed by the swimming pool heat exchangers and associated systems and methods of the present disclosure. 
     SUMMARY 
     In accordance with embodiments of the present disclosure, exemplary swimming pool heat exchangers are provided that include a housing and one or more tube assemblies disposed within the housing. Each of the tube assemblies includes an elongated titanium tube and at least one fin welded (e.g., laser welded) to an outer surface of the elongated titanium tube. In some embodiments, any type of welding can be used to attach the fins to the outer surface of the titanium tube. In some embodiments, the tube assemblies can include a plurality of fins individually welded in a spaced manner along the outer surface of the elongated titanium tube. In some embodiments, the tube assemblies can each include one fin fabricated as a single material and defining a helical shape such that the inner surface of the helical fin is continuously welded along the outer surface of the elongated titanium tube. The elongated titanium tube and the welded fin(s) allow for corrosion resistance to swimming pool water while simultaneously allowing for improved heat transfer from the heat exchanger to the swimming pool water. 
     The at least one fin can be a copper fin. The at least one fin can define a circular configuration. The elongated titanium tube can define a cylindrical configuration with an inner passage extending therethrough. The heat exchanger can include at least one tube sheet secured to ends of the one or more tube assemblies. 
     In some embodiments, the heat exchanger can include a column of the tube assemblies aligned along a central axis. In some embodiments, the heat exchanger can include a plurality of the tube assemblies staggered relative to each other. In some embodiments, the one or more tube assemblies can be of the same outer diameter. In some embodiments, the one or more tube assemblies can be of different outer diameters. In some embodiments, the one or more tube assemblies can be arranged in, e.g., a U-shaped or cylindrical configuration, a flat configuration defining a single column of tube assemblies, a bent spiral configuration, a cylindrical configuration including a passage extending between the tube assemblies, an A-shaped configuration, a V-shaped configuration, a solid block configuration including multiple rows and columns of tube assemblies disposed adjacent to each other, combinations thereof, or the like. 
     In accordance with embodiments of the present disclosure, an exemplary method of heating swimming pool water is provided. The method includes introducing heated gas (or an alternative source) into one of the exemplary heat exchangers disclosed herein. In particular, the heated gas can be introduced into an area surrounding the one or more tube assemblies. The method includes introducing or circulating swimming pool water to the one or more tube assemblies of the heat exchanger to allow for heat transfer between the heated gas and the swimming pool water. The method includes adjusting a configuration of the one or more tube assemblies within the housing to adjust a heat transfer rate to the swimming pool water. 
     In accordance with embodiments of the present disclosure, an exemplary heat exchanger system is provided that includes a heat exchanger as disclosed herein, a gas source, and a swimming pool water source. The gas source can be fluidly connected to the heat exchanger and configured to supply heated gas (or an alternative source) to an area surrounding the one or more tube assemblies. The swimming pool water source can be fluidly connected to the heat exchanger and configured to supply swimming pool water to the one or more tube assemblies. 
     Other objects and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To assist those of skill in the art in making and using the disclosed heat exchangers and associated systems and methods, reference is made to the accompanying figures, wherein: 
         FIG. 1  is a diagrammatic side view of an exemplary tube assembly of an exemplary heat exchanger according to the present disclosure. 
         FIG. 2  is a diagrammatic front view of an exemplary tube assembly of  FIG. 1 . 
         FIG. 3  is a perspective view of a plurality of exemplary tube assemblies of  FIG. 1 . 
         FIG. 4  is a front view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1 . 
         FIG. 5  is a front view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1 . 
         FIG. 6  is a front view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1 . 
         FIG. 7  is a front view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1 . 
         FIG. 8  is a front view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1 . 
         FIG. 9  is a front view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1 . 
         FIG. 10  is a front view of an exemplary heat exchanger including one column of a plurality of tube assemblies of  FIG. 1 . 
         FIG. 11  is a front view of an exemplary heat exchanger including two columns of a plurality of tube assemblies of  FIG. 1 . 
         FIG. 12  is a front view of an exemplary heat exchanger including three columns of a plurality of tube assemblies of  FIG. 1 . 
         FIG. 13  is a front view of an exemplary heat exchanger including two columns of a plurality of differently sized tube assemblies of  FIG. 1 . 
         FIG. 14  is a front view of an exemplary heat exchanger including one staggered column of a plurality of tube assemblies of  FIG. 1 . 
         FIG. 15  is a front view of an exemplary heat exchanger including two staggered columns of a plurality of tube assemblies of  FIG. 1 . 
         FIG. 16  is a front view of an exemplary heat exchanger including three staggered columns of a plurality of tube assemblies of  FIG. 1 . 
         FIG. 17  is a front view of an exemplary heat exchanger including two staggered columns and one aligned column of a plurality of differently sized tube assemblies of  FIG. 1 . 
         FIG. 18  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a horizontal cylindrical configuration. 
         FIG. 19  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a horizontal flat configuration. 
         FIG. 20  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a vertical flat configuration. 
         FIG. 21  is a perspective view of an exemplary heat exchanger including a tube assemblies of  FIG. 1  in a spiral configuration. 
         FIG. 22  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a vertical cylindrical configuration. 
         FIG. 23  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a flat A-shaped configuration. 
         FIG. 24  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a flat slanted configuration. 
         FIG. 25  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a solid block configuration. 
         FIG. 26  is a perspective view of an exemplary heat exchanger including a plurality of tube assemblies of  FIG. 1  in a flat slanted configuration. 
         FIG. 27  is a block diagram of an exemplary heat exchanger system according to the present disclosure. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In accordance with embodiments of the present disclosure, exemplary heat exchangers including a plurality of tubes with welded fins (e.g., laser welded) are provided. The tubes can be smooth titanium tubes that include copper fins welded to the exterior surface to enhance heat transfer from hot combustion gases to swimming pool water flowing within the heat exchanger tubes of a gas-fired pool heater. In some embodiments, the heat exchanger can include a single welded fin tube attached to a water circulating system suspended over a small source of heat. The exemplary heat exchangers achieve improved heat transfer by using titanium tubes with the welded copper fins in an air-to-liquid heat exchanger system with corrosion resistance (normally found in heat pump heat exchangers) and with a higher heat capacity of gas-fired appliances. In particular, the exemplary heat exchangers include titanium tubes in gas-fired swimming pool heaters to achieve corrosion resistance by isolating the swimming pool water within the titanium tubes, while maintaining the heat transfer characteristics of high-finned heat exchanger tubes. 
     By using titanium tubes with fins welded to the exterior made from copper or another material, heat transfer far above what titanium tubes can achieve alone can be accomplished while still offering the corrosion resistance needed in the portion of the heat exchanger in direct contact with swimming pool water. In particular, rather than using extruded or expanded fins as normally done in the swimming pool heater industry, the fins are welded to the titanium tube to facilitate the higher heat transfer than normally achieved by the titanium tubes alone. The welded fins, which provide a significant increase in surface area and are manufactured from a material with a higher thermal conductivity than titanium, thereby transferring the required amount of heat from a heat source, typically a burner, to swimming pool water inside of the titanium tube. The titanium tube, in turn, is resistant to corrosion typically caused by exposure to swimming pool water. This heat transfer is aided by the fact that the entire length of fin is welded to the tube, resulting in a permanent thermal bond between the titanium tube and the fins. The bond would not be permanent if the fin was only attached at the endpoints or only by mechanical means. Therefore, the thermal bond between the titanium tube and the fins results in an improved attachment between the components. 
     Although discussed herein with respect to gas-fired swimming pool heaters, it should be understood that the exemplary heat exchangers can be used with any appliance that includes a heat exchanger configured to transfer heat from hot combustion gases to liquid where corrosion caused by the liquid is one of the primary concerns. In some embodiments, the exemplary tubes and fins can be used in heaters for fluids, such as the heater for fluids disclosed in U.S. Pat. No. 6,026,804, incorporated herein by reference. In some embodiments, rather than laser welding, the titanium tube can be expanded into the plate fins. However, such methods are generally performed with larger and more complicated processing machines. 
     A plurality of titanium tubes can be arranged to form a heat exchanger and can be secured to one or more tube sheets to define the heat exchanger shape. The tube sheets provide a transition to the connected water system. In some embodiments, different geometries, configurations or arrangements of the heat exchanger can be used, resulting in different tube arrangements within the geometry and different airflow paths through the tubes. In some embodiments, varying sizes and/or numbers of the tubes can be used in flat horizontal or alternative configurations to differ airflow paths through the tubes. 
     In some embodiments, the material of the base tubing or the welded fins, or the geometry or arrangement of the fins relative to the tubes can be changed. Changing the fins, e.g., the height, material, fin density on the tube, combinations thereof, or the like, can allow for heat transfer at different rates. Thus, by changing characteristics of the fins welded to the tubes, the heat exchanger can be customized to adjust for the desired heat transfer rate. Changing the tube material can be used to accommodate for different types or sources of corrosion present in the heat exchanger system. 
     With reference to  FIGS. 1 and 2 , diagrammatic side and front views of an exemplary tube assembly  100  of an exemplary heat exchanger are provided. It should be understood that the heat exchanger can include one or more of the tube assemblies  100  arranged in various configurations depending on the heat transfer rate desired for the system. Each tube assembly  100  includes an elongated tube  102 , e.g., an extruded titanium tube defining a cylindrical configuration with an inner passage  103  extending therethrough configured to receive swimming pool water. In some embodiments, the tube  102  can define a configuration other than cylindrical, e.g., square, rectangular, oval, or the like. The tube  102  can define an overall length  104  extending along a central longitudinal axis  106 . The tube  102  can define an outer diameter  108  with a wall thickness  110 . In some embodiments, the outer diameter  108  can be approximately 0.75 inches and the wall thickness  110  can be approximately 0.02 inches. 
     The tube assembly  100  includes a plurality of fins  112  (e.g., copper fins) secured to an outer surface  116  of the tube  102 . The fins  112  can be welded (e.g., laser welded) to the outer surface  116  of the tube  102 . In particular, rather than only a partial welding, the entire circumferential inner diameter of the fins  112  can be laser welded to the outer surface  116  of the tube  102 . In some embodiments, the fins  112  can define a substantially circular configuration with a diameter  114 . In some embodiments, the diameter  114  of each fin  112  can be approximately, e.g., 40 mm, 50 mm, or the like. In some embodiments, each fin  112  can define a thickness between approximately 0.015 inches to approximately 0.020 inches. In some embodiments, the plurality of fins  112  can be fabricated as a single piece of material helically wound around the outer surface  116  of the tube  102  and welded along the entire contact surface of the inner surface of the fins  112  and the outer surface  116  of the tube  102 . Although illustrated as substantially circular, in some embodiments, the fins  112  can define different configurations, e.g., oval, rectangular, square, triangular, hexagonal, or the like. In some embodiments, fins  112  having multiple different configurations can be secured to the outer surface  116  of the tube  102 . For example, rather than being symmetrical relative to the vertical and horizontal central axes  128 ,  130  as shown in  FIG. 2 , the fins  112  can define an asymmetrical configuration. 
     In some embodiments, the fins  112  can be spaced substantially uniformly relative to each other along the tube  102 . In some embodiments, the spacing between the fins  112  can be different. In some embodiments, the fins  112  can be welded to the tube  102  such that the fins  112  extend substantially perpendicularly relative to the longitudinal axis  106 . In some embodiments, the fins  112  can be welded to the tube  102  at non-perpendicular angles relative to the longitudinal axis  106 . The fins  112  can extend only along a partial length  118  of the overall length  104  of the tube  102 . In particular, the proximal end  120  and the distal end  122  of the tube  102  can remain uncovered (e.g., without fins  112 ). For example, a proximal length  124  and a distal length  126  of the tube  102  can remain uncovered or exposed. In some embodiments, the proximal and distal lengths  124 ,  126  can be substantially similar in dimension. In some embodiments, the proximal and distal lengths  124 ,  126  can be different in dimension. 
       FIG. 3  shows a plurality of tube assemblies  100  positioned adjacent to each other. As shown in  FIG. 3 , the tube assemblies  100  can be aligned along the longitudinal axis  106  of each tube assembly  100  to form a substantially planar configuration of a heat exchanger. Alternative configurations or arrangements of the tube assemblies  100  will be discussed in greater detail below. 
       FIGS. 4-9  show front views of exemplary heat exchangers  150   a - f  with different configurations or arrangements of the tube assemblies  100  (referred to as primary tube assemblies  100   a  and secondary tube assemblies  100   b ). The diameter of the tube assemblies  100  defines the diameter of the fins of each respective tube assembly  100 . The tube assemblies  100   a ,  100   b  can be arranged in a pattern relative to each other and secured on opposing sides (e.g., the proximal and distal ends  120 ,  122 ) by endplates or tube sheets. In particular,  FIGS. 4-9  show different sizes and arrangements of the tube assemblies  100  that can fit within the same structure  152  that defines a height  154  and a width  156 . For example, different sizes and combinations of the tube assemblies  100  can be used to fit within a structure  152  that defines the width  156 . It should be understood that the tube assemblies  100  of  FIGS. 4-9  can include tube sheets disposed on each side of the tube assemblies  100   a ,  100   b . In some embodiments, the tube sheets can define a substantially rectangular configuration. 
     In the embodiment of  FIG. 4 , the primary tube assemblies  100   a  can be aligned along the horizontal central axis  130 . The primary tube assemblies  100   a  can be spaced relative to each other to receive the secondary tube assemblies  100   b  therebetween. In particular, the secondary tube assemblies  100   b  can be disposed between the primary tube assemblies  100   a  in a staggered or offset manner in a diagonal direction. The secondary tube assemblies  100   b  are therefore aligned along their respective horizontal central axes, with the horizontal central axis of the secondary tube assemblies  100   b  being offset from the horizontal central axis  130  of the primary tube assemblies  100   a . As an example, the heat exchanger  150   a  can include six tube assemblies  100   a ,  100   b . The fins of the tube assemblies  100   a ,  100   b  can be oriented substantially tangent relative to each other to avoid bypassed combustion gasses from escaping the heat exchanger. In some embodiments, each of the tube assemblies  100   a ,  100   b  can be spaced relative to each other such that no tube assemblies  100   a ,  100   b  are positioned directly against each other. In some embodiments, the fins of the tube assemblies  100   a ,  100   b  can be positioned adjacent to each other in an abutting relationship. 
     The heat exchanger  150   b  of  FIG. 5  can be substantially similar in structure and function to the heat exchanger  150   a  of  FIG. 4 , except that seven tube assemblies  100   a ,  100   b  can be used. In particular, the outer diameter of the fins of the tube assemblies  100   a ,  100   b  can be dimensioned smaller than the tube assemblies  100   a ,  100   b  of  FIG. 4 , allowing a greater number of tube assemblies  100   a ,  100   b  to fit within the same width  156  of the structure  152 . 
     The heat exchanger  150   c  of  FIG. 6  can be substantially similar in structure and function to the heat exchanger of  150   a  of  FIG. 4 , except that ten tube assemblies  100   a ,  100   b  can be used. In particular, the outer diameter of the fins of the tube assemblies  100   a ,  100   b  can be dimensioned smaller than the tube assemblies  100   a ,  100   b  of  FIGS. 4 and 5 , allowing a greater number of tube assemblies  100   a ,  100   b  to fit within the same width  156  of the structure  152 . 
     The heat exchanger  150   d  of  FIG. 7  can be substantially similar in structure and function to the heat exchanger  150   a  of  FIG. 4 , except that sixteen tube assemblies  100   a ,  100   b  can be used. In particular, the outer diameter of the fins of the tube assemblies  100   a ,  100   b  can be dimensioned smaller than the tube assemblies  100   a ,  100   b  of  FIGS. 4-6 , allowing a greater number of tube assemblies  100   a ,  100   b  to fit within the same width  156  of the structure  152 . 
     The heat exchanger  150   e  of  FIG. 8  can be substantially similar in structure and function to the heat exchanger  150   a  of  FIG. 4 , except that fourteen tube assemblies  100   a ,  100   b  can be used. In particular, the outer diameter of the fins of the tube assemblies  100   a ,  100   b  can be dimensioned smaller than the tube assemblies  100   a ,  100   b  of  FIGS. 4-6 , allowing a greater number of tube assemblies  100   a ,  100   b  to fit within the same width  156  of the structure  152 . 
     The heat exchanger  150   f  of  FIG. 9  can be substantially similar in structure and function to the heat exchanger  150   a  of  FIG. 4 , except that twelve tube assemblies  100   a ,  100   b  can be used. In particular, the outer diameter of the fins of the tube assemblies  100   a ,  100   b  can be dimensioned smaller than the tube assemblies  100   a ,  100   b  of  FIGS. 4-6 , allowing a greater number of tube assemblies  100   a ,  100   b  to fit within the same width  156  of the structure  152 . 
       FIGS. 10-17  are front views of exemplary heat exchangers  200   a - h  including a plurality of tube assemblies  100  arranged in different configurations. Each configuration provides a variation in heat transfer flow rates from the combustion gas to the swimming pool water. In particular, the different configurations result in varied heat transfer either by affecting the surface area in contact with the combustion gases (e.g., the number of rows and diameter of the tube assemblies  100 ) or by affecting the airflow pattern and distance the combustion gases stay in contact with the heat exchanger (e.g., staggered rows and diameter of the tube assemblies  100 ). For example,  FIG. 10  shows a heat exchanger  200   a  that includes a single column  204  of tube assemblies  100  of the same size (e.g., four tube assemblies). The tube assemblies  100  can be arranged to align along a vertical central axis  202 . Air flow can enter the heat exchanger  200   a  from, e.g., a first direction  206  substantially perpendicular to the vertical central axis  202 , a second direction  208  substantially aligned with the vertical central axis  202 , combinations thereof, or the like. 
       FIG. 11  shows a heat exchanger  200   b  that includes two columns  204   a ,  204   b  of tube assemblies  100  of the same size (e.g., each column including four tube assemblies). The tube assemblies  100  can be arranged such that four tube assemblies  100  are aligned along a first vertical central axis  202   a  and four tube assemblies  100  are aligned along a second vertical central axis  202   b , the first and second vertical central axes  202   a ,  202   b  being spaced from each other. The two columns  204   a ,  204   b  of the tube assemblies  100  can be disposed adjacent to each other. Further, the adjacently positioned tube assemblies  100  can be aligned along horizontal central axes  210   a - d . Air flow can enter the heat exchanger  200   b  from, e.g., a first direction  206  substantially perpendicular to the first and second vertical central axes  202   a ,  202   b , a second direction  208  substantially aligned with the first and second vertical central axes  202   a ,  202   b , combinations thereof, or the like. 
       FIG. 12  shows a heat exchanger  200   c  that includes three columns  204   a - c  of tube assemblies  100  of the same size (e.g., each column including four tube assemblies). The tube assemblies  100  can be arranged such that four tube assemblies  100  are aligned along a first vertical central axis  202   a , four tube assemblies  100  are aligned along a second vertical central axis  202   b , and four tube assemblies  100  are aligned along a third vertical central axis  202   c , the vertical central axes  202   a ,  202   b ,  202   c  being spaced from each other. The three columns  204   a - c  of the tube assemblies  100  can be disposed adjacent to each other. Further, the adjacently positioned tube assemblies  100  can be aligned along horizontal central axes  210   a - d . Air flow can enter the heat exchanger  200   c  from, e.g., a first direction  206  substantially perpendicular to the vertical central axes  202   a - c , a second direction  208  substantially aligned with the vertical central axes  202   a - c , combinations thereof, or the like. 
       FIG. 13  shows a heat exchanger  200   d  that includes two columns  204   a ,  204   b  of tube assemblies  100   a ,  100   b  of different sizes. The tube assemblies  100   a  of the same size can be arranged such that four tube assemblies  100   a  are aligned along a first vertical central axis  202   a , and two tube assemblies  100   b  of a size different from the tube assemblies  100   a  are aligned along a second vertical central axis  202   b . The first and second vertical central axes  202   a ,  202   b  are spaced from each other. In some embodiments, the each tube assembly  100   b  can be approximately double in diameter as compared to each tube assembly  100   a . The two columns  204   a ,  204   b  of the tube assemblies  100   a ,  100   b  can be disposed adjacent to each other. A horizontal central axis  212   a  of one of the tube assemblies  100   b  can be aligned between the horizontal central axes  210   a ,  210   b  of the tube assemblies  100   a . Similarly, a horizontal central axis  212   b  of the other tube assembly  100   b  can be aligned between the horizontal central axes  210   c ,  210   d  of the tube assemblies  100   a . Air flow can enter the heat exchanger  200   d  from, e.g., a first direction  206  substantially perpendicular to the vertical central axes  202   a ,  202   b , a second direction  208  substantially aligned with the vertical central axes  202   a ,  202   b , a third direction  214  substantially perpendicular to the vertical central axes  202   a ,  202   b  and opposing the first direction  206 , combinations thereof, or the like. 
       FIG. 14  shows a heat exchanger  200   e  that includes one staggered column  204  of tube assemblies  100  of the same size (e.g., the column including four tube assemblies). The tube assemblies  100  can be arranged such that every other tube assembly  100  is aligned along a first vertical central axis  202   a  and a second vertical central axis  202   b , respectively. The first and second vertical central axes  202   a ,  202   b  are spaced from each other. Each of the adjacently positioned tube assemblies  100  can be staggered by an angle relative to horizontal central axes  210   a - d . The fins of the tube assemblies  100  can be disposed in a substantially tangent and abutting configuration. Air flow can enter the heat exchanger  200   e  from, e.g., a first direction  206  substantially perpendicular to the vertical central axes  202   a ,  202   b , a second direction  208  substantially aligned with the vertical central axes  202   a ,  202   b , combinations thereof, or the like. 
       FIG. 15  shows a heat exchanger  200   f  that includes two staggered columns  204   a ,  204   b  of tube assemblies  100  of the same size (e.g., each column including four tube assemblies). The tube assemblies  100  can be arranged such that every other tube assembly  100  is aligned along a first to fourth vertical central axes  202   a - d , with two tube assemblies  100  aligned per vertical central axis  202   a - d . The vertical central axes  202   a - d  are spaced from each other. Each of the adjacently positioned tube assemblies  100  can be staggered by an angle relative to horizontal central axes  210   a - d . The fins of the tube assemblies  100  can be disposed in a substantially tangent and abutting configuration. For example, the fins of the tube assemblies  100  aligned along the horizontal central axes  210   a - d  can abut each other. Air flow can enter the heat exchanger  200   f  from, e.g., a first direction  206  substantially perpendicular to the vertical central axes  202   a - d , a second direction  208  substantially aligned with the vertical central axes  202   a - d , combinations thereof, or the like. 
       FIG. 16  shows a heat exchanger  200   g  that includes three staggered columns  204   a - c  of tube assemblies  100  of the same size (e.g., each column including four tube assemblies). The tube assemblies  100  can be arranged such that every other tube assembly  100  is aligned along a first to sixth vertical central axes  202   a - f , with two tube assemblies  100  aligned per vertical central axis  202   a - f . The vertical central axes  202   a - f  are spaced from each other. Each of the adjacently positioned tube assemblies  100  can be staggered by an angle relative to horizontal central axes  210   a - d . The fins of the tube assemblies  100  can be disposed in a substantially tangent and abutting configuration. For example, the fins of the tube assemblies  100  aligned along the horizontal central axes  210   a - 3  can abut each other. Air flow can enter the heat exchanger  200   g  from, e.g., a first direction  206  substantially perpendicular to the vertical central axes  202   a - f , a second direction  208  substantially aligned with the vertical central axes  202   a - f , combinations thereof, or the like. 
       FIG. 17  shows a heat exchanger  200   h  that includes one staggered column  204   a  of tube assemblies  100   a  of the same size (e.g., the column including four tube assemblies) and one column  204   b  of tube assemblies  100   b  sized differently than the tube assemblies  100   a . The tube assemblies  100   a  can be arranged such that every other tube assembly  100  is aligned along a first vertical central axis  202   a  and a second vertical central axis  202   b , respectively. The first and second vertical central axes  202   a ,  202   b  are spaced from each other. Each of the adjacently positioned tube assemblies  100   a  can be staggered by an angle relative to horizontal central axes  210   a - f . The tube assemblies  100   b  can be arranged such that the two tube assemblies  100   b  are aligned along a third vertical central axis  202   c . The tube assemblies  100   b  can be aligned with respective horizontal central axes  210   b ,  210   e  of two tube assemblies  100   a . In some embodiments, the tube assemblies  100   b  can be disposed along horizontal central axes that are parallel to (but not aligned with) the horizontal central axes  210   a - f ). The fins of the tube assemblies  100   a ,  100   b  can be disposed in a substantially tangent and abutting configuration. Air flow can enter the heat exchanger  200   h  from, e.g., a first direction  206  substantially perpendicular to the vertical central axes  202   a - c , a second direction  208  substantially aligned with the vertical central axes  202   a - c , a third direction  214  substantially perpendicular to the vertical central axes  202   a - c  and opposing the first direction  206 , combinations thereof, or the like. 
       FIGS. 18-26  show perspective views of exemplary heat exchangers  250   a - i  including tube assemblies  100  in different configurations. Although illustrated as substantially square or rectangular in cross-section, in some embodiments, the tube assemblies  100  can have a substantially round cross-section (such as the tube assemblies of  FIGS. 1-17 ). For example,  FIG. 18  shows a heat exchanger  250   a  including a plurality of tube assemblies  100  stacked and aligned relative to each other, and bent into a substantially U-shaped, tear-shaped or horizontal cylindrical configuration. The tube assemblies  100  can extend in a direction substantially aligned with horizontal. The ends of the tube assemblies  100  can be disposed adjacent to each other and secured to a single tube sheet  252 . Due to the curved shape of the tube assemblies  100 , a passage  254  is formed between the tube assemblies  100  and extends the height of the heat exchanger  250   a . Air flow can enter into the passage  254  from above 256 and below 258. Air flow can enter/exit the heat exchanger  250   a  in opposing directions  260 ,  262  perpendicular to the tube assemblies  100 . 
       FIG. 19  shows a heat exchanger  250   b  including a plurality of tube assemblies  100  aligned relative to each other and forming a substantially horizontal flat configuration (e.g., a single row of tube assemblies  100 ). Particularly, the tube assemblies  100  can extend in a direction substantially aligned with horizontal. The ends of the tube assemblies  100  can be aligned and secured to tube sheets  252   a ,  252   b  on opposing sides of the tube assemblies  100 . Air flow can enter/exit the heat exchanger  250   b  in opposing directions  256 ,  258  perpendicular to the tube assemblies  100 . 
       FIG. 20  shows a heat exchanger  250   c  including a plurality of tube assemblies  100  aligned relative to each other and forming a substantially vertical flat configuration (e.g., a single column of tube assemblies  100 ). In particular, the tube assemblies  100  in the vertical configuration can be aligned substantially perpendicular to the alignment of the horizontal configuration, and substantially perpendicular to horizontal. The ends of the tube assemblies  100  can be aligned and secured to tube sheets  252   a ,  252   b  on opposing sides of the tube assemblies  100 . Air flow can enter/exit the heat exchanger  250   c  in opposing directions  256 ,  258  perpendicular to the tube assemblies  100 . 
       FIG. 21  shows a heat exchanger  250   d  including a single tube assembly  100  curved into a spiral configuration. In particular, the tube assembly  100  can be bent into a spiral shape with the ends of the tube assembly  100  being secured to tube sheets  252   a ,  252   b  sized for only a single tube assembly  100 . The spiral configuration results in a passage  254  formed between the tube assembly  100  components and extending the height of the heat exchanger  250   d . Air flow can enter/exit the heat exchanger  250   d  in opposing directions  256 ,  258  perpendicular to the tube assembly  100 , via a direction  260  passing through the passage  254 , combinations thereof, or the like. 
       FIG. 22  shows a heat exchanger  250   e  including a plurality of tube assemblies  100  disposed adjacent to each other and curved into a vertical cylindrical configuration (e.g., a curved single row of tube assemblies  100  extending substantially perpendicularly to horizontal). In particular, due to the cylindrical configuration of the tube assemblies  100 , a passage  254  is formed between the tube assemblies  100  and extends the height of the heat exchanger  250   e . The ends of the tube assemblies  100  can be aligned and secured to tube sheets  252   a ,  252   b . Air flow can enter/exit the heat exchanger  250   e  in opposing directions  256 ,  258  perpendicular to the tube assemblies  100 , via a direction  260  passing through the passage  254 , combinations thereof, or the like. 
       FIG. 23  shows a heat exchanger  250   f  including a plurality of tube assemblies  100   a ,  100   b  aligned and formed into a substantially flat A-shaped or upside down V-shaped configuration. In particular, the heat exchanger  250   f  includes a first flat group of tube assemblies  100   a  and a second flat group of tube assemblies  100   b  that are joined at one central tube assembly  100 . The first and second flat group of tube assemblies  100   a ,  100   b  connect at the central tube assembly  100  and extend in opposing directions to form an angle  264  therebetween (e.g., between approximately 30° and approximately 90°, or the like). Each of the tube assemblies  100   a ,  100   b  can extend substantially parallel to horizontal. The ends of the tube assemblies  100   a ,  100   b  can be aligned and secured to tube sheets  252   a ,  252   b  on opposing sides of the tube assemblies  100   a ,  100   b . Air flow can enter/exit the heat exchanger  250   f  via direction  256  perpendicular to the second flat group of tube assemblies  100   b , direction  258  perpendicular to the first flat group of tube assemblies  100   a , via direction  260  perpendicular to the central tube assembly  100 , combinations thereof, or the like. 
       FIG. 24  shows a heat exchanger  250   g  including a plurality of tube assemblies  100  aligned and formed into a flat slanted configuration (e.g., a single row of tube assemblies  100  each extending substantially parallel to horizontal, with the combined row of tube assemblies  100  being slanted relative to horizontal). In particular, the tube assemblies  100  can be disposed adjacent to each other and aligned into a flat configuration, and the heat exchanger  250   g  can be slanted by an angle  264  (e.g., between approximately 30° and approximately 90°) relative to a horizontal plane  266 . The ends of the tube assemblies  100  can be aligned and secured to tube sheets  252   a ,  252   b  on opposing sides of the tube assemblies  100 . In the orientation of  FIG. 24 , the tube sheets  252   a ,  252   b  are at the sides of the heat exchanger  250   g . Air flow can enter/exit the heat exchanger  250   g  via direction  256  parallel to the horizontal plane  266 , via direction  258  perpendicular to the horizontal plane  266 , combinations thereof, or the like. 
     While the above configurations were formed from a single column of tube assemblies  100 ,  FIG. 25  shows a heat exchanger  250   h  including a plurality of tube assemblies  100  aligned and formed into a solid block configuration. In particular, the tube assemblies  100  can be disposed adjacent to each other in multiple rows and columns to form the solid block configuration. Each of the tube assemblies  100  can extend substantially parallel to horizontal. It should be understood that a variety of shapes can be formed by varying the number of rows and columns of the heat exchanger  250   h . The ends of the tube assemblies  100  can be aligned and secured to tube sheets  252   a ,  252   b  on opposing sides of the tube assemblies  100 . Air flow can enter/exit the heat exchanger  250   h  via direction  256  perpendicular to the tube assemblies  100 . 
       FIG. 26  shows a heat exchanger  250   i  including a plurality of tube assemblies  100  aligned and formed into a flat slanted configuration (e.g., a single row of aligned tube assemblies  100 , with each tube assembly  100  extending at an angle relative to horizontal). In particular, the tube assemblies  100  can be disposed adjacent to each other and aligned into a flat configuration, and the heat exchanger  250   i  can be slanted by an angle  264  (e.g., between approximately 30° and approximately 90°) relative to a horizontal plane  266 . The ends of the tube assemblies  100  can be aligned and secured to tube sheets  252   a ,  252   b  on opposing sides of the tube assemblies  100 . In the orientation of  FIG. 26 , the tube sheets  252   a ,  252   b  are substantially at the top and bottom of the heat exchanger  250   i . The tube sheets  252   a ,  252   b  can be substantially perpendicular to the ends of the tube assemblies  100 , and angled relative to the horizontal plane  266 . Air flow can enter/exit the heat exchanger  250   i  via direction  256  parallel to the horizontal plane  266 , via direction  258  perpendicular to the horizontal plane  266 , combinations thereof, or the like. 
       FIG. 27  is a block diagram of an exemplary heat exchanger system  300 . The heat exchanger system  300  can include at least one of the exemplary heat exchangers  302  described herein. The heat exchanger  302  includes one or more tube assemblies  304 . The heat exchanger  302  can be disposed within a heater housing  306 . A gas source  308  can be fluidly connected to the heater housing  306  and/or the heat exchanger  302  to introduce heated gas into an area surrounding the tube assemblies  304 . A water circulating system or source  310  can be fluidly connected to the heater housing  306  to introduce swimming pool water into the tube assemblies  304 . Due to the heated gas surrounding the tube assemblies  304 , the swimming pool water can be heated to the desired temperature. As noted above, the titanium structure of the elongated tubes with the copper fins welded to the tubes provides for corrosion resistance by isolating the swimming pool water within the tubes, while allowing for improved heat transfer to the swimming pool water. 
     While exemplary embodiments have been described herein, it is expressly noted that these embodiments should not be construed as limiting, but rather that additions and modifications to what is expressly described herein also are included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention.