Advanced gravity-film & double-helix heat exchangers ("gfx+™ & "dhx™")

Abstract

This invention teaches how to reduce the copper content of a commercially available, all-copper, double-wall-vented, coil & tube Gravity Film Heat Exchangers (“GFX”) developed for the GFX™ system of U.S. Pat. No. 4,619,311. For example, a GFX+™ equivalent of a residential Model G3-60 GFX can be made using 71% less copper. Such significant copper-savings, with comparable heat transfer coefficient (“U”), effectiveness and coil pressure drop, is achieved by improvements in innovations disclosed in Provisional Patent Application 60/709,889 (Filing date: Aug. 22, 2005). Unlike conventional, single and multi-coil GFX's currently produced by several manufacturers, the present invention enables the use of a variety of metal and/or plastic components to achieve either single or vented-double-wall construction and lower manufacturing costs. In fact, higher U-values can be achieved by increasing the potable-water pressure drop of a GFX+ equivalent of any coil & tube GFX. The present invention also teaches how to simultaneously optimize U-values & pressure drop[s] and means of introducing controlled turbulence & mixing. Such trade-offs cannot be achieved in a conventional GFX design having one or more coils wound singly or in parallel. It also teaches how to manufacture an improved version of the Double-Helix Heat Exchanger (“DHX”), which is also disclosed in said Provisional Patent Application 60/709,889. Unlike a GFX, which must be installed vertically for best effectiveness, a DHX can be operated in any orientation. For applications permitting higher pressure drop, a DHX can be designed with a much higher U-value than a comparable GFX or GFX+.

1 . The apparatus shown  FIG. 1(   a ) and illustrated in  FIGS. 1(   b )( c )( d )( e ), comprised of a single-wall or double-wall tube having a tightly wrapped helical-fin to increase its “collapse pressure”. 
   
   
       2 . The apparatus of  claim 1  having a tightly wrapped helical-fin with a non-uniform or staggered pitch to promote turbulence, mixing, and control the pressure drop encountered by a fluid or gas constrained to flow in the helical channel formed by said tube and helical-fin by an outer shell made of metal or plastic as shown in  FIG. 1(   a )( b ). 
   
   
       3 . The apparatus of  claim 2  having a tight-fitting outer jacket having inlet/outlet connectors and pressure seals so as to cause to a first fluid or gas entering said inlet connector to flow in a helical path between the fins of said helical-fin and against the outer wall of said tube to promote efficient heat transfer to a second fluid or gas flowing in thermal contact with the inner wall of said tube before exiting said outlet connector. 
   
   
       4 . The apparatus of  claim 3  mounted in a vertical position to cause a falling-film to flow down the inner wall of said tube, or in the alternative, the apparatus of  claim 1  formed to fit inside said tube to form a “DHX” having two helical flow paths. 
   
   
       5 . The apparatus of  claim 4  having said first and second fluids (or gas) flowing in opposite (contra-flow) directions for best heat transfer effectiveness. 
   
   
       6 . The apparatus of  claim 5  having more than one helical fin to form parallel flow paths. 
   
   
       7 . The apparatus of  claim 6  having a double-wall tube formed by wrapping the outer surface of the larger single-wall tube with a metal foil thin enough to be held in intimate thermal-contact with said single-wall tube whenever said helical flow path is pressurized. 
   
   
       8 . The apparatus of  claim 7  wherein a vent is formed by overlapping said metal foil to form a leak-proof lap joint by soldering, seam welding or other fastening process. 
   
   
       9 . The apparatus of  claim 8  having more than one vent either machined into said inner tube or created by multiple lap joints.