Heat exchanger and use thereof in showers

Abstract

An improved heat exchanger design is disclosed. The design of the heat exchanger provides for a safe separation of the flow streams even in the event of leakage. An improved heat recovery device for use in the drain conduit of standard shower installations, comprising the heat exchanger of the invention, is also disclosed.

1 . A heat recovery device adapted for use in the drain conduit of a shower installation having a hot water supply line, a cold water supply line, a means for mixing water from both said lines to deliver water at a suitable temperature to a shower head, and a drain conduit for disposing of waste water passing out of the shower installation, the heat recovery device transferring heat from the waste water to the cold water supply before it enters said mixing means, said heat recovery device comprising: 
 A. a section of generally tubular first conduit formed of a material having a relatively high degree of heat conductivity, said first conduit having an inlet end connected to an upstream portion of said drain conduit and an outlet end connected to a downstream portion of said drain conduit so that waste water passing through said drain conduit also passes through said first conduit, said inlet and outlet ends of said first conduit being connected to said upstream and downstream portions respectively of said drain conduit in such a manner that said first conduit between said inlet and outlet ends is disposed at a lower level than said inlet and outlet ends so that said first conduit remains filled with water at all times and functions as a water trap, and contains at least one helical convolution formed in the wall of said first conduit.    B. conduit means connected into said cold water line of said shower equipment and being thermally operatively associated with said first conduit such that cold water passes through said conduit means while passing through said cold water line to be exposed to heat from said first conduit from waste water passing therethrough, said conduit means comprising a second conduit formed of a material having a relatively high degree of heat conductivity, said second conduit being disposed in intimate heat exchange relationship with said first conduit, said second conduit having an inlet end connected to an upstream portion of said cold water line and an outlet end connected to a downstream portion of said cold water line so that cold water passing through said cold water line also passed through said second conduit and receives heat transferred to said first conduit from said waste water, said second conduit having an inner wall that comprises a layer of thermally conductive material that conforms generally to the said helically convoluted outer surface of said first conduit, said second conduit having an outer wall consisting of a substantially tubular member that fits closely to the largest diameter parts of said convoluted inner wall and is suitably joined to it, so that the second conduit is comprised of the helical lumen formed between said outer and said inner walls, said outer wall containing at least one opening at each end of the helical lumen for inlet and exit flow respectively of said cold water supply suitable for adapting to common plumbing fittings,    whereby heat from said waste water is conducted through said first conduit means to pre-heat cold water passing through said second conduit means before reaching said mixing means.    
   
   
       2 . The heat recovery device of  claim 1  wherein said first conduit is substantially straight and generally horizontal, said inlet and said outlet ends are disposed at substantially 90 degrees to said first conduit means, and disposed substantially vertically.  
   
   
       3 . The heat recovery device of  claim 2  wherein two assemblies of said first conduits and said conduit means are connected in series using a 180 degree conduit section to join them, and are arranged substantially parallel to each other in the generally horizontal plane, and said inlet end of the upstream section and the exit ends of the downstream section of the first conduit sections are disposed in a substantially vertical plane, so that they are parallel to each other and in close proximity to each other.  
   
   
       4 . The heat recovery device of  claim 1  wherein said first conduit forms a loop in the generally horizontal plane, or at a small angle to the horizontal plane, said inlet and outlet ends disposed in relative close proximity to each other, said inlet and said outlet ends disposed at substantially 90 degrees to said first conduit means, said inlet and outlet ends disposed substantially vertically.  
   
   
       5 . The heat recovery device of  claim 1 , wherein a spacer material is located between the outer surface of the first conduit and the outer surface of the inner wall of the second conduit.  
   
   
       6 . The heat recovery device of  claim 5 , wherein the spacer material is selected from the group consisting of high temperature fibrous material, metal mesh, metal wire, glass fibers, carbon fibers, aramid fibers, and ceramic fibers.  
   
   
       7 . A heat exchanger for transferring heat between a first liquid and a second liquid, comprising: 
 A. a section of generally tubular first conduit for conducting a first liquid, having at least one helical convolution formed in its wall; and    B. a second conduit being thermally operatively associated with said first conduit, said second conduit being disposed in intimate heat exchange relationship with said first conduit, said second conduit having a convoluted inner wall that comprises a layer of thermally conductive material that conforms generally to the outer surface of said helically convoluted first conduit, said second conduit having an outer wall consisting of a substantially tubular member that fits closely to the largest diameter parts of said convoluted inner wall and is suitably joined to it, so that the second conduit is comprised of the helical lumen formed between said outer and said inner walls, said outer wall containing at least one opening at each end of the helical lumen for inlet and exit flow of the second liquid, respectively.    
   
   
       8 . The heat exchanger of  claim 7 , wherein a spacer material is located between the outer surface of the first conduit and the outer surface of the inner wall of the second conduit.  
   
   
       9 . The heat exchanger of  claim 8 , wherein the spacer material is selected from the group consisting of metal mesh, metal wire, glass fibers, carbon fibers, aramid fibers, and ceramic fibers.  
   
   
       10 . The heat exchanger of  claim 7 , wherein at least one of the outer surface of the first conduit and the outer surface of the inner wall of the second conduit, is grooved or textured.  
   
   
       11 . The heat exchanger of  claim 7 , wherein a space is located between the outer surface of the wall of the first conduit and the outer surface of the inner wall of the second conduit, said space being in gaseous or liquid communication with the surrounding environment, said space providing a means for accidental leakage of the first or second liquid to escape.  
   
   
       12 . The heat exchanger of  claim 7 , wherein first and second conduits are formed of a material having a relatively high degree of heat conductivity.  
   
   
       13 . The heat exchanger of  claim 7 , wherein the inner diameter of the first conduit is between about 0.5 and about 8 inches, between about 1 and about 6 inches, between about 1.5 and about 2 inches, between about 2 and about 3 inches, between about 3 and about 4 inches, or larger than about 8 inches.  
   
   
       14 . The heat exchanger of  claim 7 , wherein the inner diameter of the second conduit is about 25 to about 50%, about 15 to about 25%, or about 5 to about 15% of the diameter of the inner diameter of the first conduit.  
   
   
       15 . The heat exchanger of  claim 7 , wherein the pitch of the helical convolutions is about 0.2 to about 12 inches, about 1 to about 8 inches, about 3 to about 6 inches, about 2 to about 3 inches, about 1.2 to about 3.5 inches, or about 1 to about 2 inches.  
   
   
       16 . The heat exchanger of  claim 7 , wherein the first conduit has two, three, four or more helical convolutions.  
   
   
       17 . A heat recovery device for use in a personal shower installation, said heat recovery device comprising the heat exchanger of  claim 7 , wherein said first liquid corresponds to waste water passing out of the shower installation, and said second liquid corresponds to a cold water supply.  
   
   
       18 . A heat recovery device adapted for use in the drain conduit of a shower installation having a hot water supply line, a cold water supply line, a means for mixing water from both said lines to deliver water at a suitable temperature to a shower head, and a drain conduit for disposing of waste water passing out of the shower installation, the heat recovery device transferring heat from the waste water to the cold water supply before the cold water supply enters said mixing means, said heat recovery device comprising the heat exchanger of  claim 7 , wherein the first liquid corresponds to waste water passing out of the shower installation, and the second liquid corresponds to the cold water supply.  
   
   
       19 . The heat exchanger of  claim 7  herein the helical convolutions in the wall of the first conduit impart turbulence to the first liquid.  
   
   
       20 . The heat exchanger of  claim 7  whereby a hydroforming process is used to simultaneously form the first conduit and said inner wall of the second conduit.