Heat exchange array

Abstract

A heat exchange array arranged to be used in a heat exchange unit and further arranged to recover energy from an exhaust gas, comprising: a first heat exchange tube and a second heat exchange tube, each arranged to carry a heat exchange medium and further each comprising a series of external fins; and wherein the first heat exchange tube comprises a left-handed helically coiled tube having an first elastic stress, and the second heat exchange coil comprises a right-handed helically coiled tube having a second elastic stress, and wherein the first and second heat exchange tubes are interconnected such that the first elastic stress opposes the second elastic stress.

1 . A heat exchange array arranged to be used in a heat exchange unit and further arranged to recover energy from an exhaust gas, comprising:
 a first heat exchange tube and a second heat exchange tube, each arranged to carry a heat exchange medium and further each comprising a series of external fins; and   wherein the first heat exchange tube comprises a left-handed helically coiled tube having an first elastic stress, and the second heat exchange coil comprises a right-handed helically coiled tube having a second elastic stress,   and wherein the first and second heat exchange tubes are interconnected such that the first elastic stress opposes the second elastic stress.   
     
     
         2 . A heat exchange array according to  claim 1  wherein the first and second heat exchange tubes are interconnected via a support member arranged to hold the helically coiled tubes in a fixed shape. 
     
     
         3 . A heat exchange array according to  claim 2  wherein the support member comprises at least one support bracket defining apertures arranged to receive each turn of the helically coiled tubes. 
     
     
         4 . A heat exchange array according to  claim 3  wherein the or each support member has a length along the circumferential direction of the coils of the array such that the or each support member supports a plurality of fins. 
     
     
         5 . A heat exchange array according to  claim 1 , further comprising a header connected to an end region of the first and an end region of the second heat exchange tubes, the header arranged to provide an input or output for a heat exchange medium into the tubes. 
     
     
         6 . A heat exchange array according to  claim 5  wherein the first and second heat exchange tubes are connected to the header from opposing directions. 
     
     
         7 . A heat exchange array according to  claim 1  wherein the first heat exchange tube has substantially the same length as the second heat exchange tube. 
     
     
         8 . A heat exchange array according to  claim 1  wherein the first heat exchange tube comprises a left-handed helically coiled tube having a first pitch and second heat exchange tube comprises a right-handed helically coiled tube having a second pitch, wherein the first pitch is not equal to the second pitch. 
     
     
         9 . A heat exchange array according to  claim 1  wherein the first heat exchange tube and the second heat exchange tube are arranged co-axially. 
     
     
         10 . A heat exchange array according to  claim 1  wherein the first heat exchange tube surrounds the second heat exchange tube, or vice versa. 
     
     
         11 . A heat exchange array according to  claim 10 , further comprising a plurality of first and/or second heat exchange tubes arranged into a plurality of concentric layers. 
     
     
         12 . A heat exchange array according to  claim 11  wherein each of the concentric layers comprises a plurality of left-handed helically coiled tubes each having the same radius of curvature, or a plurality of right-handed helically coiled tube tubes each having the same radius of curvature. 
     
     
         13 . A heat exchange array according to  claim 11  wherein the concentric layers alternate between comprising first heat exchange tubes and comprising second heat exchange tubes. 
     
     
         14 . A heat exchange array according to  claim 1  comprising an equal number of first and second heat exchange tubes. 
     
     
         15 . A heat exchange array according to  claim 1  wherein the first and second heat exchange tubes are circular in cross section, and have a diameter of approximately between 21 mm and 168 mm. 
     
     
         16 . A heat exchange array according to  claim 1  wherein the radius of curvature of the left-handed helically coiled tube and right-handed helically coiled tube is between 1 m and 4 m. 
     
     
         17 . A heat exchange unit comprising the heat exchange array of  claim 1 . 
     
     
         18 . A method of manufacturing a heat exchange array comprising a plurality of heat exchange tubes, which each heat exchange tube comprising a plurality or external fins, using a rotatable mandrel, the method comprising the steps of:
 (a) providing at least one first support member on a roller portion of the mandrel to receive a first heat exchange tube;   (b) holding one end of a first heat exchange tube to the first support member;   (c) rotating the roller, whilst feeding the first heat exchange tube along a length of the roller in a first direction to form the first heat exchange tube into a first helical coil;   (d) attaching a second support member, arranged to receive a second heat exchange tube, to the first support member;   (e) holding one end of the second heat exchange tube to the second support member; and   (f) rotating the roller in the same direction, whilst feeding the second heat exchange tube along a length of the roller in a second direction to form the second heat exchange tube into a second helical coil, wherein the first direction is opposite to the second direction such that first helical coil is of opposite chirality to the second helical coil.   
     
     
         19 . A method of manufacturing a heat exchange array according to  claim 18  wherein the method further comprises repeating steps (a) to (f) to provide a heat exchange array comprising a plurality of the first and/or the second heat exchange coils in a plurality of concentric layers. 
     
     
         20 . A method of manufacturing a heat exchange array according to  claim 18  wherein step (b) comprises holding a plurality of first heat exchange tubes to the first support member so that each concentric layer comprises a plurality of first heat exchange coils. 
     
     
         21 . A method of manufacturing a heat exchange array according to  claim 18  wherein step (e) comprises holding a plurality of second heat exchange tubes to the second support member so that each concentric layer comprises a plurality of second heat exchange coils. 
     
     
         22 . A method of manufacturing a heat exchange array according to  claim 18  in which shims are placed at intermediate positions between support members as the tubes are wound.