Heat Exchanger for Drain Heat Recovery

Abstract

A heat exchanger includes an upright center tube for connection to a drain line and an outer tube surrounding the upright center tube so as to define an annular space for connection to a supply line. Baffle portions are received within the annular space between the upright center tube and the outer tube and so as to be arranged to induce turbulence in the annular space while permitting the flow to remain in a substantially axial direction of the tubes. Sleeves may be used to connect the ends of the outer tube to the center tube so as to define a single wall portion of the center tube between the sleeves and double wall portions of the center tube where the center tube is overlapped by the sleeves such that the double wall portions are open axially outwardly and externally at the end of the outer tube.

1 . A heat exchanger for use between a drain line having a first fluid flow therethrough and a supply line having a second fluid flow therethrough, the heat exchanger comprising:
 an upright center tube extending longitudinally between opposing top and bottom ends;   the upright center tube being arranged for connection to the drain line so as to receive the first fluid flow longitudinally through the upright center tube;   an outer tube surrounding the upright center tube so as to define an annular space between upright center tube and the outer tube which spans longitudinally along the upright center tube between opposing top and bottom ends of the outer tube;   the outer tube being arranged for connection to the supply line so as to be arranged to receive the second fluid flow longitudinally through the annular space between the upright center tube and the outer tube; and   a plurality of baffle portions received within the annular space between the upright center tube and the outer tube and so as to be arranged to induce turbulence in the second fluid flow while permitting the second fluid flow to remain in a substantially axial direction of the tubes.   
     
     
         2 . The heat exchanger according to  claim 1  wherein the baffle portions comprises wire members received in the annular space which have a diameter which is equal to or less than half a radial dimension of the annular space. 
     
     
         3 . The heat exchanger according to  claim 2  wherein the wire members are wound helically about the center tube. 
     
     
         4 . The heat exchanger according to  claim 2  wherein the wire members include a first wire member wound helically about the center tube in a first direction and a second wire member wound helically about the center tube in a second direction opposite to the first direction such that the first and second wire members overlap and intersect one another in a crosswise manner at a plurality of locations axially spaced along the center tube. 
     
     
         5 . The heat exchanger according to  claim 1  wherein the baffle portions comprise protrusions formed on at least one of the upright center tube or the outer tube so as to project into the annular space between the upright center tube and the outer tube and so as to be arranged to induce turbulence in the second fluid flow. 
     
     
         6 . The heat exchanger according to  claim 5  wherein the protrusions are arranged to span only partway across the annular space between the upright center tube and the outer tube. 
     
     
         7 . The heat exchanger according to  claim 5  wherein the protrusions are formed on an inner surface of the outer tube and extend generally radially inwardly towards the center tube. 
     
     
         8 . The heat exchanger according to  claim 5  wherein the protrusions are formed on an outer surface of the center tube and extend generally radially outwardly towards the outer tube. 
     
     
         9 . The heat exchanger according to  claim 5  wherein the protrusions comprise annular ribs which are longitudinally spaced apart. 
     
     
         10 . The heat exchanger according to  claim 5  wherein the protrusions are formed on both an outer surface of the center tube and an inner surface of the outer tube so as to project into said annular space. 
     
     
         11 . The heat exchanger according to  claim 1  wherein at least one outer end of the outer tube is joined to the center tube by an auxiliary sleeve supported about the center tube so as to define a double wall portion of the center tube at the auxiliary sleeve and a single wall portion of the center tube at an intermediate location between opposing ends of the outer tube which is not overlapped by the auxiliary sleeve, the auxiliary sleeve being joined to the outer tube at a location which is spaced axially outward in relation to a connection between the between the auxiliary sleeve and the center tube. 
     
     
         12 . The heat exchanger according to  claim 11  wherein both ends of the outer tube are joined to the center tube by an auxiliary sleeve such that the single wall portion is defined between the auxiliary sleeves. 
     
     
         13 . The heat exchanger according to  claim 11  wherein an annular space between the center tube and the auxiliary sleeve at the double wall portion is open axially outwardly and externally of the center tube at the outer end of the outer tube. 
     
     
         14 . The heat exchanger according to  claim 11  wherein the single wall portion is longer in an axial direction than the double wall portion. 
     
     
         15 . The heat exchanger according to  claim 11  wherein the auxiliary sleeve portion is thinner in radial thickness than the single wall portion of the center tube. 
     
     
         16 . The heat exchanger according to  claim 11  wherein the center tube is thinner in radial thickness at the double wall portion than at the single wall portion thereof. 
     
     
         17 . The heat exchanger according to  claim 11  wherein the auxiliary sleeve protrudes axially outward beyond the respective outer end of the outer tube. 
     
     
         18 . The heat exchanger according to  claim 11  wherein the center tube protrudes axially outward beyond an outer end of the auxiliary sleeve. 
     
     
         19 . The heat exchanger according to  claim 11  wherein the end of the center tube is enlarged in inner diameter at an end portion overlapped by an outer end of the auxiliary sleeve and the outer end of the outer tube such that the end portion is arranged to receive a portion of a drain line therein having an outer diameter which is substantially equal to an outer diameter of the single wall portion. 
     
     
         20 . A heat exchanger for use between a drain line having a first fluid flow therethrough and a supply line having a second fluid flow therethrough, the heat exchanger comprising:
 an upright center tube extending longitudinally between opposing top and bottom ends;   the upright center tube being arranged for connection to the drain line so as to receive the first fluid flow longitudinally through the upright center tube;   an outer tube surrounding the upright center tube so as to define an annular space between upright center tube and the outer tube which spans longitudinally along the upright center tube between opposing top and bottom ends of the outer tube;   the outer tube being arranged for connection to the supply line so as to be arranged to receive the second fluid flow longitudinally through the annular space between the upright center tube and the outer tube; and   at least one auxiliary sleeve supported about the center tube and joining a respective outer end of the outer tube to the center tube so as to define a double wall portion of the center tube at the auxiliary sleeve and a single wall portion of the center tube at an intermediate location between opposing ends of the outer tube which is not overlapped by said at least one auxiliary sleeve;   said at least one auxiliary sleeve being joined to the outer tube at a location which is spaced axially outward in relation to a connection between the between the auxiliary sleeve and the center tube; and   the double wall portion of said at least one auxiliary sleeve being open axially outwardly and externally of the center tube at the respective outer end of the outer tube.