Method for extracting heat from an effluent flowing in a duct, heat exchanger and system for carrying out such a method

Abstract

Method for extracting heat from an effluent flowing in a duct ( 2 ), in particular a wastewater collection device. In said method, a heat exchanger (E) that is submerged in the effluent is mounted at least on the bottom of the duct, the heat exchanger (E) being formed by coating tubes ( 3 ) with a material that is sufficiently heat-conducting, is poured around the tubes, and hardens in situ. A heat transfer fluid flows in the tubes ( 3 ), the heat being transferred from the effluent in the duct through the molded coating, the upper surface of the poured material being in direct contact with the effluent flowing in the duct, but not with any inserted mechanical part.; The coating is composed of multiple layers having different material properties, i.e. a layer ( 9 ) of heat insulation material between the tubes ( 3 ) and the wall of the duct ( 2 ), a layer ( 10 ) of heat conducting material between the tubes and the effluent, in contact with the tubes, and an abrasion-resistant layer ( 11 ) on the surface, in contact with the effluent.

1 .- 15 . (canceled) 
     
     
         16 . A method for extracting heat from an effluent flowing in a duct, notably a main sewer, according to which a heat exchanger is installed at least in the bottom of the duct, which heat exchanger is immersed in the effluent, the heat exchanger is formed by coating of tubes with a sufficiently heat-conducting material poured around the tubes, and suitable for hardening in situ, the tubes being designed for the flow of a heat-transferring fluid, the exchange of heat with the effluent of the duct taking place through the molded coating, the top surface of the poured material coming into direct contact with the effluent flowing in the duct, wherein the coating is carried out in several layers of materials with different properties, namely:
 a layer of thermally insulating material between the tubes and the wall of the duct,   a layer of thermally conducting material in contact with the tubes, between the tubes and the effluent,   and, on the surface, in contact with the effluent, a layer of abrasion-resistant material.   
     
     
         17 . The method as claimed in  claim 16 , characterized in that, after having diverted or temporarily stopped the flow of effluent in the pipe, the exchanger is implemented directly inside the duct,
 by depositing, in the bottom of the duct, tubes for a circuit of heat-transferring fluid,   and by pouring in place the coating material in order to immerse the tubes therein, the material closely matching the profile of the bottom portion of the duct.   
     
     
         18 . The method as claimed in  claim 16 , wherein the coating material consists of at least one of the following materials: synthetic resin, thermally conductive cement or concrete, composite material optionally laden with thermally conductive additions or additives. 
     
     
         19 . The method as claimed in  claim 16 , wherein a protective film is inserted between the inner surface of the duct and the exchanger incorporated into this duct. 
     
     
         20 . The method as claimed in  claim 16 , characterized n that the tubes are placed parallel to the longitudinal direction of the duct. 
     
     
         21 . The method as claimed in  claim 20 , wherein the tubes, before pouring of the coating material, are kept parallel and spaced apart by a rack. Or a webbing fitted and bonded at the factory. 
     
     
         22 . The method as claimed in  claim 16 , wherein an intermediate webbing, made of metal or of synthetic fibers, is deployed before pouring of the coating material over at least a portion of a cluster of tubes in order to enhance the mechanical strength and/or improve the thermal transfer. 
     
     
         23 . The method as claimed in  claim 16 , wherein the tubes are flexible or semi-rigid in order to be able to be rolled up and unrolled continuously over a considerable length, notably of several tens of meters. 
     
     
         24 . The method as claimed in  claim 23 , wherein the tubes are made of flexible metal material or of synthetic material. 
     
     
         25 . The method as claimed in  claim 16 , wherein clusters of flexible tubes are prefabricated and that they are rolled up on reel-shaped supports for subsequent placement in the effluent duct by unrolling from the reel. 
     
     
         26 . The method as claimed in  claim 16 , wherein tubes for heat-transferring fluid are placed along the complete contour of the cross section of the duct, and that coating of the tubes is carried out over the whole contour of the section of the duct. 
     
     
         27 . The method as claimed in  claim 16 , wherein the internal surface of the molded material is horizontal. 
     
     
         28 . An exchanger for extracting heat from an effluent flowing in a duct, notably a main sewer, designed to be installed at least in the bottom of the duct and to be immersed in the effluent, the exchanger consisting of tubes embedded in a sufficiently heat-conducting material poured around the tubes that are intended for the flow of a heat-transferring fluid, the exchange of heat with the effluent of the duct taking place through the molded coating, to the exclusion of any fitted mechanical part, the upper surface of the poured material coming directly into contact with the effluent flowing in the duct, wherein the exchanger is produced according to a method as claimed in  claim 16 . 
     
     
         29 . An installation for extracting heat in an effluent duct, notably in a main sewer, wherein it comprises in the bottom, immersed in the effluent, at least one heat exchanger made according to the method of  claim 16 . 
     
     
         30 . The installation as claimed in  claim 29 , further comprising, in the areas of the internal wall of the duct that are situated above the effluent, pipes exposed to the atmosphere prevailing in the duct, through which pipes a heat-transferring fluid travels in order to recover a portion of the noticeable heat and of the latent heat from condensation of the water vapor.