Method for extraction heat from an effluent, especially waste water, circulating in a conduit, heat exchanger and material for implementing said method

Abstract

The invention relates to a method for extracting heat from an effluent ( 2 ) circulating in a conduit ( 1 ), especially a waste water collector, according to which a heat exchanger (E) is installed, at least in the bottom of the conduit, said heat exchanger (E) lying in the effluent and being formed by coating tubes ( 3 ) with sufficiently heat-conductive concrete cast around the tubes intended for the circulation of a heat-transfer fluid, the heat exchange with the effluent of the conduit being carried out through the moulded coating. The concrete ( 4 ) of the coating consists of a least 50 weigh % of silicon carbide, a load of needles made of a heat-conductive and mechanically resistant material, a binding agent and the remainder of alumina, metal powder or carbon.

1 . A method for extracting heat from an effluent flowing along a pipe, notably a sewer, the method comprising installing, at least in the bottom of the pipe, a heat exchanger (E) which is immersed in the effluent the heat exchanger (E) being formed by coating tubes with a sufficiently thermally conductive concrete poured around tubes through which a heat-transfer fluid is intended to circulate, the exchange of heat with the effluent of the pipe taking place through the cast coating,
 wherein the coating concrete is made up of at least 50% by weight of silicon carbides of an acicular filler of needles of a thermally conductive and mechanically strong material, of a binder and the rest being alumina, metallic powder or carbon.   
     
     
         2 . The method as claimed in  claim 1 , wherein the acicular filler of needles represents more than 2% by weight. 
     
     
         3 . The method as claimed in  claim 1 , wherein, the needles of the acicular filler are made of metal, particularly of carbon steel or of aluminum, or are made of carbon. 
     
     
         4 . The method as claimed in  claim 1 , wherein the diameter of the needles is less than five-tenths of a millimeter for a length generally of less than 10 mm. 
     
     
         5 . The method as claimed in  claim 1 , wherein the needles are ferritic needles. 
     
     
         6 . The method as claimed in  claim 1 , wherein:
 a layer of thermally insulating material is placed between the tubes and a wall of the pipe,   a layer of conductive concrete is placed in contact with the tubes, between the tubes and the effluent,   and, at the surface, a layer of abrasion-resistant material is placed in contact with the effluent.   
     
     
         7 . The method as claimed in  claim 1 , wherein an intermediate mesh made of metal or synthetic fibers is spread over the tubes, prior to the pouring of the coating material, over the entire extent of a portion of the exchanger so as to enhance mechanical strength and/or improve heat transfer. 
     
     
         8 . The method as claimed in  claim 1 , wherein the tubes are ringed. 
     
     
         9 . The method as claimed in  claim 1 , wherein the tubes are made of plastic. 
     
     
         10 . The method as claimed in  claim 1  wherein the tubes are flexible. 
     
     
         11 . An exchanger for extracting heat from an effluent flowing along a pipe, notably a sewer, installed at least in the bottom of the pipe so that it is immersed in the effluent, the exchanger comprising tubes embedded in a thermally conductive concrete poured around tubes through which a heat-transfer fluid is intended to circulate, the exchange of heat with the effluent of the pipe taking place through the cast coating,
 wherein the coating concrete is made up of at least 50% by weight of silicon carbide, of an acicular filler of needles of a thermally conductive and mechanically strong material, of a binder, the rest being alumina, metallic powder or carbon.   
     
     
         12 . The exchanger as claimed in  claim 11 , wherein the tubes embedded in the concrete are ringed tubes. 
     
     
         13 . The exchanger as claimed in  claim 11 , wherein the ringed tubes are made of plastic. 
     
     
         14 . The exchanger as claimed in any one of  claim 11 , wherein the tubes are flexible. 
     
     
         15 . A material for implementing a method as claimed in  claim 1 , the material comprising a mixture made up of at least 50% by weight of silicon carbide, of an acicular filler of needles of a thermally conductive and mechanically strong material, of a binder, the rest being alumina, metallic powder or carbon. 
     
     
         16 . The material as claimed in  claim 15 , wherein the acicular filler of needles represents at least 2% by weight. 
     
     
         17 . The material as claimed in  claim 15 , wherein and the acicular filler of needles are made of metal, particularly of carbon steel or of aluminum, or are made of carbon.