Thermal isolation screen for isolating an electromagnetic inductor, and heat treatment installation comprising such a screen

Abstract

Thermal insulation screen transparent to magnetic flux, intended to isolate an electromagnetic inductor with a transverse or pseudo-transverse field, from the radiation of a heated product ( 1 ), the thermal screen being made up of a matrix of blocks ( 7 ) made of a thermally insulating material and of a plurality of tubes ( 8 ) cooled by the circulation of a fluid, these tubes being imprisoned in said matrix of blocks and the tubes and the blocks being held in place by a support. The screen includes, behind the blocks, heat-conducting means ( 10 ) placed so as to intercept the heat flux passing through the blocks, these conducting means being thermally coupled to the cooled tubes ( 8 ) for discharging the heat flux into the tubes.

1 . Thermal insulation screen transparent to magnetic flux, intended to isolate an electromagnetic inductor with a transverse or pseudo-transverse field from the radiation of a heated product, the thermal screen being made up of a matrix of blocks made of a thermally insulating material and of a plurality of tubes cooled by the circulation of a fluid, these tubes being imprisoned in said matrix of blocks, the tubes and the blocks being held in place by a support, characterized in that it includes, behind the blocks, heat-conducting means placed so as to intercept the heat flux passing through the blocks, these conducting means being thermally coupled to the cooled tubes for discharging the heat flux into the tubes. 
     
     
         2 . Thermal insulation screen according to  claim 1 , wherein the heat-conducting means are equipped with means for preventing, or reducing, the formation of currents induced by the magnetic flux. 
     
     
         3 . Thermal insulation screen according to  claim 1 , wherein the heat-conducting means are formed by a metal screen thermally coupled to the cooled tubes. 
     
     
         4 . Thermal insulation screen according to  claim 3 , wherein the metal screen is formed by metal fins that extend to the rear of the blocks, each fin being in thermal contact with a cooled tube. 
     
     
         5 . Thermal insulation screen according to  claim 4 , wherein the fins are produced by lengths of metal wire that are fixed to the cooling tubes. 
     
     
         6 . Thermal insulation screen according to  claim 1 , wherein the means for preventing, or reducing, the formation of induced currents generated by the magnetic flux comprise slots made in the conducting means. 
     
     
         7 . Thermal insulation screen according to  claim 6 , wherein the slots are oriented transversely to the longitudinal direction of the tubes. 
     
     
         8 . Thermal insulation screen according to the  claim 4 , wherein the slots open onto the longitudinal edges of the metal screen and are closed near the central portion. 
     
     
         9 . Thermal insulation screen according to  claim 4 , wherein each fin extends on either side of a tube. 
     
     
         10 . Thermal insulation screen according to  claim 9 , wherein each fin extends, on each side of a tube, over substantially half the gap between two adjacent tubes. 
     
     
         11 . Thermal insulation screen according to  claim 4 , wherein each fin is welded to a tube. 
     
     
         12 . Thermal insulation screen according to  claim 4 , wherein the fins are formed by slots made in an extruded or drawn metal screen/tube assembly made as a single part. 
     
     
         13 . Thermal insulation screen according to  claim 4 , wherein the region of the fin adjacent to the tube has the form of a cradle that follows a portion of the contour of the tube. 
     
     
         14 . Thermal insulation screen according to  claim 4 , wherein the fins are provided over the entire length of the tubes, in the region of the inductor to be protected from the heat flux. 
     
     
         15 . Heat treatment installation, especially a furnace, which includes an electromagnetic inductor having a transverse or pseudo-transverse field, for heating a product, characterized in that it includes, for protecting the inductor against the thermal radiation of the heated product, at least one thermal screen according to  claim 1 .