Tubular heat exchanger, in particular receiving tube of a concentrating solar plant

Abstract

The present invention concerns a tubular heat exchanger ( 10 ) between a source of radiant heat located externally with respect to said tubular heat exchanger ( 10 ) and a heat-carrying fluid flowing inside the exchanger, the radiant heat coming from said source being concentrated on a longitudinal portion of the external surface of said tubular heat exchanger, comprising means ( 11 ) for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger.

1 . Tubular heat exchanger between a source of radiant heat located externally with respect to said tubular heat exchanger and a heat-carrying fluid flowing inside the exchanger, the radiant heat coming from said source being concentrated on a longitudinal portion of the external surface of said tubular heat exchanger, characterised in that it comprises means for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger. 
     
     
         2 . Tubular heat exchanger according to  claim 1 , characterised in that said means for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger comprise a plurality of protruding or recessive elements with respect to the internal surface of the tubular heat exchanger, positioned mainly in correspondence of said longitudinal portion of the external surface of the tubular heat exchanger on which the radiant heat coming from said source is concentrated. 
     
     
         3 . Tubular heat exchanger according to  claim 2 , characterised in that said protruding or recessive elements are positioned along the cylinder generatrixes of the tubular heat exchanger. 
     
     
         4 . Tubular heat exchanger according to  claim 2 , characterised in that said protruding or recessive elements are positioned along curves that do not follow the cylinder generatrixes of the tubular heat exchanger. 
     
     
         5 . Tubular heat exchanger according to any of  claims 2 - 4 , characterised in that the number and/or the surface of said protruding or recessive elements change in a circumferential and axial direction. 
     
     
         6 . Tubular heat exchanger according to any of  claims 2 - 5 , characterised in that the shape of said protruding or recessive elements change in a circumferential and axial direction. 
     
     
         7 . Tubular heat exchanger according to any of previous claims, characterised in that said means for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger comprise a thickness of the walls changing in a circumferential direction, between a minimum value in correspondence of said longitudinal portion of the external surface of the tubular heat exchanger on which the radiant heat coming from said source is concentrated, and a maximum value in correspondence of the longitudinal portion of the external surface of the tubular heat exchanger opposed to that on which the radiant heat coming from said source is concentrated. 
     
     
         8 . Use of a tubular heat exchanger as defined according to any of  claims 1 - 7  in a concentrating solar plant. 
     
     
         9 . Use of a tubular heat exchanger as defined according to any of  claims 1 - 7  in a hydrocarbon reforming plant for producing hydrogen or mixtures of methane and hydrogen or of hydrogen in presence of other hydrocarbons.