Heat exchanger for molten salt steam generator in concentrated solar power plant

Abstract

A hairpin heat exchanger (1), wherein the bundle of parallel U-bent tubes (2) is extended out of the exchanger and connected, via bent tubes (11), respectively beyond an end of the internal shell (3) and of the external shell (4) at the first straight section to a first header (9) distributing the first fluid to the bundle of straight tubes (2) and beyond an end of the internal shell (3) and of the external shell (4) at the second straight section to a second header (10) collecting the first fluid under the form of liquid, vapor or a mixture liquid/vapor from the bundle of straight tubes (2).

1 . A hairpin heat exchanger, comprising:
 a first straight section;   a second straight section; and   a bent section linking the first straight section and the second straight section,   wherein each straight section comprises a part of a first cylindrical shell or internal cylindrical shell and of a second cylindrical shell or external cylindrical shell, the first cylindrical shell being located inside the second cylindrical shell, both forming an intershell space enclosing a bundle of parallel U-bent tubes having each a first and a second straight part respectively located in the first and second straight section of the exchanger and a 180°-bent part located in the bent section of the exchanger,   wherein, in use, a first fluid to be heated and vaporized is flowing, the external cylindrical shell comprising respectively at one end an inlet and at another end an outlet for a second fluid comprising a hot thermal fluid, so that, in use, the second fluid flows in the intershell space and cools down by exchanging heat with the first fluid flowing in the straight tubes, the intershell space enclosing baffles to guide the second fluid, and   wherein the bundle of parallel U-bent tubes is extended out of the exchanger and connected, via bent tubes, respectively beyond an end of the internal shell and of the external shell at the first straight section to a first header configured to distribute the first fluid to the bundle of straight tubes and beyond an end of the internal shell and of the external shell at the second straight section to a second header configured to collect the first fluid, comprising liquid, vapor, or a mixture liquid-/vapor, from the bundle of straight tubes.   
     
     
         2 . The hairpin heat exchanger according to  claim 1 , wherein the exchanger is horizontal, and
 wherein in which a flow of the second fluid with respect to a flow of the first fluid is either co-current or counter-current.   
     
     
         3 . The hairpin heat exchanger according to  claim 1 , wherein the first header and the second header are straight and cylindrical, or spherical. 
     
     
         4 . The hairpin heat exchanger according to  claim 1 , wherein the first fluid comprises a fluid comprising feedwater or supercritical carbon dioxide. 
     
     
         5 . The hairpin heat exchanger according to  claim 1 , wherein the second fluid comprises a molten salt or a mixture of molten salts, a thermal oil, or liquid sodium. 
     
     
         6 . The hairpin heat exchanger according to  claim 1 , wherein the baffles comprise continuous helical baffles. 
     
     
         7 . The hairpin heat exchanger according to  claim 1 , e wherein the baffles are assembled to the internal cylindrical shell. 
     
     
         8 . The hairpin heat exchanger according to  claim 1 , further comprising a tube sheet between the first header, the second header respectively, and a hairpin section of the exchanger containing the internal and external cylindrical shells. 
     
     
         9 . The hairpin heat exchanger according to  claim 8 , wherein the tube sheet has elliptical shape and comprises passageways configured to allow sealed passage of the U-bent tubes through the tube sheet. 
     
     
         10 . (canceled) 
     
     
         11 . The hairpin heat exchanger according to  claim 1 , further comprising a sealing device between the external shell and the baffles. 
     
     
         12 . The hairpin heat exchanger according to  claim 1 , further comprising a distribution jacket configured to uniformly feed the second fluid from the thermal fluid inlet to the heat exchanger. 
     
     
         13 . The hairpin heat exchanger according to  claim 12 , wherein the distribution jacket comprises a plurality of openings distributed at 360° over an internal face thereof. 
     
     
         14 . The heat exchanger according to  claim 1 , wherein the heat exchanger provides an evaporator function. 
     
     
         15 . The heat exchanger according to  claim 1 , wherein the heat exchanger provides a superheater function. 
     
     
         16 . The heat exchanger according to  claim 1 , wherein the heat exchanger provides a reheater or an economizer function. 
     
     
         17 . The heat exchanger according to  claim 1 , wherein the heat exchanger provides an evaporator, superheater, reheater or economizer function so as to provide at least one heat exchanger train in a molten salt steam generator (MMSG). 
     
     
         18 . The heater exchanger according to  claim 17 , wherein the superheater, the reheater, and/or the economizer are configured to run counter-current, while the evaporator is configured to run co-current. 
     
     
         19 . The method according to  claim 17 , wherein the molten salt steam generator comprises a once-through or a forced circulation steam generator. 
     
     
         20 . The hairpin heat exchanger according to  claim 7 , wherein the baffles are welded or bolted to the internal cylindrical shell. 
     
     
         21 . The hairpin heat exchanger according to  claim 13 , wherein the plurality of openings are configured to feed the second fluid into a first turn of the helical baffle.