Vertical steam generator with a central downcomer

Claim 1

A VAPOR GENERATOR COMPRISING A VERTICAL ELONGATED CYLINDRICAL VESSEL ARRANGED TO OPERATE WITH AN UPPER VAPOR SPACE ABOVE A BODY OF LIQUID THEREIN; A VAPOR OUTLET FROM SAID VAPOR SPACE; PLATE MEANS COACTING WITH THE WALL OF SAID VESSEL TO FORM AN INTERIOR, VERTICALLY ELONGATED DOWNCOMER RESERVOIR AND AN ANNULARLY SHAPED VAPOR GENERATION CHAMBER EXTERIOR OF SAID RESERVOIR, SAID PLATE MEANS EXTENDING DOWNWARDLY TO SUBSTANTIALLY THE BOTTOM OF SAID VAPOR GENERATION CHAMBER BUT BEING SPACED THEREFROM TO ESTABLISH FLUID COMMUNICATION BETWEEN SAID DOWNCOMER RESERVOIR AND SAID VAPOR GENERATION CHAMBER; MEANS FOR SUPPLYING VAPORIZABLE LIQUID TO SAID DOWNCOMER RESERVOIR; AT LEAST THREE SEPARATE TUBE BUNDLES EACH COMPRISING A GROUP OF VERTICALLY ELONGATED U-TUBES ARRANGED IN ROWS LYING IN PARALLEL PLANES, SAID TUBE BUNDLES BEING LOCATED IN CIRCUMFERENTIALLY SPACED POSITIONS ABOUT SAID PLATE MEANS AND SUBSTANTIALLY FILLING SAID VAPOR GENERATION CHAMBER; AND HEATING FLUID INLET AND OUTLET MEANS COMMUNICATING WITH THE TUBES OF SAID TUBE BUNDLES FOR CIRCULATING HEATING FLUID THERETHROUGH.