Vapor generating unit

Claim 1

A VAPOR GENERATING UNIT COMPRISING WALLS FORMING A VERTICALLY ELONGATED PRESSURE VESSEL OF CIRCULAR CROSSSECTION ARRANGED TO OPERATE WITH A LIQUID LEVEL SEPARATING AN UPPER VAPOR SPACE AND A LOWER LIQUID SPACE, A VAPOR OUTLET FROM SAID VAPOR SPACE, PLATE MEANS COACTING WITH SAID PRESSURE VESSEL WALLS AND FORMING A VERTICALLY ELONGATED VAPOR GENERATING CHAMBER AND A DOWNCOMER PASSAGE WITHIN THE LIQUID SPACE OF SAID VESSEL, SAID PLATE MEANS EXTENDING DOWNWARDLY TOWARD AND BEING CLOSELY SPACED ABOVE THE BOTTOM OF SAID VAPOR GENERATING CHAMBER AND ARRANGED WITH RESPECT TO THE PRESSURE VESSEL WALLS SO THAT THE VAPOR GENERATING CHAMBER FILLS A GREATLY PREDOMINATING PART OF THE LOWER PORTION OF SAID VESSEL, A VAPOR-LIQUID MIXTURE OUTLET LOCATED IN THE UPPERMOST PORTION OF SAID VAPOR GENERATING CHAMBER, VAPOR-LIQUID SEPARATING MEANS POSITIONED ABOVE SAID VAPOR GENERATING CHAMBER AND ARRANGED TO RECEIVE THE VAPOR-LIQUID MIXTURE FROM SAID OUTLET WHILE DISCHARGING SEPARATED LIQUID DIRECTLY TO SAID LIQUID SPACE AND SEPARATED VAPOR DIRECTLY TO SAID VAPOR SPACE, SAID VAPOR-LIQUID SEPARATING MEANS ARRANGED WITH RESPECT TO SAID PLATE MEANS TO MAINTAIN SAID LIQUID LEVEL ABOVE SAID VAPOR GENERATING CHAMBER AND IN DIRECT COMMUNICATION WITH SAID DOWNCOMER PASSAGE, SAID VAPOR GENERATING CHAMBER, VAPOR-LIQUID SEPARATING MEANS, LIQUID SPACE AND SAID DOWNCOMER PASSAGE BEING SERIALLY CONNECTED AND FORMING A DISTINCT VAPORIZABLE FLUID CIRCULATION FLOW CIRCUIT WITHIN SAID VESSEL, A PLURALITY OF TUBES CONSTITUTING A VERTICALLY ELONGATED BUNDLE ARRANGED TO SUBSTANTIALLY FILL SAID VAPOR GENERATING CHAMBER, AND MEANS FOR PASSING A HEATING FLUID THROUGH THE TUBES OF SAID BUNDLE.