Tubulous vapour generator

Claim 1

A FORCED FLOW ONE-THROUGH TUBULOUS VAPOR GENERATOR INCLUDING MEANS FORMING A GAS FLOW PATH, MEANS SUPPLYING HEATING GASES TO SAID GAS FLOW PATH, INLET HEADER MEANS, OUTLET HEADER MEANS, MEANS SUPPPLYING VAPORIZABLE FLUID TO THE INLET HEADER MEANS, MEANS FORMING A VAPOR GENERATING SECTION DISPOSED IN SAID GAS FLOW PATH AND COMPRISING FIRST AND SECOND SECTIONS ARRANGED IN PARALLEL FLOW RELATION AND EXTENDING BETWEEN SAID CONNECTED TO SAID INLET AND OUTLET HEADER MEANS SO THAT THE FLUID PRESSURE DROP BETWEEN THE INLET AND DISCHARGE SIDES OF THE FIRST SECTION IS SUBSTANTAILLY THE SAME AS THE FLUID PRESSURE DROP BETWEEN THE INLET AND DISCHARGE SIDES OF THE SECOND SECTION, THE FIRST SECTION HAVING A SUBSTANTIALLY GREATER AMOUNT OF HEAT EXCHANGE SURFACE THAN THE SECOND SECTION AND DISPOSED UPSTREAM IN THE GAS FLOW PATH OF THE SECOND SECTION, FLOW RESISTANCE MEANS EFFECTING A FLUID PRESSURE DROP IN THE INLET PORTION OF THE SECOND SECTION SUCH THAT THE REGION OF THE SECOND SECTION IN WHICH EVAPORATION COMMENCES IS DISPOSED DOWNSTREAM IN THE HEATING GAS FLOW PATH OF THE REGION OF THE FIRST SECTION IN WHICH EVAPORATION COMMENCES AND PROVIDING A SUBSTANTIALLY LOWER OPERATING PRESSURE IN THE SAID REGION OF THE SECOND SECTION THAN IN THE SAID REGION OF THE FIRST SECTION.