The Effect of Swirl Flow upon the Performance of Monotube Steam Generators

Steam heat transfer and pressure loss correlations and a thermal design procedure are presented which permit automotive steam generators to be designed on a local basis both with and without swirl generating boiler tube inserts. Example designs with and without inserts are analyzed for a boiler producing steam at 1500 psia and 1100F. The results obtained show the boiler tube with insert would operate approximately 100F cooler than a tube without insert or alternatively, the tube without insert would be 50% longer for the same wall temperature. Limited parametric calculations indicate that an advantageous boiler arrangement is one in which the evaporating region is located near the hottest combustion gases with the superheater region near colder combustion gases. This arrangement would result in boiler tube wall temperatures approximately 100F cooler than a counterflow arrangement.