Way back in 2013, I decided to write an article to delineate quantum leaps in steam locomotive technology that would have evolved (I assume) if steam were still in use. First on the list was a new style of superheater as the typical Schmidt style was grossly inefficient. In about 1/3 of the superheater tube, the steam temperature inside the tube was hotter than the combustion gasses in the flue. As heat ALWAYS moves from hotter to colder, superheated steam was being cooled in the smokebox end of the flue.

The first practical firetube superheater was patented in 1912. The intended application was in steam locomotive boilers. Tests proved that thermodynamic efficiency could be improved up to 30%. Fuel consumption could be reduced 30% for the same load, or 30% more tons of freight could be pulled for the same fuel. There was an impediment to its success. In the existing technology of the era, welding was not viable. The return bends were threaded cast steel that were not reliable in rigorous locomotive service. In 1916, a forging process was patented whereby a single return bend was forged from two tubes. This supplied the reliability required. By 1919, three thousand locomotives a year were being manufactured and most locomotives built since 1900 were being retro-fitted with superheaters. Steam was superheated in a firetube boiler by adding larger size firetubes in the tube bundle and populating these "superheater flues" with small diameter tubing elements where the steam flows from the low gas temperature exit end of the firetube toward the high gas temperature furnace end of the firetube. The superheater element tubing has a 180 degree return bend that reverses the flow to send the now superheated steam out of the boiler. Because the traditional firetube superheater requires 2 tubing elements occupying a larger diameter firetube, there are inherent inefficiencies in the heat transfer. Temperature profile is derived using the methods derived by Lawford Fry.



The solution is to create an annular superheater tube with 100% efficiency. Heat flow is ALWAYS from hotter to cooler. From 1900 to the 1920s many patents were granted for annular superheaters, however, none were successful in implementation.





After successfully solving the mathematical and manufacturing issues, and happy with the results, I was cogitating on the implementations. One afternoon, I called up a buddy who was the Hawaii commercial laundry guru and presented, "if I could put a superheater in a laundry boiler and get 650F steam (vs. 350F) to put in a flatwork ironer and save 12% on the fuel, what are the implications? He said the fuel was irrelevant as the superheated steam would allow them to crank up the conveyor speed by 30% and finish an 8 hour shift in 5 to 6 hours.
Research indicated about 40,000 firetube laundry boilers in the USA and only about 2 dozen locomotives that would, could utilize my new design, I decided to aim for the real world market.
Twelve years later, 4 patents and several prototypes, it is time to launch.







More details at AA Superheater Co., Inc.