BT-28 Pressure Drop in Tubeside Falling Film Evaporators
To date, HTRI falling film evaporation studies have focused on heat transfer, so a conservative method was used for pressure drop calculations. We used the upflow boiling method which imparts a greater roughness effect to the film than gravity-controlled downflow actually has. To improve the current conservative approach, HTRI reviewed literature methods and data. Although existing usable data consist of the air-water system alone, several methods offer promising results and are discussed here in detail. The method we selected, modified for general use and to better fit existing data, provides an improved, much less conservative approach for use in future versions of Xist™. With additional data, the revised method can be tested more extensively.