Falling-Film Evaporation on Tube Bundle with Plain and Enhanced Tubes—Part II: New Prediction Methods

Abstract Many parameters influence the falling-film evaporation process and, despite numerous studies, the basic mechanisms remain only partially clear, making the prediction of heat transfer still mainly an empirical process. The most important thermal design parameters that need to be predicted are the onset of dryout of the falling evaporating film, which signals a severe degradation in the evaporator performance and the local heat transfer coefficients for all-wet and partially dry conditions. Based on the experimental results in the previous article is this issue, Part I [1], a new, quite general method for prediction of the onset of dryout on plain and enhanced tubes has been developed. For heat transfer, a general format for predicting local performance on a single row and on a tube bundle is proposed, but the method still requires fluid/tube specific empirical constants to be implemented. Nevertheless, these methods represent significant improvements in the thermal design methods available for falling-film evaporators.