HEAT-TRANSFER IN A FALLING FILM ON A HORI ZONTAL TUBE

As the initial flow of a falling film above one or several horizontal tube is known, we propose a model which permits the determination of t he local heat transfer coefficient. The model is valid for Reynolds nu mbers lower than 2000 and for either a constant flux or a constant tem perature. The fraction of the film which is evaporated after its passa ge over the exchange surface is taken into account. The calculated exc hange coefficients, the film thickness and the Nusselt numbers are com pared with the numerical and experimental results of different authors . The agreement is good, particularly for the case of estimation of th e average Nusselt number for Reynolds numbers greater than 1000.