T. Niederhauser et C. Trepp, HEAT AND MASS-TRANSFER IN WATER AMMONIA F ALLING FILMS AT SMOOTH AND ROUGH TUBES, Warme- und Stoffubertragung, 29(4), 1994, pp. 251-264
The present paper studies the water/ammonia film falling down along ev
aporation tubes. Heat and mass transfer coefficients with smooth, sand
blasted, knurled and spine tubes were measured and compared to values
found in literature. The experiments cover the laminar-wavy flow range
and the concentration range between 45 and 70 weight percent of ammon
ia. Compared to other working mixture pairs the mass transfer with smo
oth tubes is clearly higher in the water/ammonia film. The heat transf
er, however, does not vary substantially compared to the values of the
other liquid mixtures. Knurling the wall improves primarily the heat
exchange. But only a direct disturbance of the gaseous-liquid interpha
se did result in a considerably accelerated mass transfer through the
film.