Condensation of steam on a vertical tube in a granulated material

Abstract

The heat transfer enhancement was studied during condensation of steam on a chilled vertical surface of a tube packed into a granulated material with different contact angles of wetting. The dimensionless values of heat transfer at condensation on a surface in filling, obtained for a vertical tube in the range of Reynolds numbers from 70 up to 400, exceed Nu* values for a smooth tube by the factor of 2–3. The intensification of heat transfer on a vertical tube, housed in a granulated layer, is conditioned by the several interdependent phenomena: 1 — capillary ascent of some liquid near the meniscuses, and as a consequence, reduction of the mean film thickness; 2 — burble of a film at the points of sphere contact with a surface of condensation at Re>10; 3 — removal of some film liquid by a granulated layer; accompanied by simultaneous film burble at the points of sphere contact with a cooling surface at Re>83.