Two-dimensional condensing vapor flow on parallel flat plates in an enclosure

Abstract

A vapor flow of pure fluid condensing onto a vertical flat plate in an enclosure was examined in order to develop knowledge of the mechanism of vapor condensation and flowfield characteristics. A specific Pyrex glass thermosyphon-like container filled with a certain amount of pure fluid, with or without noncondensable gas, was heated and the upward vapor flow between a pair of cooled parallel plates installed in the upper portion of the container was investigated by means of temperature and pressure sensors as well as laser holographic interferometry. With a pure fluid only (single-component, two-phase flow) in the container, the entire flowfield of condensation region is uniform in density and temperature. On the other hand, with a pure fluid containing a noncondensable gas (two-component, two-phase flow), a distinct flowfield structure is obtained. Its characteristics are: (1) the flowfield in the vapor/gas mixing region has a clear interfacial layer in the longitudinal or axial direction and a rather thick boundary layer near the cooled plate; (2) the condensing vapor flow has an oscillatory character with a low frequency of around 1 Hz, even in the steady-state flow and thermal conditions; and (3) sharp pressure drop was observed at the initiation of nonequilibriummore » vapor condensation when a large temperature difference existed between the vapor and the cooled plates. 12 references.« less