Hydrodynamic operating regimes for a combined heat-and-mass exchanger

Abstract

Results are presented for hydrodynamic investigations of a model of a new design of vessel. Limits of the most effective operating regimes of the vessel are determined. A criterial equation is derived for determination of the height of the film layer -a quantity characterizing the operational effectiveness of the vessel on the whole.An original design of a combined heat-and-mass exchanger with two zones of phase contact, which is intended for the cleaning and cooling of gas, as well as condensation of viscous impurities contained in the gas, has been developed at the Moscow State University of Engineering Ecology.The combined vessel is shown in a schematic of an experimental plant (Fig. 1). The vessel housing is cylindrical. A flushing fluid is delivered into the upper part of the vessel, and distributed over its entire section, and gas is fed by counterflow into its lower section. Owing to characteristic design features of the vessel, a sufficiently large specific surface area of phase contact is ensured in the gas-liquid system.A flushing fluid delivered to a film sprayer creates a film that effectively separates the gas being delivered from the spray and particles of carbon black that exist in a mixture with resinous components of the liquid. This liquid is discharged under gravity through a lower connecting pipe. A gas is fed into the flushing liquid, which is accumulating in the lower portion of the vessel, and forms a foam layer.A literature search indicated the following. Golovachevskii [1] mentions a method for gas cleaning in which the gas is delivered using a Γ-shape branch pipe, and forms a foam layer in the lower section of the vessel, and a flushing fluid is atomized by nozzles in the upper section of the vessel. He also describes a vessel for heat-and-mass exchange and wet dust entrapment, which has two zones of phase contact -a foam layer, and a bed of a fluidized spherical packing on a perforated tray situated above. The construction of film sprayers is described in [2][3][4][5].Operating regimes and rules governing the operation of a film sprayer [5], and also the upper limit of the gas load, which corresponds to its effective operation as a separator, were determined as a result of analysis of literature sources.It is established that the maximum gas velocity in the tower should not exceed 0.9 m/sec, since when this condition is violated, a transitional operating regime sets in for the film sprayer, and it ceases to function as a separator.It must be noted that a new type of vessel with two stages of phase contact is a complex system, the high operating effectiveness of which is governed by combined processes in two zones of phase contact: a foam layer, and separating film.The mechanism responsible for cleaning of the gas consists of the following. The basic stage of this process takes place in the foam layer, and drops of liquid with contaminant particles settling on them are separated in the film, reducing splash-away and improving the effectiveness of the cleaning.The proposed design for the ...

The use of non-metal materials in the filler units of cooling towers with circulating water supply system

“…The fillers are the main structural elements of cooling tower that determine its cooling capacity. The filler is a contact device on the surface and in the volume of which the processes of heat, mass and momentum transfer take place [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”