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Introduction. Chimney-type evaporative cooling towers, widely used at large thermal and atomic power
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plants for cooling circulating water [1 ], exert a substantial effect on their economic efficiency and ecological
situation in the neighborhood of the plants. The cooling of water in the tower depends on many factors, including
the aerodynamic conditions of the entry of cold air into the tower and the effect of wind loading and the mixing
of external air streams and warm water vapor in the lower part of the tower. We know of attempts to modify the
existing versions of the design of towers with the aim of improving the efficiency by aerodynamic means [2 ].
In order to gain a thorough understanding of the processes taking place in a tower and to carry out a
quantitative study of the main aerothermal processes, the present authors developed a laboratory model of the
chimney-type evaporative cooling tower. In this work we present the basic results of investigations obtained on the
laboratory setup devised. Preliminary results were published in [3 ].8514
In a cooling tower the interaction of warm water with cold air leads to the heating of a steam-air mixture
mainly due to the recondensation of vapor appearing as a result of the evaporation of the warm circulating water.
Inside the tower the Archimedes force generates a free convective flow of the warm vapor-air mixture containing
micron drops of water. The structure and intensity of this flow largely determine the efficiency of the processes of
evaporative cooling in such an installation. For large modern towers the height H and the diameter of the base D
are commensurable (H/D ~. 1); therefore the conditions for intake of air near the bottom and escape in the upper
part (with account for the wind speed) exert a substantial effect on the aerodynamic processes inside the tower. In
turn, the aerodynamic processes have a very marked influence on the processes of water evaporation.
As is known [4,5 ], to model free connective processes inside the cooling tower, in addition to the similarity
between the geometric dimensions of the model and the natural object there should be closeness of the physical
similarity numbers (Rayleigh, Ra, and Prandtl, Pr, numbers)
Ra = flgAT H3/vk,
(1)
Pr = v/k, (2)
where v is the coefficient of kinematic viscosity of a vapor-air mixture; k is the thermal diffusivity coefficient; g is
the free fall acceleration; fl is the temperature coefficient of volumetric expansion; AT is the temperature drop
between the heated air and the surrounding medium.