冷却塔实验室模型英文文献和中文翻译(2)
In experiments we used a model of a cooling tower that had the same geometric proportions as in [6 ]. From
the viewpoint of physical criteria, there was similarity in the Prandtl number, since in both cases we used water
for the cooling. The Rayteigh number for the laboratory experiments lay within the range from 108 to 109. For
actual cooling towers 100 m in height Ra -~ 1015. Here the following should be noted: for Rayleigh numbers obtained
both in a laboratory installation and in an actual cooling tower, the flow inside the tower is turbulent in character.
This permits one to extend the results of laboratory modeling to actual objects.
Since under actual conditions cooling towers are exposed to the effect of wind loading, then in order to
simulate the interaction of an ascending free convective flow inside a tower with an external wind we introduce one
more similarity parameter
S = v/w, (3)
where v is the speed of the wind; w = X/2flgATH is the calculated vertical velocity of free convective flow. In
experiments the parameter S varied within the range from 0 to 2.
The problem of the selection of similarity numbers to simulate the processes of evaporative cooling in towers
is much more complex. In experimental investigations use was made of water and air as heat agents, as is done in
the majority of actual towers. Therefore, there was similarity in all of the thermophysical parameters. To take into
account the integral effect of thermodynamic and aerodynamic factors on the process of evaporative cooling of water,
we shall make use of certain results of [7 ].
It is shown in that work that the drop in the temperature of water in a tower ATw depends on the limiting
drop in the temperature of cooling ATIi m and on the relationship between the mean mass flow rates of water Qw
and air Qa through the cross section of the tower in the following way:
(Qw) (4) AT w=ATlim/ 1 +A~ ,
where ATw = TO-- Tf. Here Ty is the temperature of water in the tank, T O is the temperature of water entering the
water distributor; ATIi m = Tlim - T 0, where Tit m is the limiting cooling temperature [1 ] determined from the
condition
Ps (Zlim) = Ps (Za) ~, (5)
whereps(T) is the density of saturated vapors at the given temperature; ~p is the relative humidity of the surrounding
air.
The parameter A in Eq. (4) can be determined only experimentally. It is a slowly varying function that
depends on the character of water spraying, the design of the water-distributing system, and the elements in the
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