A general non-dimensional mathematical model of evaporative cooling devices
is applied to cooling towers. One of the benefits of the non-dimensional a
pproach is that the water-cooling efficiency of a cooling tower can be expr
essed as a function of only two variables and plotted in a single diagram f
or each type of cooling tower. For counterflow and parallel flow towers the
re is an analytic solution of the set of differential equations; crossflow
towers require a numerical solution. The resulting rating procedure of the
overall performance of a cooling tower is simple and consists of the adjust
ment of the assumed straight air saturation line to the real air saturation
data. All three types of cooling towers can be rated using the same proced
ure, if a diagram showing the water-cooling efficiency of the respective ty
pe is used. The accuracy of this method is checked by the use of published
data and is found to be good for the usual operating conditions, failing on
ly when the water-cooling range is very large. (C) Elsevier, Paris.