Recent interest in cooling towers, as a means of producing chilled water in conjunction with radiant
systems for cooling in buildings, has prompted interest in evaporative cooling in temperate maritime
climates. For such climates, evaporative cooling has the potential to offer an alternative approach to
refrigeration-based air-conditioning systems for producing chilled water, where conventional
refrigeration-based systems can, for certain buildings, be considered to be an over engineered solution
and where passive cooling is insufficient to offset cooling loads. The thermal efficiency of evaporative
cooling systems is a key performance indicator, as a measure of the degree to which the system has
succeeded in exploiting the cooling potential of the ambient air. The feasibility of this concept depends
largely however, on minimizing the approach water temperatures within an appropriate cooling tower,
at acceptable levels of energy performance. Previous experimental work for a full scale evaporative
cooling system has shown that it is possible to produce cooling water with low approach temperatures (1
e3 K), at the higher temperatures required in radiant and displacement cooling systems (14e18 C), with
varying levels of annual availability for different temperate climate locations. The current paper is
concerned with the development of a mathematical model which describes the behavior of such a low
temperature low approach direct evaporative cooling tower. The mathematical model is evaluated
against experimental data reported for a number of open tower configurations, subject to different water
temperature and ambient boundary conditions. It is shown that the discrepancies between the calculated
and experimental tower outlet temperatures are to within 0.29 C for a low temperature cooling water
process (14e18 C), subject to temperate climate ambient conditions and 0.57 C for a high temperature
cooling water process (24e30 C), subject to continental climate ambient conditions. Considering
the associated tower cooling loads, predicted results were found to be within a 6.93% root-mean-square
difference compared to experimental data. Furthermore, the influence of different cooling tower coefficients
on water outlet temperature and heat rejection of tower is investigated.