The role of the Merkel number is as

The role of the Merkel number is assessing cooling tower performance
has been examined by a number of researchers including:
Costelloe and Finn [7], Khan and Zubair [9], Bernier [10] and Kuehn
et al. [11]. Apart from the design of the cooling tower, the Merkel
number is strongly influenced by thewater to air (L/G) flow ratio, as
well as the inlet water temperature and the ambient air conditions
[7,10]. Using experimental data extracted from extensive testing of
the open cooling tower shown in Fig.1, Costelloe and Finn [7] report
that for a low temperature heat rejection tower (20e14 C), the
Merkel number is different than other correlations reported in the
literature, which were analysed at higher water rejection temperatures
(35e30 C) [10,11]. These differences reflect both the design
and operational issues associated with the low temperature, low
approach tower. Moreover, the Merkel number difference is most
marked at low L/G ratios, when a higher air flow rate is utilised.