This paper presents an innovative correlation associating the effectiveness (epsilon) of the cooling tower with its number of transfer unit (NTU) and vice versa. The new correlations can be used simply to predict the performance of wet counterflow cooling tower. Those correlations are based on solving heat and mass-transfer equation "enthalpy potential method" coupling with energy equations simultaneously. The validity of the correlations was checked by experimental data reported in the available literature. The results obtained from those new correlations showed a very good agreement with deviation less than 10% with those obtained from the literature for a temperature difference between the inlet water temperature and inlet air wet-bulb temperature (Tw(i) - Wbt(i)) equal to or less than 10 K. The main advantages of those correlations are: (1) its simplicity to be implemented through simple calculations of input parameters; (2) it provides helpful guidelines for optimization of cooling tower performance during its operation coupling with the thermal system at which the tower is connected. (C) 2014 Elsevier Ltd. All rights reserved.