In order to evaluate the thermal performance of the IEC by simplified methodology with reasonable accuracy and certainly with less computational time, lumped solution is considered the easiest approach to do that [1,2]. In modeling simultaneous heat and mass transfer process, it introduces complexities in the heat and mass transfer calculations. Goodman [11] developed and presented the potential enthalpy approach to solve the simultaneous heat and mass transfer problem. Threlkeld [12] detailed the enthalpy potential method and presented the logarithmic mean enthalpy difference (LMED), which is analogous to logarithmic mean temperature difference for dry heat exchanger. However, the enthalpy difference is the driving force in wet cooling towers. This method (LMED) has been adopted by many authors such as Facao and Oliveira [13,14]. The second method to simulate the wet heat exchanger is the ε-NTU. One of the benefits with the ε-NTU method for dry heat exchanger is that it can be solved explicitly without iteration. Only the inlet conditions are needed to solve for the heat transfer rate. Alternatively, ε-NTU method for wet heat exchanger is, unfortunately, still an iterative process. Braun et al. [15] developed “effectiveness models” for cooling coils and cooling towers, which utilized the assumption of a linearized air saturation enthalpy and the modified definition of NTUs. The models were useful for both design and system simulation. However, Braun’s model needs iterative computation to obtain the output results and is not suitable for online optimization [16]. Stabat and Marchio [17] adapted the traditional ε-NTU for dry heat exchanger to develop a simplified model for the ICT. The simplification of their model was constructed on the simplification of energy balance and heat and mass transfer equations. The model was solved on iterative approach by assuming the output conditions of the ICT. Hasan [18] modified the traditional ε-NTU for counter/parallel sensible heat exchanger by implementing new mass flow rate parameter. There is no need for the iterative process to use the ε-NTU correlation for wet heat exchanger. The wet specific heat, which represents the iterative term of the wet ε-NTU correlation, has been replaced by the slope of saturation line. Recently, Kim et al. [19] presented an empirical equation, which correlates the effectiveness of wet/dry heat exchanger with the major design parameters through a linear regression equation. The developed correlation was proposed on 2^{k}-factorial experiment design method to estimate the impact of the design parameters and their interactions on the effectiveness of a wet IEC. The superscript *k* reflects the number of parameters considered in the experiments. Most of those simplified models were developed based on assuming Lewis number of a unit value. Xia and Jacobi [20] declared that the assumption of unity value of Lewis number causes the major source of error in LMED method and a difference of 8% could be introduced in evaluating the total heat transfer rate, under the operating condition of a sensible heat ratio of 50%, as the value of Lewis Factor changed from 1 to 1.16. Recently, Xia et al. [21] suggested that the relative calculation error for the total heat transfer rate could be as high as 20% as a result of assuming Lewis number of unit value.