Numerical Evaluation of the Effect of the Wettability of the Plates on the Performance of Indirect Evaporative Cooling Systems

Indirect Evaporative Cooling (IEC) systems exploit the latent heat of water vaporization to lower the temperature of an air stream, thus allowing to refrigerate an environment with reduced energy use compared to conventional air conditioning technologies. Several literature papers have shown that it is desirable that the plates of IEC recuperators are as uniformly wet as possible to promote water evaporation and improve the system performance. However, an accurate assessment of how plate wettability affects the effectiveness of IEC heat exchangers is difficult to obtain by means of experiments. As a consequence, in this study, a Computational Fluid Dynamics model, supported by experimental validation and which integrates a lumped parameter model to account for film evaporation, has been employed to estimate the potential impact of the plate wettability on the cooling performance of a cross-flow IEC heat exchanger. Specifically, a wide range of values of the wetting parameters was used as input for the numerical simulations, showing that a reduction of the plate contact angle, namely an increase in the wettability of the plates, improves the system effectiveness, as expected. However, for the analyzed recuperator, there is a flattening of the performance for plate contact angles lower than 50°, probably due to the intrinsic performance limitations of the cross-flow recuperator.