This paper numerically investigates the performance of the three highly efficient, advanced indirect evaporative air coolers: the "classical" cross-flow Maisotsenko cycle (M-Cycle) heat and mass exchangers and two novel combined M-Cycle air coolers proposed by authors. The novel heat and mass exchangers are based on a combination of parallel and counter-flow and cross and counter-flow schemes. An original mathematical models were developed and validated against experimental data. Analysis of the results allowed establishing appropriate operational parameters (i.e. airflow ratios and initial sections relative length) for the new heat exchangers. The novel units were compared with cross flow M-Cycle heat and mass exchanger. The main conclusion is that proposed solutions are characterized by higher cooling efficiency than the cross-flow M-Cycle unit. Combined cross-regenerative counter flow heat and mass exchanger obtained highest overall performance. (C) 2017 Elsevier Ltd. All rights reserved.