The paper presents numerical analysis of heat recovery exchanger, which operates as an indirect evaporative air cooler in summer conditions and as a typical heat recovery unit during winter season. The numerical simulation is performed with the original mathematical model which is able to simulate the operation during summer and winter season. The model was validated against existing experimental data (operation as indirect evaporative air cooler) and against experimental data collected by authors at Wroclaw University of Technology (operation as heat recovery exchanger). Obtained results allowed for analysis of heat and mass transfer process occurring in considered exchanger during round-year operation. The characteristic heat and mass transfer zones for evaporative air cooler and heat recovery exchanger were established. Results also allowed for analysis of most important problems connected with achieving highest efficiency of the exchanger and achieving safe operating conditions during winter season (preventing the exchanger from freezing). Safe operating conditions (parameters of the ambient air in winter which would guarantee that no frost would be formed on the plates) were established. The analysis of the effectiveness of the novel exchanger with selected factors (i.e. obtained cooling capacity, thermal efficiency and relative effectiveness) was also presented in the paper. (C) 2015 Elsevier Ltd. All rights reserved.