<p>The present study investigates the effect of the airflow humidity and temperature on its irreversibility at single and double-inlet cyclone separators. The entropy generation theory is employed to determine the contribution of the thermal, frictional, and turbulent dissipations to total exergy loss. Moreover, the effect of the heat transfer mode (e.g., free and forced convection) at different free stream velocities on total irreversibility is examined. The results show that turbulent dissipation is the main mechanism that dissipates the vortex flow exergy. Moreover, the dry air vortex has the highest irreversibility, and it decreases with an increase in the relative humidity ratio. A comparison between the inlet velocities of 11.99 m/s and 16.04 m/s shows that the corresponding entropy generation increases by about 140% in the moisture-free air. However, at the humidity ratios of 20% and 40%, this value increases up to 185.6% and 214.2%, respectively. Using the double inlet type reduces the total entropy generation compared to the single inlet one. However, as the inlet flow moisture increases, their difference becomes lower. Moreover, it is found that the irreversibility of the double inlet type is more sensitive to the dust bin backward flow, especially at higher temperatures. The interesting point is that the total entropy generation of the double inlet cyclone is lower than the single inlet type by about 10%, while their pressure drop is approximately in the same range. In addition, an increase in the convection coefficient has no significant effect on total exergy loss.</p>