<p>The Eulerian–Lagrangian approach is employed to simulate the complex humid air flow in single and double-inlet high-efficiency Stairmand cyclone separators. The humid flow is considered as the continuous phase, and the solid particles as the discrete phase. The unsteady simulation results indicate that the pressure drop decreases with an increase in inlet flow temperature for both dry and wet particulate flow. Moreover, an increase in relative humidity decreases the wet flow pressure drop. However, the difference between the pressure drops of double inlet cyclones is lower than that of a single inlet one. The pressure pattern of the single inlet cyclone is completely different from that observed in literature for dry air, in a way that the moisture content of the airflow at high temperatures leads to the instability in the flow vortex. While the vortex of the double-inlet cyclone straights directly towards the dust bin. Investigation of the effect of the convection coefficient shows that for both free and forced convection conditions, the velocity profile of the forced vortex remains constant, and an increase in the inlet temperature and convection coefficient only decreases the free vortex velocity. A detailed examination of the temperature field reveals that the low-temperature central part and high-temperature side wall of the vortex cause the re-entrainment of solid particles in clean flow by thermophoretic force. In conclusion, the double inlet cyclone is less sensitive to the inlet humidity ratio, considered the better choice for designers to operate with the incoming humid particulate flow compared to the single inlet one.</p>