Abstract: The numerical simulation is used to study the influence of opening angle on the natural smoke exhaust ability for top and bottom hung windows. The smoke exhaust capacity of the top and bottom hung windows are evaluated by analyzing the mass flow, pressure and speed of the smoke outlet, and the main smoke exhaust area. The results show that the smoke exhaust efficiency of the bottom-hung window is obviously higher than the top-hung windows. Under the same o-pening angle and fire source power, the bottom-hung window c-an discharge 52% ~61% more smoke than the top-hung window. The relative mass flow of the top- hung window has an exponential relationship with the opening angle because the window structure is hindering the exhaust of smoke. When the opening angle is less than 64°, the main smoke exhaust area is the triangular area on both sides of the window, while the relative mass flow of the bottomhung window has little relationship with the open angle, and the window structure is beneficial to discharge smoke. When the opening angle is less than 56° , the main smoke exhaust area is the horizontal area near the lower side of the window, as the opening angle increases, the main smoke exhaust areas of the top and bottom hung windows transition to the vertical area under the far window. When choosing exhaust windows for buildings, it is recommended that bottom- hung window should be preferred, and the opening angle is 30° ; if top-hung window is selected, the opening angle should not be less than 60°. 

Key words:  , natural smoke exhaust, numerical simulation, tophung window, bottom-hung window