Małgorzata Król

Numerical studies on the wind effects on natural smoke venting of atria

ABSTRACT Smoke management in the atrium with natural smoke venting is influenced by many parameters. These include the geometry of a building, external temperature and wind. The article presents the analyses of the impact of two wind speeds: 2.5 m/s and 7.5 m/s on conditions in the atrium. Volume flow rate of air inflowing to the atrium and the velocity of supply air in make-up air inlets were considered. The wind inflow from each direction was examined for two wind speed. This enabled the analyses of operation of particular make-up air inlets in variable external wind conditions. The possible impact of other buildings has been omitted. Moreover, the operation of exhaust openings was analysed. The subsequent step was examination of conditions in the atrium. The influence of wind, its speed and direction on soot mass fraction and its distribution in relation to the height of the atrium were considered. In addition, for some cases, visibility has been shown. It was proved that make-up air inlets located near the corner on the side wall parallel to the wind direction do not work properly, usually air flows through these openings to the outside. This allows to formulate guidelines for designers on the best locations of the inlet vents in buildings.

Optimization of a window frame by BEM and genetic algorithm

Genetic algorithms and boundary elements have been used to find an optimal design of a plastic window frame with air chambers and steel stiffeners. The objective function has been defined as minimum heat loss subject to a constraint of prescribed stiffness and weight of the steel insert.

Impact of the Factors Determining the Natural Stack Effect on the Safety Conditions in a Road Tunnel

Impact of weather conditions and natural stack effect on the operation of the mechanical ventilation system in a road tunnel is considered in the study. The work presents the measurements conducted in an opened road tunnel. Then, with the use of Ansys Fluent software the numerical model was built and validated. The numerical analyses were extended to other tunnel inclinations and temperature differences between tunnel portals. Taguchi method of experiment design was used to diminish the number of required simulations and to analyse the results.

Estimation of the Number of Threatened People in a Case of Fire in Road Tunnels

Factors influencing the conditions in a road tunnel in a case of fire were considered. The specifics of road tunnels as parts of the transportation network from the safety point of view was discussed. A brief overview on tunnel emergency systems and evacuation process was presented. Selected road tunnels in Poland were taken into account and a number of scenarios of traffic accidents with fire were detailed described. Some observations from carried-out full-scale hot smoke test were used. As a result of each such case study the estimated number of threatened tunnel users was obtained. Conclusion section contains some recommendations which would lead to increase the safety level in road tunnels.

The Choice of the Fire Ventilation System for a Short Road Tunnel

The operation of the natural ventilation system and the operation of the mechanical ventilation system with axial fans during the fire development were compared in the study. The study was founded on the numerical fluid mechanics. Two models were built corresponding to the two systems being tested. The use of the CFD program (Computational Fluid Dynamics) allowed for the comparison of the values of important parameters at any points of both tunnels. The temperature, the velocity of the air and hot gases and the soot concentration were examined. The results have shown that the operation of mechanical ventilation with the axial fans cleans the access road to the source of the fire from one of the portals. In the case of the natural ventilation the same, however worse evacuation conditions are maintained throughout the whole tunnel. But it should be remembered, that this type of ventilation system is very sensitive to the effects of ambient air parameters such as the temperature and the wind direction and speed.

Minimum Heat Losses Subjected to Stiffness Constraints: Window Frame Optimization

Genetic algorithm has been used to find an optimal design of the movable and fixed window framework taking into account their thermal interaction with the glass pane and the wall. The objective function has been defined as a minimum heat losses subjected to a constraint of constant stiffness and amount of steel. To accelerate the computations parallel processing has been implemented.