The Effects of Wind on the Compartment Fire with Cross Ventilation - Research Paper Example

The rate of burning is a significant variable that acts as an indicator of the coupling between thermal and oxygen vitiation effects (Bishop & Drysdale, 1995). In cases where small-scale studies are involved the radiation attenuation of the flame has been found to be small leading to a situation where the influence of compartment radiation feedback on the rate of evaporation is stronger in comparison to that at a large scale (Ringwelski, 2001; Rangwala, 2002). The large increases experienced in the burning rate over the free burn values need to be given an interpretation of a scale effect.

This paper is an experimental investigation to determine the wind effects on compartment fire with cross ventilation. This acts as the initial step in understanding the means through which measures necessary for fire safety building under wind should be undertaken. In this experimental setup, fire inset to burn under steady airflow from a wind boundary. This is a simulation of a fire compartment set to be on a higher/tall building, which is an explanation of the effect of wind on fire under cross ventilation.

Buildings with cross ventilation have a considerable height of about 3-4m high within the rooms per floor. Therefore, wind speed variation is not a necessary factor to consider in high-rise buildings. Thus, the major consideration in these buildings is a wind attack on the building. Since the building acts as a barrier to wind, it acts as a blockage to the wind. Moreover, it is necessary to consider the effect of a steady flow of air in a wind boundary. However, a profile of the wind speed at different levels of the building height is a major determinant of the wind effect on the fire in cross ventilation (Naveen and Kumar, 2007).1.2Need for the StudyThis research is much needed to prove the abilities of Fire Dynamic Simulator (FDS) in order to predict the behaviour of compartment fire in various ventilation conditions.

Apart from validating FDS, this study is very significant as wind effect on compartment fire in cross-ventilation condition has not been fully studied (Kumar & Naveen, 2007; Haxiang Chen, et al., 2009; Feasey and Buchanan, 2002).

3 Research Aims and Objectives The main concern of the research was to determine impact of wind on across ventilations and Fire Behaviour. In order to carry out the study in appropriate directions, identification of the clear and comprehensive research objectives is needed. Therefore, following some of the research objectives are identified that aim to find out effect of wind on fire in across ventilation 1. To determine to what extent the speed of wind affect the production and dispersion of smoke thus affect visibility 2.

To find out the effect of wind in across ventilation on heat release in compartments and the FDS simulations. 3. To carry out simple simulations on the behaviour of fire cross ventilation with wind effect 4. Design different scenarios and trends of wind condition by the use of FDS. 5. To validate the FDS field model. 1.4 Research questions In this paper, the questions that needs to be answered are Does heat release rate differ at different velocities of win in across ventilation? How does smoke move within a room under different wind velocities?

In the study, FDS will be used to help measure visibility and heat release rate. In a standard FDS model smoke deposit will lead to decreased optical density due to a formed layer of soot. This will lead to optimistic detection of visibility in the model. This will give a result that is reliable. FDS model helps in modelling the spread of smoke in a compartment thus helping to know the size of ventilations to be provided in designing a compartment. It also helps in modelling where all indicators of fires and smoke are considered which other models do not consider.

The model is accurate and considers various fire scenarios. The model considers time as conditions of fire changes. It uses fluid flow technique which puts emphasis on the flow of gases because they have turbulence. 1.5. Research methodology The study will use FDS to obtain fire simulation visibility, Heat release rate and temperature in three different velocities of wind on across ventilations. Then thermocouples will be used to measure smoke and temperature. It also explains the need of validation of FDS in order to carry out the current research and the use of the outputs of the Kumar’s Experiment in order to validate the FDS to carry out the main experiment in the area intended to be explored by the author. 1.6 Main Achievement of the Research Objectives As the considered study is qualitative in nature; therefore, the development of the research objectives was done accordingly.

The objectives were: To identify the Relative visibility of exit sign for across ventilations at different wind conditions and the critical times taken for visibility to be obscured. To determine the impact of wind conditions on heat release rates in compartments with across ventilation and the FDS simulations.. To find out the effect of wind conditions on Fire safety in the building. The study results and analysing showed the impact of ventilation to a smoke layer descending and heat release rate.

It showed that wind velocities reduce visibility in the presence of soot and temperature. 1.7. Summary There are three research objectives are identified that collectively follow a sole aim of to predict the smoke properties inside a compartment under different wind conditions. Comparisons were done on the simulation results from the three different wind conditions. The simulated temperature from the FDS shows good results which is comparable with the experiment. The movement of smoke within the compartment were well measured and simulated which had small deviations from expectation.

The result of wind with speed of 3m/s and 5m/s showed almost similar results at one point however where the speed of wind was 0m/s had poor visibility. This results were monitored using cameras and by optical instruments to view light extinction and smoke production. The results confirmed that wind conditions are responsible for smoke production and dispersion, and heat release rate depends on the air provided thus influence of wind. 1.