Case Study On Fire/Smoke Simulation in Basement Car-Parks
Fire safety in underground car parking is important, as accidental fires can be dangerous. When a fire breaks out in an underground car park, a large amount of smoke is generated at high temperature leading to poor visibility and difficulty in evacuation. In most cases, the victims are poisoned or starved of oxygen by the smoke. In addition, the smoke also causes most of the damage to the vehicles. In the event of a fire the first priority is to expel the smoke from the car parking and installed ventilation system should work efficiently, thereby enabling the quick and safe evacuation of people from the car park and also providing the smoke free area for fire fighters to control the fire.
Simulation of smoke propagation inside a car park basement involves modeling heat generation by fire, effects of buoyancy due to temperature, smoke species concentrations, velocity and pressure variations caused by mechanical ventilation system in operation. CFD analysis provides a detailed picture of the smoke path inside the basement with smoke concentration profiles at different times and different positions inside the building. This is difficult to obtain by experiments, because experiments can be time consuming, costly and sometimes fire and smoke related experiments inside the buildings can be dangerous as well.
In this work fire is modeled as combustion of gasoline fuel in the car fire with a total heat release rate of 4 MW with convective & radiation effects ( 4 MW is standard for a car-park with sprinkler system). In the fire simulation the first 10 minutes the fire continues with constant 4 MW of fire load and after that fire stops. The fire source is represented as a rectangular block of length 4 m, width 1.5 m and height 1.3 m situated in parking area. There is one fire source present in each individual zone of basement (zones which have water curtains or fire damping walls). During fire simulation, however, as per the client specifications, all the fans (Axial and Impulse Jet Fans) run at high/full speed configuration. All assumptions have been made according to client requirements & Industrial Standards.
The main objectives is to check the effectiveness of the ventilation system in case of fire, the smoke should be directed to exhaust, so that the fire can be put out and there should be clear visibility for the people to escape at stipulated time as per BS 7346-7; 2006.
The output of analysis is in the form of report containing velocity profiles, temperature and smoke layer profiles at different sections and levels. In addition, a compliance summary with the standards is also provided.