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CFD Modelling Study of Mechanical Ventilation System in Basement Car Park under Emergency Mode

C2D Solutions Pte LtdConcepts To Design Solutions

Problem Statement

The main purpose of a ductless mechanical ventilation systems for a car park in a fire situation is to achieve acceptable level of fire safetyrequirements within the enclosure.

ChallengeIt is assumed that a car catches fire in thecar park and the fire size grows to a size of4MW and continues to burn for 20mins.During this time the ductless MV systemmust ensure that the smoke temperatureand visibility at a height of 1.7m from thefloor level are ≤ 250°C and ≥ 5mrespectively. A sensitivity study also needsto be considered to show the impact of onegroup of jet fan failure nearest to the fire.

Fig 1: Computational Domain of Basement 1 Car Park

SolutionComputational Fluid Dynamics (CFD) firesimulation was used to model a 4MW carfire in the car park for 20mins. The CFDresults will be used to predict the flow field,visibility and temperature at averagehuman head level of height 1.7m. This is toestablish how effectively the ventilationsystem can manage the smoke in the eventof a fire.

Fig. 3: Basement 1 Temperature Contour at 1.7m Height

The CFD study predicts that the there areno significant stagnation zones within thecar park. The visibility within the car park isat least 10m and the temperature is lessthan 100oC at 1.7m above the floor. Theregion where the temperature is more thanthe critical limit is only a small regionaround the fire, which is expected. Thus,the ventilation system for the car parkseems to be adequate.

Results

Fig 2: Computational Domain of Basement 2 Car Park

Fig. 4: Basement 2 Temperature Contour at 1.7m Height

Fig. 6: Basement 2 Visibility Contour at 1.7m Height

Fig. 5: Basement 1 Visibility Contour at 1.7m Height