Technical challenege

Selecting appropriate ventilation equipments like supply fans, exhaust fans, and tunnel ventilation fans (TVF). Designing access and ventilation shafts. The ventilation system shall meet internationally accepted guidelines as specified by NFPA, SFPE, ASHRAE or PIARC.

As per these standards, the tenable environment should have:

i) Acceptable visibility levels.
ii) Acceptable temperature levels.
iii) Acceptable concentration of toxic air.

Engineering solutions

Using software tool Fire Dynamics Simulator (FDS):

i) Make a CFD model resembling the real scenario
ii) Analyze the problem with different specifications of the ventilation equipments.
iii) Select the optimum design which satisfies the overall goal.

Contours of smoke from the burning vehicle
after 1 minute time after start of fire


Contour plot of velocity magnitude at 6.5m
(at jet fan center) from the ground level

Result and conclusion

CFD results show that the design of the ventilation system is influenced by the following factors

i) Ventilation type (Longitudinal / Transverse)
ii) Tunnel geometry iii) Fire source location.
iv) Fire heat release rate (HRR),
v) Type of dominant burning materials
vi) Operation of the jet fans

Using these CFD results, an economical design of tunnel ventilation system was obtained with the following factors:

i) Achieved visibility levels are under acceptance criteria.
ii) No back flow of smoke near the fire source.
iii) Tunnel ventilation fans are sufficient to push the smoke from the tunnel efficiently & effectively for a given fire intensity.
iv) Improves the safety and security of humans.