Numerical Simulation of Critical Velocity in Ventilation

Jabar Kesadian,Armen Adamian

doi:10.5539/mas.v11n2p19

Abstract

Given the importance of the safety and health of passenger’s in underground tunnels, analysis and simulation of fires in tunnels is to design a ventilation system. Longitudinal ventilation systems are widely used in tunnel ventilation and are one of the most important parameters for fire safety in this type of critical velocity system. Critical velocity of ventilation is minimum longitudinal velocity flow of air that prevents the smoke from the fire to the upstream flow.In this study, the effects of the distance between the fire source of the tunnel, obstacle before and after the fire, several sources of fire in the tunnel and ventilation shaft tunnels will be discussed on the critical velocity. Each effect parameter according to a correlation analysis of numerical results obtained using the solver FLUENT software Airpak and then the relationship between dimensionless critical velocity and dimensionless heat release are stated.

Highlights

Due to increasing population growth and urban and inter-urban roads need to use the tunnels to reduce traffic and shortening the path
The results of the study during the critical velocity and the smoke and ventilation shows that length of the tunnel is directly proportional to the size of the fire and ventilation speed and altitude varies inversely tunnel. (Hu, Huo & Chow, 2008) Effect of the fire source was investigated on critical velocity ventilation, so that the results showed that the critical velocity to stretch the fire along the length of the tunnel first increased and reduced and the maximum speed fire-square crisis does not happen. (Li & Chow, 2008)
If a fire occurs by two separate fires source, critical velocity decreases with increasing distance between them. (Tsai, Chen & Lee, 2010) Temperature distribution under the roof of the tunnel by twelve test (Hu et al, 2007) and was just a simulation. (Hu et al, 2006) so that the results show that temperature changes exponentially over and under the roof of the tunnel is reduced

Summary

Introduction

Due to increasing population growth and urban and inter-urban roads need to use the tunnels to reduce traffic and shortening the path. (Hu, Huo & Chow, 2008) Effect of the fire source was investigated on critical velocity ventilation, so that the results showed that the critical velocity to stretch the fire (gas burner) along the length of the tunnel first increased and reduced and the maximum speed fire-square crisis does not happen. Critical velocity air conditioning and heat release rate of two parameters on the distribution of smoke were investigated. [42] The dynamic effect of floating in a tunnel with longitudinal ventilation in order to study the effect of the fire source was investigated on critical velocity ventilation Results in such a way that non-dimension critical velocity has any clear dependence on the diameter of the fire source, the current density Buoyant and not ambient air. It is worth noting that in this study only investigated the effects of fire and combustion phenomena phenomenon is not modeling

The Governing Equations

Results

The Effect of Existence Obstacle before and after the Fire

Effects Existence Two Sources of Fire in the Tunnel

Conclusion