Project Overview

I conducted an in-depth computational fluid dynamics (CFD) simulation study of an existing Smoke and Heat Exhaust Ventilation System (SHEVS) in an underground parking facility. The primary focus was to evaluate the system’s effectiveness in post-fire smoke clearance and analyze its performance across various spatial and temporal parameters.

Simulation Methodology

The analysis utilized advanced CFD modeling to simulate smoke behavior and ventilation system performance under post-fire conditions. Key parameters monitored included:

• Smoke density distribution
• Airflow patterns
• Clearance time metrics
• Zone-specific performance
• System response timing

Detailed Performance Analysis

Safety-First Design Implementation

A critical feature of the SHEVS system is its 4-minute activation delay. This intentional delay serves as a crucial safety measure, preventing:

• Premature smoke distribution
• Fire spread through forced ventilation
• Compromised evacuation routes The delay ensures occupants have sufficient time to evacuate before ventilation begins, prioritizing life safety over property protection.

Total System Performance

The simulation revealed comprehensive performance metrics:

• Complete smoke clearance achieved in 45 minutes
• Primary spaces cleared significantly earlier
• 37-minute mark showing substantial improvement
• Progressive clearance patterns from main areas to periphery

Zone-Specific Analysis

High-Performance Areas

The system demonstrated excellent efficiency in:

• Main thoroughfares
• Open parking areas
• Primary circulation routes
• Areas directly in the jet fan’s airflow path

Challenging Zones

Several areas showed reduced clearance efficiency:

1. Corner Regions
   • Reduced airflow velocity
   • Extended clearance times
   • Smoke persistence
2. Wall-Adjacent Areas
   • Limited air circulation
   • Slower smoke dissipation
   • Flow pattern complications
3. Buffer Zone Dynamics
   • Complex airflow patterns near exit ramp
   • Interaction between architectural features and ventilation
   • Impact of obstacles on smoke clearance

Airflow Dynamics Assessment

Central Jet Fan Performance

The centrally positioned jet fan demonstrated:

• Strong directional airflow toward exits
• Effective smoke channeling in primary zones
• Consistent performance in main areas

Flow Pattern Analysis

Detailed observation of airflow patterns revealed:

• Velocity variations near obstacles
• Impact of architectural features on flow
• Creation of localized circulation patterns
• Edge effects near walls and corners

Technical Insights

System Efficiency Factors

The analysis identified key factors affecting system performance:

1. Architectural Constraints
   • Building geometry impact
   • Obstacle placement
   • Ventilation pathways
2. Flow Dynamics
   • Velocity distribution
   • Pressure gradients
   • Turbulence patterns
3. Time-Dependent Behavior
   • Initial response characteristics
   • Progressive clearance patterns
   • Final phase efficiency

Performance Optimization Opportunities

The simulation highlighted potential areas for system enhancement:

• Corner and wall area treatment
• Buffer zone flow management
• Obstacle impact mitigation
• Flow pattern optimization

Comprehensive Findings

The SHEVS system demonstrates effective performance in its primary function of post-fire smoke clearance. The 45-minute total clearance time, with significant improvement by 37 minutes, indicates robust overall efficiency. The intentional 4-minute activation delay successfully balances safety requirements with clearance objectives.

While main areas show excellent clearance characteristics, the system faces challenges in specific zones, particularly:

• Areas with limited airflow
• Corner regions
• Wall-adjacent spaces
• Buffer zones near exits

The central jet fan effectively directs smoke toward exits, though its efficiency is impacted by architectural features and obstacles that affect airflow patterns and velocities.

Conclusion

This detailed simulation analysis provides valuable insights into the SHEVS system’s performance characteristics. The study confirms the system’s capability to effectively clear smoke post-fire while identifying specific areas where airflow dynamics create challenges. These findings contribute to understanding both the system’s strengths and areas where potential optimizations could be considered.