design fires for smoke control dr. john h. klote pe fire and smoke consulting...
TRANSCRIPT
Design Fires for Smoke Control
Dr. John H. Klote PEFire and Smoke Consulting
www.SmokeControlExpert.com
Learning Objectives• Provide an understanding of fire
growth, flashover, fully developed fire and fire decay.
• Provide an overview of the basic concepts of developing design fires for smoke control systems.
• Extensive Treatment of All Aspects of Smoke Control
• For more information about design fires, see Chapter 5 “Fire Physics & Design Fires”
Design Fires
• Used for Atrium Smoke Control and Tenability Systems
• IBC– No Prescribed Design Fires– Requires Analysis of Design Fires
• Many Engineers – New to Design Fires
• This Talk: – Overview of Analysis of Design Fires– Focus on Highlights
UK Information on Design Fires
• Industrial & Warehouse (not high racked) -1990 Smoke Ventilation Association Guide:– Sprinklered Steady Fires - 3m x 3m to 9m x 9m.– Unsprinkleres Steady Fires – 2 Times as Big
• Steady Fires in Car Parks – BS 7346-7• Guidance for Offices & Hotels – BS 7346-4 and
5 and in BR368• General Information on Specific Objects:
– BS 7974 (UK fire engineering standard) – BRE design fires database CD
Design Fires
• Normally Most Important Property - Heat Release Rate (HRR)
• Other Properties (toxic gases, reduced visibility, etc.) - Tenability Systems
• For simplicity - Only Discuss HRR
• HRR of a Design Fire:– Steady – Unsteady
• Steady HRR – Peak of Unsteady HRR
Fully Developed Fire
• Called “Ventilation Controlled Fire”• Room with One Opening
– HRR Controlled by Opening Size – HRR Equation
1/ 21260 w wQ A H
where Q = HRR (kW) Aw = area of opening (m2), Hw = height of opening (m).
HRR Measurement
• Oxygen Consumption Calorimeters– HRR per unit O2 Consumed – Almost
Constant (13.1 MJ per kg of oxygen + 6%)– Open Air Calorimeter – Room Calorimeter
Design Fires
• Normal Fuels - Objects Planned for Space• Transient Fuels - In a Space Temporarily
– Examples: Trash, Stacked Wood Pallets, Furniture After Delivery, etc.
• Atrium Fires– Normal & Transient Fuels– No Benefit of Sprinklers (Ceilings > 35 – 45 ft)– Transient Fuels: Suggest Min. 2000 Btu/s
• Non-Atrium Fires– Normal & Transient Fuels– Fires w/ Axisymmetric Plume – CFAST– Shielded Fires (NIST & NRCC Models)
