كلية الهندسة.

Faculty of Engineering.

A thesis submitted in partial Fulfillment of The requirements for the Degree of DOCTOR OF PHILOSOPHY in Mechanical Power Engineering.

Includes Bibliographic Referances,P:132:141.

ABSTRACT
Fire suppression systems are an extremely important part of every building that ensures the safety of the occupants and limits damage due to fire. Water mist systems use pressurized nozzles which release water droplets of different fire sizes. The mist encapsulates the fire and as it turns to vapor, removes heat from the source. As the mist turns to steam, it expands immensely forcing oxygen away from the flame. This denies the fire the necessary oxygen to be able to sustain itself. Fire suppression by using water mist is investigated in this study.
Full scale model is set up for the purpose of predicting the geometry of fire spread and water mist particles distribution. The results are based on the full scale model simulation for several water mist nozzle characteristics. The model is subjected to study different nozzle features. The obtained results are similar to other published results.The study is carried out using Fire dynamic simulator (FDS) combined with PYROSIM and SMOKEVIEW programs. These programs, to achieve the model of compartment fire scenario and fire extinguishment requires investigating and determining heat and gases concentrations.
In this study two types of fire compartment are presented, normal room and hanger (inclined surface). Various water mist properties with the same model are studied. The effect of water mist nozzle configurations on fires suppression through study the effectiveness of droplet size is varied from 50 μm to 1000 μm, spray cone angle, nozzle discharge and nozzle operating pressure are illustrated in case of hanger. The water mist droplet speed, water mist flux, droplet size and droplet distribution are discussed in the case of normal room.
It can be concluded that the water mist nozzle configurations in a fire compartment affects on the fire extinguishing time, the temperature and gas concentration in the hanger. The spray cone angle 60ο better than 120ο for fire suppression, also the O2 concentration for a water mist with the smaller size droplet 50 μm is reduced however the larger size droplet 750 μm is still kept. Also The water mist droplet movement, particle size and droplet distribution play a vital role to suppress the fire.
At last due to the FDS code development and model validation, the capability of FDS to predict the performance of fire suppression by using water mist systems has been significantly improved. Chapter 1
INTRODUCTION
1.1 Introduction
The research on fire suppression (fire safety) has captured more and more attentions worldwide; this is because of the heavy losses of property and people that result from these fires.
Statistics from the National Fire Protection Association help support the fact that tall buildings are generally among the safest type of structures [1]. Less than one percent of fatalities due to fires occur in high-rise buildings, and only a small number of major fires reported damages over $250,000 in tall buildings. The spread of fire, smoke and gases between floors should try to be limited in high-rise buildings. A study conducted in 1971 showed that ten percent, or 5 out of the 51 high-rise building fires studied, spread outside the windows to the upper floors.
Fire safety regulations can have a major impact on many aspects of the overall design of a building, including layout, aesthetics, function, and cost. Rapid developments in modern building technology in the last decades often have resulted in unconventional structures and design solutions. The physical size of buildings increases continually; there is a tendency to build large underground car parks, warehouses, and shopping complexes. The interior design of many buildings with large light shafts, patios, and covered atriums within buildings connected to horizontal corridors or malls introduces new risk factors concerning spread of smoke and fi
Fire suppression by using water mist is widely considered to be an alternative to gaseous fire suppression agents. A lot of commercial activity has occurred in the last years to develop technology for fire suppression systems based on water mist. Although researchers in the 1950's recognized the dominant mechanisms of extinguishment, recent experimental work has particular fire scenario, and is essential for the development of algorithms for computer models of water mist suppression systems.
Considerable attention was given to studying the potential for fire suppression with water mist in the 1950's. The use of very fine water sprays to extinguish fires has received much renewed attention in the last years.
This chapter reviews existing fire, firefighting methods and practice in particular the use of water mist as a fire suppression system.

Includes CD copy for The Thesis

Text In English and Abstract in Arabic .