Abstract
According to recent UN reports, it is estimated that more than one billion people live in informal settlements globally, exposing them to a large potential fire risk. In previous research, it was found that the main fire spread mechanism between dwellings is the external flaming (plume) and radiative heat fluxes from the vertical openings at the dwelling of origin to the surroundings. In this paper, an experimental and numerical study was conducted to quantify the effect of adding horizontal roof openings to the design of informal settlement dwellings to reduce the fire spread risk by decreasing the length of flames and radiation from the external plumes at the vertical openings. In total, 19 quarter scale ISO-9705 compartment fire experiments were conducted using an identical fuel load (80 MJ/m2) of polypropylene and were used to validate a physical computational fluid dynamics model for future studies. Five different total horizontal openings areas (0.0025, 0.01, 0.04, 0.09, and 0.16 m2) were investigated using two horizontal openings designs: (1) four square openings at the four corners of the compartment and (2) one slot cut at the middle of the compartment. It was found that adding horizontal openings decreased the average heat flux measured at the door by up to 65% and 69% for corner and slot cases, respectively. Heat flux reductions were achieved at opening areas as low as 0.01 m2 for slot cases, whereas reductions were only achieved at areas of at least 0.09 m2 for corner cases. The Computational Fluid Dynamics (CFD) model was validated using the experimental results. It successfully captured the main fire dynamics within the compartment in addition to the values of the external radiative heat flux. Further, a new empirical ventilation factor was generated to describe the flow field through both openings configurations which showed strong coupling with the inlet mass of fresh air to the compartment.
Highlights
Urbanization is one of the most critical global phenomena in today’s world
Different physical and chemical phenomena occur during compartment fire experiments, e.g., ignition, combustion, radiation, flame spread, and many others
It appears that time to “flashover” decreases as ventilation area increases, the data have a significant scatter (R2 = 0.1789). This suggests that adding horizontal openings accelerates fire growth, but this is as yet an unreliable correlation and so further work is required on this subject
Summary
Urbanization is one of the most critical global phenomena in today’s world. Urbanization poses immense burdens on infrastructure, essential services, life quality, and safety. It was assumed that all the hot smoke will be leaving the compartment in straight lines through the horizontal opening, while the vertical opening will only pass cold air one way to the inside o compartment Based on these assumptions, a fictitious ventilation factor otfh2a4t couple tween the vertical and horizontal opening was proposed as the following: on these assumptions, a fictitious ventilat(ivon)facto=r thvat+co2u.p3lAes b√ehtween the vertical and hworhizeornetalAopeinsitnhgewaarseparoopf othseedhaos rtihzeofnoltlaolwoipnge:ning, and h is the vertical distance from height of deed not ctohveewr ainlldtohwe roepalenca(ivnsefg)sfticocet nt=haevrifro+osoa2f.s3oApfrhte√hsehencotemdpinarFtmigeunret.sT2h–e4s, ewahsesrue(m2t)hpetihoontssd wehxeirtes Athheiscothme paraeratmofetnhtevhioaribzotnhtatlhoepveneirntgic,aalnadnhdishtohreizvoenrttiacal lodpiestnainncgesf;rothmemaiird-flow is n hsetigrahitgohftthlienwesi,nadnowd ionpdeneeindg tthoetrhee croooufldofbtheemcoumltpipalretmveenrtt.icTahleoser ahsosurimzopntitoanlsodpoenings i insdaemede ncootmcpovaerrtmalel ntht.e real case scenarios as presented in Figures 2–4, where the hot snmotoiknesTetrxoaitifsguhthrttelhicneoerms,tpahanirsdtmbineadnseteevdoiafthbkeorntehocwtohuleeldvdebgreteicmoaulnaltnhipdolerhiovzreoirzntoitcnaatllaoloroppheeonnriiiznnoggnsst;atilhnoepcaeoirnmiflnpogwasriitnsments, i thperseasmenetcostmupdayrtma eqnut.arter scale IS0-9705 room
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