scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Effect of Parallel Curtain Walls on Upward Flame Spread Characteristics and Mass Loss Rate Over PMMA

TL;DR: In this paper, the effects of parallel curtain walls on the characteristics and mass loss rate of the upward flame spread over polymethyl methacrylate (PMMA) have been experimentally studied.
Abstract: The effects of parallel curtain walls on the characteristics and mass loss rate of the upward flame spread over polymethyl methacrylate (PMMA) have been experimentally studied. The experimental research variables were the sample size and separation distance of the curtain wall. In the experimental setup, a PMMA plate was attached to one of the curtain walls. The results were analyzed to assess the effect of the curtain wall separation distance on the flame height. The special condition of two curtain walls with only a small distance between them was also analyzed. Analysis of experiments with systematically varied distances between the curtain walls has provided insight into factors such as air entrainment and the chimney effect. The results show the flame height evolution trend with the separation distance, and a new correlation to predict the global mass loss rate of the PMMA plate under the influence of parallel curtain walls, which can potentially be used in curtain wall design through optimization of the separation distance given fire safety requirements and practical needs.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper , a series of experiments are performed using a vertical array of thin discrete fuels separated by heat absorbing inert materials of different thicknesses, and an existing model for flame spread rate is updated by incorporating the heat absorbing effects of the gaps.
Abstract: Flame spread over discrete solid fuels has been of key research interest in the past few decades. Most studies considered an array of discrete fuels separated by air gaps or heat-insulating inert materials. The effects of heat loss due to the discrete configuration are not well understood. The present study aims to bridge this knowledge gap. A series of experiments are performed using a vertical array of thin discrete fuels separated by heat-absorbing inert materials of different thicknesses. For comparisons, experiments are also performed using discrete fuels separated by air gaps and using continuous fuel. The flame base spread rate is found to be generally higher in discrete fuel than in continuous fuel configurations, due to a reduced fuel load per unit length. It is also found that the air and inert gaps have opposite effects on the solid burning rates. The air gaps break the no-slip boundary, allowing the laterally entrained buoyancy flow (normal to the sample surface) to push the flame closer to the samples. This leads to an enhanced heat flux on the sample surface and an increased solid burning rate. On the other hand, the inert materials retain the flow boundary profile and act as a heat sink during flame spread, thereby reducing the solid burning rate. As the inert thickness increases, flame spread rate and solid burning rate decrease. Based on these observations, an existing model for flame spread rate is updated by incorporating the heat-absorbing effects of the gaps. The correlation is validated using the experimental data.
Journal ArticleDOI
17 Mar 2023-Fire
TL;DR: In this article , the combustion behavior of thermoplastic materials is theoretically analyzed based on the empirical formulas and heat balance equations, such as the pyrolysis kinetics, ignition time, melting and dripping, flame, burning rate and mass loss rate, temperature and heat flow, gas products, and influencing factors.
Abstract: As thermoplastic materials are widely used in buildings, the fire hazards of thermoplastic materials are increasingly becoming a central issue in fire safety research due to their unique pyrolysis and melting mechanisms. In this paper, the features and common types of thermoplastic materials are introduced first. Then, the combustion behavior of thermoplastic materials is theoretically analyzed based on the empirical formulas and heat balance equations, such as the pyrolysis kinetics, ignition time, melting and dripping, flame, burning rate and mass loss rate, temperature and heat flow, gas products, and influencing factors. The influencing factors basically include the sample properties (width, incline angle, and thickness, etc.), the façade structure (sidewalls, curtain wall, etc.), the ambient conditions (altitude, pressure, and gravity, etc.), and the flame retardant treatment. Similarly, this study also illustrates the vertical and horizontal flame spread behavior of the thermoplastic materials and the influencing factors. The utilized methods include the experimental methods, the analytical methodologies, and the approaches for numerical simulation. Finally, the problems encountered at this stage and worthy of further study in the future are presented.
References
More filters
Book
11 Sep 1985
TL;DR: This paper introduced the physical effects underlying heat and mass transfer phenomena and developed methodologies for solving a variety of real-world problems, such as energy minimization, mass transfer, and energy maximization.
Abstract: This undergraduate-level engineering text introduces the physical effects underlying heat and mass transfer phenomena and develops methodologies for solving a variety of real-world problems.

13,209 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined and partially solved the problem of controlling the rate of combustion in large droplets, where the heat transfer and diffusion processes will have removed the chemical reaction zone far enough from the droplet to where it is less sensitive to the effects of the droplets itself.
Abstract: Fur Tropfchen, die groser als, sagen wir, 10−1 Zoll sind, entfernen Warmeleitungs- und Diffusionsprozesse die chemische Reaktionszone weit genug vom Tropfchen dorthin, wo sie fur die Effekte des Tropfchens selbst weniger sensibel ist, und daher die Verbrennungsgeschwindigkeit von den Warmeleitungs- und Massenprozessen selbst gesteuert wird. Dieses Problem wird in dieser Arbeit untersucht und teilweise gelost. For larger droplets - than say 10−1 inches - the heat transfer and diffusion processes will have removed the chemical reaction zone far enough from the droplet to where it is less sensitive to the effects of the droplet itself and hence the control of the rate of combustion will be the heat and mass transfer processes themselves. It is this problem that will be examined and partially solved in this paper.

257 citations

Journal ArticleDOI
01 Jan 2013
TL;DR: In this article, a thermally thick slab of polymethyl methacrylate was used to study the effects of the inclination angle of a fuel surface on upward flame spread and the influence of buoyancy-induced flows in modifying heat-flux profiles ahead of the flame front, which controlled flame spread, and in affecting the heat flux to the burning surface of the fuel.
Abstract: A thermally thick slab of polymethyl methacrylate was used to study the effects of the inclination angle of a fuel surface on upward flame spread. While investigation of upward spread over solid fuels has typically been restricted to an upright orientation, inclination of the fuel surface from the vertical is a common occurrence that has not yet been adequately addressed. By performing experiments on 10 cm wide by 20 cm tall fuel samples it was found that the maximum flame-spread rate, occurring nearly in a vertical configuration, does not correspond to the maximum fuel mass-loss rate, which occurs closer to a horizontal configuration. A detailed study of both flame spread and steady burning at different angles of inclination revealed the influence of buoyancy-induced flows in modifying heat-flux profiles ahead of the flame front, which control flame spread, and in affecting the heat flux to the burning surface of the fuel, which controls fuel mass-loss rates.

123 citations

Journal ArticleDOI
01 Jan 2013
TL;DR: In this article, the individual and combined influences of low pressure and aspect ratio on burning rate, temperature, puffing frequency, flame height and radiation for the two fuels were interpreted and formulated.
Abstract: Experiments on rectangular ethanol and n -heptane pool fires were conducted at different altitudes in Hefei (99.8 kPa) and Lhasa (66.5 kPa). The burners tested had the same fuel area of 900 cm 2 , but with aspect ratio of long side to short side ( n = l / w ) varied from 1 and 8. The individual and combined influences of low pressure and aspect ratio on burning rate, temperature, puffing frequency, flame height and radiation for the two fuels were interpreted and formulated. First, burning rate was found to be proportional to ambient air pressure under radiation control, the main reason is that radiative heat flux decreased with pressure due to the pressure affecting the soot absorption coefficient. Flame temperature slightly increased, leading to higher flame puffing frequency at low pressure. Flame height was almost insensitive to pressure as H ∝ p 0 . Second, for aspect ratio n , flame temperature was constant and independent of fuel type and burner shape. With increasing n , burner wall temperature increased at the long side, and decreased drastically at the short side, especially n = 8. This was attributed to the change of flame tilt and heating of the burner side, caused by variation of entrainment motion. Flame puffing frequency was found to increase with n as a function of f ∼ ( Δ T / T ∞ ) ( n + 1 ) / 2 n . The flame was observed to split into small clusters by enhanced asymmetric entrainment, and H decreased with increasing n as H ∼ ( 1 / n ) 2 / 5 Q ˙ 4 / 15 . Considering fuel differences, with increasing n , the burning rate of the ethanol pool fire decreased, and n -heptane showed the opposite trend.

111 citations