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Journal ArticleDOI

Upward Flame Spread Over an Array of Discrete Thermally-Thin PMMA Plates

01 May 2021-Fire Technology (Springer US)-Vol. 57, Iss: 3, pp 1381-1399
TL;DR: In this paper, the authors investigated the upward flame spread over a homogenous PMMA plate and an array of discrete thermally thin PMMA elements, and the experimental results showed that the flame spread rate peaks in the case of discrete PMMA element with a fuel coverage around 80% rather than 100% (the homogenous case).
Abstract: Experiments and theoretical analysis were conducted to investigate the upward flame spread over a homogenous PMMA plate and an array of discrete thermally thin PMMA elements. In the experiment, a digital video camera was used to record the flame spread process. An electronic balance and thermocouples were adopted to monitor the mass loss and pyrolysis front position, respectively, as a function of time. In the theoretical analysis, the mass loss rate of PMMA was correlated to the heat transfer during flame spread. The experimental results show that the flame spread rate peaks in the case of discrete PMMA elements with a fuel coverage around 80% rather than 100% (the homogenous case) because the gap with an appropriate spacing between neighboring elements accelerates the flame spread. However, the flame cannot spread over an array of discrete fuels at a coverage of 50% or smaller where the gap is too large to allow effective heat transfer required for flame spread. A smaller coverage of PMMA results in a larger mass loss rate per area since the gaps between elements can entrain more air to promote the burning. A logarithmic relation, that can well describe the mass loss rate as a function of PMMA coverage, was proposed based on the theoretical analysis and the fitting of experimental measurements.
Citations
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Journal ArticleDOI
24 Apr 2022
TL;DR: A comprehensive review of biomedical polymers can be found in this paper , where the authors summarize the most recent advances in the synthesis and application and discuss the comprehensive understanding of their property-function relationship for corresponding biomedical applications.
Abstract: Biomedical polymers have been extensively developed for promising applications in a lot of biomedical fields, such as therapeutic medicine delivery, disease detection and diagnosis, biosensing, regenerative medicine, and disease treatment. In this review, we summarize the most recent advances in the synthesis and application of biomedical polymers, and discuss the comprehensive understanding of their property-function relationship for corresponding biomedical applications. In particular, a few burgeoning bioactive polymers, such as peptide/biomembrane/microorganism/cell-based biomedical polymers, are also introduced and highlighted as the emerging biomaterials for cancer precision therapy. Furthermore, the foreseeable challenges and outlook of the development of more efficient, healthier and safer biomedical polymers are discussed. We wish this systemic and comprehensive review on highlighting frontier progress of biomedical polymers could inspire and promote new breakthrough in fundamental research and clinical translation.

52 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of air gap and thickness of wood chips in the fire propagation mechanism by experimental investigating the mass loss rate (MLR), flame spread rate (FSR), total burning duration (TBD), and the flame characteristic length (MFL).
Abstract: The fire hazard has frequently destroyed wooden cultural heritages. The discrete wood chips allow fire propagation quickly in practice. This study aims to clarify the effect of air–gap and thickness of wood chips in the fire propagation mechanism by experimental investigating the mass loss rate (MLR), flame spread rate (FSR), total burning duration (TBD) and the flame characteristic length (MFL). The 2 cm long and 10 cm wide wood chips were uniformly installed on a vertical sample holder. The air–gap distance and the thickness of wood chips changed from 1.0 cm to 3.0 cm and 1 mm to 4 mm, respectively. The flame spreads across with the wood grain orientation. The experimental result shows that FSR and MFL are sensitive to the air–gap distance. It is concluded that, TBD versus thickness of the sample is linear with an equation TBD (s) = 7.7 × thickness (mm) + 18.6. Concerning the fixed thickness of the sample, the TBD varies a little from the air–gap distance. The MFL increases to a peak then decreases to a low value as the thickness differing from 1 mm to 4 mm. It is observed that the air–gap makes little contribution to the TBD. The MLF history as the air–gap distance changing from 1.0 cm to 3.0 cm indicates that the distance of air–gap imposed little effect on the MFL. The a-MLR profiles mainly depend on the thickness of the sample.

8 citations

Journal ArticleDOI
TL;DR: In this article, the authors used PMMA blocks as experimental materials to carry out upward flame spread experiments with different air gaps (0-18 cm) to analyze changes in burning rate, flame shape, flame height and pyrolysis front position.

6 citations

Journal ArticleDOI
TL;DR: In this paper , the effect of structure factor (the ratio of sidewall width to back wall width) and fuel coverage on PMMA flame spread in a vertical channel of building facades was experimentally studied.
Abstract: Building fire occurs frequently in the vertical channel of building facades, which leads to rapid flame spread and overflow flame at the window interval, causing huge losses. Upward flame spread over discrete polymethyl methacrylate plates (PMMA) in a vertical channel of building facades was experimentally studied in this work. Meanwhile, the coupling effect of structure factor (the ratio of sidewall width to back wall width) and fuel coverage (the ratio of PMMA height to the total height of PMMA and window interval) on PMMA flame spread was revealed. The results showed that the maximum temperature at 3 cm away from the surface of PMMA first rose and then dropped with the increase of the structure factor. However, the maximum temperature at the center of the vertical channel decreased with the increase of the structure factor. For different fuel coverage, the temperature of the window overflow flame and the back wall gradually increased with the increase of the structure factor. When the fuel coverage was 0.52–1, the increase rate of flame height decreased with the decrease of fuel coverage. A model for predicting the flame height was established, and its prediction results agree well with the changing trend of experimental results of the flame height under different structure factors and fuel coverages. This work is beneficial for fire safety assessment of PMMA in the vertical channel with window intervals.

2 citations

Journal ArticleDOI
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.

2 citations

References
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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

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11,281 citations

Journal ArticleDOI
TL;DR: Data for estimating the burning rate and heat output of large pool fires (diameter ≳ 0.2 m) are compiled and computational equations presented and a large scatter is noted.
Abstract: Data for estimating the burning rate and heat output of large pool fires (diameter ≳ 0.2 m) are compiled and computational equations presented. Since a large scatter in the reported data is noted, attention is also focused on areas where further research is most needed in order to improve predictability.

404 citations

Journal ArticleDOI
01 Jan 1985
TL;DR: In this article, the dependence of flame height on a dimensionless heat addition parameter shows a transition for values of the parameter around unity, indicating that the initial diameter of the fire does not affect the length of the flame whereas for short flames, initial geometry becomes important.
Abstract: Natural gas diffusion flames stabilized on 0.10, 0.19 and 0.50 m. diameter porous bed burners have been studied for heat release rates ranging from 10 to 200 kW. Flame heights were measured from video tape recordings and by eye averaged techniques. The dependence of flame height on a dimensionless heat addition parameter shows a transition for values of the parameter around unity. For flames taller than three burner diameters, the initial diameter of the fire does not affect the length of the flame whereas for short flames, initial geometry becomes important. Another prominent feature of these flames is the presence of large scale axisymmetric structures which are formed close to the burner surface with more or less regular frequency and which rise through the flame region. These structures are responsible for the fluctuations of the flame top and strongly influence the geometry of the flame.

294 citations