Influence of U-shaped structure on upward flame spread and heat transfer behaviors of PMMA used in building thermal engineering

Abstract

Both experimental and theoretical study on upward flame spread and heat transfer behaviors of PMMA (polymethyl methacrylate) under different U-shaped structure factors (Π) was conducted. The main results are as follows. The progress of pyrolysis front is used to determine flame spread rate since the flame front is more fluctuating than pyrolysis front. The flame spread rate is stable for 30 cm-length PMMA in this work. For Π<1, the flame spread rate increases as Π rises. For Π≥1, the flame spread rate tends to be stable. Based on heat transfer analysis, two models are established to predict flame spread rates with different Π for laminar and turbulent flame, respectively. Compared with experimental results, the prediction error is lower than 9%, within acceptable range of engineering. The prediction accuracy of the present model is better than that of previous model. In addition, theoretical correlation between the flame height and pyrolysis length is xf=1.639xp. Predicted flame heights are basically consistent with experimental results when Π = 0.4 or Π = 1.6. This work is beneficial for safety evaluation and optimization design of building thermal engineering using PMMA.