Heat release rate curves

Total Heat Release From Wall Assemblies. We examined the total heat release from the wall assemblies as total heat contribution. The total heat release is obtained by integrating the area under the heat release rate curve with time and it is expressed in megajoules (MJ). The total heat release data from ignition to different times are shown in Table III for the wall assemblies. 

Figures 4.6—4.8 are the results for the stoichiometric propane-air flame. Figure 4.6 reports the variance of the major species, temperature, and heat release Figure 4.7 reports the major stable propane fragment distribution due to the proceeding reactions and Figure 4.8 shows the radical and formaldehyde distributions—all as a function of a spatial distance through the flame wave. As stated, the total wave thickness is chosen from the point at which one of the reactant mole fractions begins to decay to the point at which the heat release rate begins to taper off sharply. Since the point of initial reactant decay corresponds closely to the initial perceptive rise in temperature, the initial thermoneutral period is quite short. The heat release rate curve would ordinarily drop to zero sharply except that the recombination of the radicals in the burned gas zone contribute some energy. The choice of the position that separates the preheat zone and the reaction zone has been made to account for the slight exothermicity of the fuel attack reactions by radicals which have diffused into...

Figu re 8.2 Heat balance of a cooled CSTR, with the cooling term (straight line) and the S-shaped heat release rate curve. The working point is at the intercept. 

The left-hand side of the equation represents the cooling term, a linear function of temperature. In the right-hand side of the equation, we find the heat release rate by the reaction, where the rate constant k is an exponential function of the temperature. Thus, the heat release rate curve is S-shaped. The working point of the CSTR is located at the intercept of both curves (Figure 8.2). 

Reactions often follow nth-order kinetic law. Under isothermal conditions, for example, under conditions where the sample temperature remains constant, the heat release rate decreases uniformly with time. In the case of autocatalytic decomposition, the behavior is different an acceleration of the reaction with time is observed. The corresponding heat release rate passes through a maximum and then decreases again (Figure 12.1), giving a bell-shaped heat release rate curve or... 

FIGURE 12.7 Heat release rate curves for ABS and its nanocomposites with different MWNTs and MWNT-PDSPB content. (From Ma, H. et al., Adv. Fund. Mater., 18, 414, 2008. With permission.)... 

The heat release rate curves shown in Fig. 4A are consistent with the characteristic burning patterns of intermediate thick, non-charring samples (II). The PHRR values for PE-ZCHS-5 and PE-ZCHS-10 nanocomposites are reduced by 27 and 25% relative to the pure PE respectively. For smectite clay/polymer nanocomposites, reduction in PHRR has been shown to be correlated with nanodispersion of the additive in the polymer matrix (72). With HDS and related layered metal hydroxide additives, we have also only found PHRR reduction in the case of PVE with CHDS, a system with some... 

Figure 4. (A) Heat release rate curves for pure PE (empty circles), PE-ZCHS-5 (solid line), and PE-ZCHS-10 (bold line) from cone calorimetry measurements at 35 kW/m (B) Mass loss rate curves for pure PE (empty circles), PE-ZCHS-5 (solid line), and PE-ZCHS-10 (bold line).

The negative temperature dependences shown in these heat release rate curves are governed both by reaction rate and enthalpy. A relationship to the rate of reactant consumption over a range of temperatures is subject to constant enthalpy change. This requires there to be no change in reaction stoichiometry, which is not the case for the low-temperature oxidation of alkanes. 

For simulation, a rectangular compartment of 80 m long, 10m wide, 8 m high with opening at one end is considered. A section of the compartment is shown in Fig. 5 (half section of a symmetric compartment is shown). As the fire source a burning wood cribs is considered for this study of fire environment inside the compartment. The volume of the fire source is taken to be 9 m (3 m X 3 m X 1 m). The source is located 24 m from open end of the compartment, i.e. left portal. The heat release rate curve, as shown in Fig. 6 is taken from experimental results measured by Ingason et al. (1994) [19] on a wood crib fire imder natural ventilation condition as mentioned therein. 

A simplified model of ignition and burning of polymers which docs not require one to work with partial differential equations has been proposed by Rychly [49]. It was applied to the combustion carried out in a mass loss cone calorimeter system [50]. A series of simulations of heat release rate curves was performed for polymers with intumescent additives [51]. The model was also used for the prediction of limiting oxygen index (LOI) [52],... 

Figure 8.15 Heat release rate curves of hydromagnesite-containing composites Hy60 (30%LPDE -I-10% EVA + 30% ATH -I- 30% Hy), Hy55 (33.75% LPDE -I-11.25% EVA -I- 27.5% ATH + 27.5% Hy) and Hy/MMT50 (37.5% LPDE - -12.5% EVA + 30% ATH -I-15% Hy + 5% OMMT). From Haurie etal. [21, p. 1086]. With permission.

Figure 11.5 Heat release rate curves for PP and PP/Ceo nanocomposites at a heat flux of 35 kW/m. Reprinted with permission from Ref. [17]. 2008 lOP Publishing Ltd.

Figure 11.30 presents the heat release rate curves of polypropylene (PP) and its composites with 1 wt% CNTs or Ceo-rZ-CNTs. The incorporation of CNTs considerably reduced the peak heat release rate (PHRR) of PP (reduction around 66). At the same loading level. 

Figure 11.30 Heat release rate curves for pure PP, PP/1.0 wt% CNTs, PP/1.0 wt% Cgo- f-CNTs, and 1.0 wt% of physical mixture C o and CNTs at a heat flux of 35 kW/m. Note PHRR is peak heat release rate. Reprinted with permission from Ref. [20]. The Royal Society of Chemistry 2009.

FIGURE 10.9 Heat release rate curves of PTME-PA with siloxane and the POSS at 35 kW/m. (From Ref. 29.)... 

FIGURE 10.14 Heat release rate curves of St-BA and St-BA/GO nanocomposites. (From Ref. 41, copyright 2004, Elsevier, with pamission.) (See insert for color representation of figure.)... 

FIGURE 10.20 Effects of SWNT concentration on the heat release rate curve of PMMA-SWNT at 50 kW/m. ... 

The effects of the concentration of MWNTs in PP on the heat release rate curves of the nanocomposites are shown in Figure 10.25. The results show two distinct characteristics brought on by the addition of MWNTs first, there is a shortened ignition delay time with the PP-MWNT(0.5%), followed by an increase in ignition delay time with an increase in the concentration of MWNT second, there is a gradual increase in peak heat release rate above about 1% by mass of MWNT. A similar trend was observed for PMMA-SWNT nanocomposites (less obvious for PMMA-SWNT, due to a lower concentration of SWNT, as shown in Figure 10.20). The lowest heat release rate curve for PP-MWNT is achieved with about 1% by mass of MWNT compared to about 0.5% by mass of SWNT. The increase in peak heat release rate with concentration of MWNT above 1% appears to be due to an increase in thermal conductivity of the nanocomposite. ... 

Figure 15.11 Comparison of heat release rate curves and average rate (a) heat emission curves (b) for epoxy/IM-7, epoxy/IM-7/SWCNP, epoxy/IM-7/MWCNP, and epoxy/IM-7/CNFP. (Reprinted with permission from Wu etal. Copyright 2010 Elsevier Ltd.) (c) Original specimens for cone calorimeter test, (d) Schematic of the CNS-8 laminate, (e) Heat release rate of CNS-0, CNS-1, and CNS-8 laminates.

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