# Study of the Influence of Heat Flow on the Time to Ignition of Spruce and Beech Wood
## 3 Results and Discussion  
The results of the time to ignition measurements for the spruce and beech wood samples are presented in Table 2, and the average time to ignition values (TTI) depending on the distance from the heat source are shown in Figure 6. This figure provides the time to ignition values of spruce wood samples at a radiant panel power of 5 kW and sample placements at the distance of 50, 70, and 100 mm from the electric radiant panel. At a radiant power of 5 W, both the spruce and beech wood exhibited flaming combustion for all of the heat flux values, except for the last sample of beech wood which was placed at the distance of 100 mm, corresponding to a heat flux value of 64 kW\(\cdot\)m\({}^{-2}\). Non-flaming combustion was observed for 15 min. Examples of flaming (Figure 6a) and non-flaming (Figure 6b) combustion of beech wood at radiant power of 5 W are shown in Figure 6.  
For the spruce wood with a radiant panel power of 10 kW, flaming combustion of the sample occurred at distances of 100 mm and 150 mm (corresponding to heat fluxes of 90 and 62 kW\(\cdot\)m\({}^{-2}\)). At a distance of 200 mm from the radiant heat source (heat flux of 47 kW\(\cdot\)m\({}^{-2}\)), flaming combustion of the sample did not occur, but the effect of the heat flux manifested as non-flaming combustion. Figure 5: Measured heat flux values depending on the power of the electric radiant panel and the distance from the radiant heat source. Red colour represents 5 kW power, and blue represents 10 kW. Similar behaviour was also observed with the beech wood samples, where at a heat flux of 47 kW\(\cdot\)m\({}^{-2}\), non-flaming combustion occurred. We observe an increase in time values with increasing distance when comparing the obtained values of tSP for individual heat fluxes (Figure 6). Interestingly, different tSP values were observed when the radiant panel power was evaluated using a distance of 100 mm for both the 5 and 10 W powers (Table 1). On the contrary, at the distance of 150 mm and a radiant panel power of 10 kW, there was an equal time to ignition (Figure 6) for both the beech and spruce samples. Thanks to the abundance of the obtained experimental outputs, it was possible to utilize the statistical method ANOVA to monitor the significant influence of selected factors (wood species, radiant panel power, distance from the heat source) on the experimentally determined time to ignition (Table 3). \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Radiant Power (kW)**} & **Distance** & **Radiant** & \multicolumn{2}{c}{**Spruce**} & \multicolumn{2}{c}{**Beech**} \\ \cline{3-8}  & **from the Heat Source (mm)** & **Radiant** & **Density** & **Time-to-** & **Flame** & **Density** & **Time-to-** & **Flame** \\ \cline{2-8}  & **Heat Source (km\(\cdot\)m\({}^{-2}\))** & **(kg\(\cdot\)m\({}^{-3}\))** & **Ignition (s)** & **(+/-)** & **(kg\(\cdot\)m\({}^{-3}\))** & **Ignition (s)** & **(+/-)** \\ \hline \multirow{3}{*}{5} & 50 & 91 & 420.38 \(\pm\) 50.96 & 9 \(\pm\) 1.54 & + & 701.41 \(\pm\) 30.67 & 22.4 \(\pm\) 7.49 & + \\ \cline{2-8}  & 70 & 74 & 412.63 \(\pm\) 54.34 & 15.2 \(\pm\) 2.92 & + & 695.87 \(\pm\) 21.23 & 30.2 \(\pm\) 4.16 & + \\ \cline{2-8}  & 100 & 64 & 421.7 \(\pm\) 30.46 & 38.4 \(\pm\) 3.26 & + & 688.83 \(\pm\) 17.68 & X & \(-\) \\ \hline \multirow{3}{*}{10} & 100 & 90 & 420.05 \(\pm\) 52,18 & 16.2 \(\pm\) 1.6 & + & 698.74 \(\pm\) 16.82 & 23.6 \(\pm\) 1.62 & + \\ \cline{2-8}  & 150 & 62 & 420.50 \(\pm\) 52.74 & 82.6 \(\pm\) 10.57 & + & 697.536 \(\pm\) 26.76 & 82.2 \(\pm\) 10.57 & + \\The evaluation of the obtained values was verified using a mean and standard deviation dot plot for each group of results (Figure 7). The heterogeneity of the variance was demonstrated, which was confirmed by the [PERSON]'s test for the homogeneity of variance that was performed, with results of \(p\)-value = 0.0000 and F = 8.110353.