# Thermal Effusivity Tester (TET)--A New Device to Determine Thermal Effusivity of Textiles
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Sample No.**} & \multicolumn{2}{c}{**1**} & \multicolumn{2}{c}{**2**} & \multicolumn{2}{c}{**3**} & \multicolumn{2}{c}{**4**} & \multicolumn{2}{c}{**5**} & \multicolumn{2}{c}{**6**} & \multicolumn{2}{c}{**7**} & \multicolumn{2}{c}{**8**} & \multicolumn{2}{c}{**9**} \\ \hline \(t\)-Test & 26.5 & x & 0.5 & \(\surd\) & 2.3 & x & 5.4 & x & 1.7 & 0.6 & 0.3 & 0.3 & 3.9 & x & 2.1 & x \\ \hline t\({}_{\text{n1+n2-2}}\) (\(p=0.05\)) & 2.00 & x & 2.02 & 2.03 & x & 2.02 & 2.09 & \(\surd\) & 2.09 & \(\surd\) & 2.09 & \(\surd\) & 2.09 & x & 2.09 & x \\ \hline t\({}_{\text{n1+n2-2}}\) (\(p=0.01\)) & 2.66 & x & 2.70 & \(\surd\) & 2.73 & \(\surd\) & 2.70 & x & 2.86 & \(\surd\) & 2.86 & \(\surd\) & 2.86 & \(\surd\) & 2.86 & \(\surd\) \\ \hline \end{tabular}
\end{table} 
Table 7: \(t\)-test statistics for comparison of Alambeta’s and TET’s effusivity results. effusivity has already been emphasized in earlier studies [7]. While the Alambeta device works with a pressure of 200 Pa, the TET device adapts its pressure on the fabric to compress the fabric to 10% of the pre-measured thickness. TGi, on the other hand, applies a fixed weight of 0.5 kg on a multilayered sample. This results in different compression forces on the sample, of which the logical consequence is thinner fabric, higher density and higher conductivity. Cotton fiber has a higher crimp and hence more volume and resilience in the fabric. A comparable effect can be expected in fabrics with elastane. This makes the measurement more sensitive to the pressure force applied by the device than the measurement on flatter fabrics. Woven fabrics show higher thermal effusivity due to their smooth surface, which provides more contact points with the device surface than the knitted fabrics. In total, the result shows that the thermal and mechanical setting of TET provide results close, or at least comparable to, such provided by other commercially available devices. Figure 6 shows the results for thermal conductivity. A fair agreement between Alambeta and TET results can be seen, while TGi measures much higher conductivities on the four tested fabrics. Also, here, the applied pressure seems to play a decisive role in the obtained result. The higher the applied pressure, the thinner the fabric and hence the higher the measured conductivity. Due to the higher pressure applied in TGi, a significantly higher thermal conductivity was measured. Fabrics 1 and 4 show large differences among the three devices, most probably due to their resilient character. In textile apparel and home application, thermal insulation/conductivity is usually measured with other means, such as the compression-free \"Sweating Guarded Hot Plate\" test according to ISO 11092 [15]. Figure 7 shows a comparison of TET results with KES-f Thermo Labo (Q\({}_{\text{max}}\)) results for 10 knitted and woven fabrics. Having different units in this case, the fabrics are compared in the trends or the ranking according to the value measured. Similar trends are obtained for most samples. The Pearson correlation factor between the two methods was 0.9. Figure 6: Thermal conductivity measured with Alambeta, TGi and TET; in mean values \(\pm\) standard deviation.