Conclusions

Based on the results obtained in the thermal simulations carried out the following conclusions are deduced:

• The thermal conductivity of the material to be studied clearly determines the magnitude of the temperature gradient expected in the sample.
• Thermal gradients in the sample are greater at low operating temperatures.
• This fact is due to the dependency of the thermal conductivity with the temperature, which gets reduced as the temperature increases, especially at temperatures above 400ºC.
• From a certain value of power brought by the cylinder on (between 150 and 200 W) the temperature gradient in the sample gets slightly increased. The factor that causes this phenomenon is the temperature distribution inversion that takes place in the sample. The distribution becomes symmetric as the temperature rises until it gets inverted, from this point on the gradient starts to increase again.

The modification of the alumina tube geometry has a noticeable positive impact on the thermal behavior of the sample.

• The new alumina support minimizes the value of the themperature gradient in the sample. The greatest gradient relative reductions are obtained at an operating point between 75 W and 150 W generated by the cylinder and the maximum values are shown in the table below:
$\boldsymbol{\lambda}_{\mathbf{sample}}$ [W/m·K] 2 20 100
ΔT reduction [%] 69% 77% 80%
• On the other side, the greatest absolute reductions of the temperature gradient in the sample are achieved at low operating temperatures. The maximum values of absolute reduction of the gradient are shown in the following table:
$\boldsymbol{\lambda}_{\mathbf{sample}}$ [W/m·K] 2 20 100
ΔT reduction [ºC] 16.65 6.35 1.71