Staff of the Department of Thermophysics is involved in the development of new innovative class of the testing methods – transient methods for measuring of the thermophysical properties of materials. Principle of this class of methods is based on generation of a small heat disturbance inside a specimen and the measuring of the following temperature response. Methods are included into this class where measuring probes are embedded into the material thus surface interfering effects are suppressed. Table 1 gives an overview of the basic experimental arrangement of the transient methods. Table 1.: Transient methods and the corresponding parameters that can be determined by particular method. |

Theory and the methodology of the following transient methods were worked out in our department:
Pulse transient method:
The thermophysical parameters are determined according used model. Ideal model is used that assumes: -
nonlimited specimen -
planar heat source of the negligible thickness -
ideal thermal contacts -
heat pulse in a form of Dirac’s pulse.
Such model is characterized by formulas that describe the temperature response
where
Two procedures can be used for calculation of the thermophysical parameters:
Interfering
effects:
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Heat
source and the heat loss effects.The heat source and the heat loss effects deform the temperature response at the short times and at the long times. Instead of ideal function (1) or (2), the function (6) is used for fitting (case of heat loss effects). (6) where J
are Bessel functions s=H /
λ
and a_{1}(x)_{n
}are the roots
of the equation:
Heat pulse
width effect.The real heat pulse width deforms the temperature response. Instead of ideal function (1) or (2), the function (7) is used for fitting. (7) where
The real heat source capacity effect shifts in a way shown in upper figure the temperature response. Instead of ideal function (1) or (2), the function (8) is used for fitting. (8) where and
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