Crystal algorithm of thermal conductivity

by:CBFI     2020-10-05
Crystal thermal conductivity and the calculation formula, the introduction of the

in metals and alloys, not only has the phonon crystal lattice thermal conductivity, there are electronic for heat conduction. Will supply of heat conduction electrons usually referred to as the coefficient of thermal conductivity of electronic, called by the instinct of the lattice wave transfer heat lattice thermal conductivity. For pure metal, electronics, thermal conductivity is greater than the lattice thermal conductivity. If the decision conductivity and electron scattering coefficient of thermal conductivity is the same process, can use a simple dynamic model.

in general, the coefficient of thermal conductivity of pure metal is bigger, they almost as a peak in the low temperature part, a peak corresponding to the analysis of temperature boundary such as lower than the peak temperature, the coefficient of thermal conductivity with lower temperature and decreased dramatically, and as the temperature is close to zero and also close to zero, as in the area is greater than the peak value of temperature, coefficient of thermal conductivity is as temperatures drop instead, also exists for metal and non-metal insulators with more regularity.

alloy the total thermal conductivity is very low, is also difficult to estimated in theory. With the reduction of temperature coefficient of thermal conductivity value usually also gradually decline. Part this is because the alloy thermal conductivity by phonon conduction, the other part was conducted by the conduction electrons, but these two points are small. The coefficient of thermal conductivity of metal under the condition of low temperature superconducting than normal value is smaller, this is because in the superconducting state electronics is not involved in the conduction of heat, use of this nature can make heat superconducting switch.

in addition, a kind of material of different purity has much effect on the thermal conductivity. Especially in the 10 - 30 k range, due to the chemical and physical purity smile changes can also cause the great change of the thermal conductivity. So in the design of low temperature experiment device as far as possible the choice of thermal conductivity values conform material. On refrigeration equipment selection, need to be aware of or coefficient of thermal conductivity, and the product quality, this is the reason why product is popular, not only ensure the use of product quality, more emphasis on product cooling effect, on the premise of guarantee the refrigeration effect, constantly improve and perfect, beyond the self.
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