As we all know, graphite has conductivity, thermal conductivity, high temperature resistance and other properties. In fact, there is also the property of heat conduction. I believe you must be unfamiliar with it. Next, we will learn about graphite products together.

When there is a temperature gradient in graphite, heat flows from high temperature to low temperature. The parameter characterizing the thermal conductivity of graphite is thermal conductivity. Thermal conductivity is measured per unit time and per unit area

The proportional coefficient between the heat Q (heat flux) and the temperature gradient grad t.

q=– λ grad T

Where a negative sign indicates that the heat flow direction is opposite to the temperature gradient direction. Formula (1) is often referred to as Fourier's law of heat conduction. If the cross-sectional area perpendicular to the x-axis direction is Δ S. The temperature gradient of the material along the x-axis direction is DT / DX Δτ In time, it flows in the positive direction of the X axis Δ The heat of section s is: Δ Q. In the stable heat transfer state, formula (1) has the following form:

The legal unit of thermal conductivity is w • m – 1 • K – 1. For unstable heat transfer process, that is, the temperature varies with time. Objects that do not exchange heat with the outside world and have temperature gradients themselves will change over time,Graphite productsThe temperature gradient will tend to zero, that is, the temperature at the hot end will continue to decrease and the temperature at the cold end will continue to increase, eventually reaching a consistent equilibrium temperature. In this unstable heat transfer process, the temperature change rate per unit area of the object at any time is:

Where: τ Is time, ρ Is the density, CP is the constant pressure heat capacity of mass. λ/ρ CP is often called the thermal diffusivity or thermal conductivity of graphite, and the common unit is cm2 / s.

Heat conduction is realized by the movement of the heat conducting carrier. The heat conduction carriers of graphite include electrons, phonons (lattice vibration waves), photons, etc. The thermal conductivity of graphite can be expressed as the superposition of the contributions of various heat conducting carriers:

Where VI, Li and CI are the moving speed, average free path and specific heat capacity per unit volume of the heat conducting carrier I, respectively. Various heat conduction carriers of graphite interact and restrict each other. For example, phonons of different frequencies collide with each other and scatter, and phonons scatter with grain boundaries, lattice defects and impurities, affecting their average free path. Therefore, the heat conduction of graphite is a very complex physical process. Theoretically, it has been a long and hard work to accurately predict the thermal conductivity of various graphites and their changes with temperature, but only limited achievements have been made. Roughly speaking, at normal temperature and not too high temperature (less than 2000K), phonon thermal conductivity is dominant, and the thermal conductivity of electrons and photons can be ignored. At very low temperatures (less than 10k), the electronic thermal conductivity occupies a certain component. Photonic thermal conductivity does not appear until at very high temperatures (above 2000K). The thermal conductivity of graphite increases with the increase of its conductivity (see Wedman Franz's law). For more information, please pay attention toGraphite productswebsite