热质的运动与传递-微尺度导热中的热质动能效应

基于热质(热量的当量动质量)的概念,通过建立和分析热质的运动方程得到了反映热质动能变化的稳态导热微分方程,表明Fourier导热定律只有在热质的动能变化相对热质势能变化很小而可以忽略时才成立;在高热流密度和低温的情况下热质的动能变化不可忽略,这种动能效应表现为热流密度和温度梯度不再成线性关系.动能效应也导致Fourier导热定律不能通过热流和温度梯度准确地获得物体的导热系数,本文基于热质运动方程给出了导热系数动能效应的修正式.最后针对高热流密度和低温一维稳态导热进行了分子动力学模拟验证.

KINETIC ENERGY EFFECT OF THERMAL MASS ON MICROSCALE HEAT CONDUCTION

Based on a novel concept named thermal mass, the differential equation of one-dimensional steady heat conduction which includes the variation of the kinetic energy of the thermal mass along the heat flow direction is obtained. The equation shows that the Fourier law is applicable only if the variation of the thermal mass kinetic energy is much smaller than that of the potential energy in heat conduction process. Under conditions of super-high heat flux and ultra-low temperature, the variation of the thermal mass kinetic energy should not be ignored, which leads to a nonlinear relationship between the heat flux and the temperature gradient. It also indicates that in this case the method of measuring the thermal conductivity based on the Fourier law is no longer valid. A correction equation taking the kinetic energy effect into account for calculating the thermal conductivity is presented in this paper. Molecular dynamics simulations are also carried out to confirm the kinetic energy effect.