基于热质理论的广义热弹性动力学模型

Dynamic model of generalized thermoelasticity based on thermal mass theory

具有微尺度传热特征的超常传热过程中,热流矢与温度梯度之间存在延迟效应,且热流的运动受到空间效应的影响.基于热质概念的普适导热定律,结合Clausius不等式和Helmholtz自由能公式,构建了计及热流矢和温度对时间和空间惯性效应的广义热弹性动力学模型,推导了各向同性材料超常传热行为的热弹性控制方程组.通过与已有广义热弹性动力学模型进行对比分析可得,当热流密度不大的条件下,热流矢与温度对空间的惯性效应可忽略时,基于热质概念的广义热弹性模型可分别退化为L-S,G-L和G-N的模型;对于尺度微观、稳态导热条件时,热流矢与温度对空间的惯性效应不可忽略,此时导热系数将受到热质运动惯性效应的影响,利用所建模型可揭示稳态导热时呈现的非傅里叶现象,并可避免基于已有广义模型得到的导热系数随结构特征尺寸变化的非物理现象.

A lagging response in time exists between the propagation of heat flux and the establishment of temperature gradient and it is affected by the space effect during the heat conduction with the micro-scale property. Based on the general heat conduction law of thermal mass, the dynamic model of generalized thermoelasticity is established by Clausius inequality and Helmholtz free energy, where the inertia effect on the time and space of heat flux and temperature is involved. The guiding equations are derived and given for the isotropic and homogeneous materials. By comparison with the existing models of generalized thermoelasticity, the guiding equations can reduce to the L-S, G-L and G-N models when the heat flux is not very high, so that the inertia effect on space of heat flux and temperature can be ignored. For micro-scale heat conduction, the heat flux may be very high and the inertial force due to the spatial velocity variation cannot be ignored, the non-Fourier phenomenon will take place even under steady state condition. In such cases, the thermal conductivity is affected by the inertia effect of the space, which can be explained by the model established in the paper. Meanwhile, the physically impossible phenomenon that thermal conductivity changes with structure size induced by existing generalized model can also be eliminated.