THE MOLECULAR THEORY OF STRUCTURAL RELAXATION AND TRANSPORT PHENOMENA IN LIQUIDS .2. THERMOTRANSPORT DYNAMIC PROCESS IN CLASSICAL LIQUIDS

Thermoelastic properties of classical liquids are investigated on the basis of generalized kinetic equations. Thermotransport in dynamic processes is shown to be characterized by a complex themoconductivity coefficient. Its real part gives the thermoconductivity dynamic coefficient, and the imaginary part gives the dynamic thermal modulus of elasticity. The asymptotic behaviour of the thermoelastic properties is examined; the thermoconductivity of liquids is determined to play the principal part in the domain of low frequencies in the dynamic process of heat transport, whereas in the domain of high frequencies its thermal elasticity modulus plays the main part. The mechanism of heat transport is shown to change from the diffusion one into the wave one in the domain of high frequencies. An analytical expression of the high-frequency velocity of heat waves in liquids is obtained. The expressions obtained for liquid Ar in a wide range of thermodynamic changes are calculated, and their results are compared to the available literature data.