Papers by Keyword: Solid-Liquid

Abstract: The paper features the mathematical model of analytical calculation of thermodynamic properties like viscosity, speed of sound and thermal conductivity for fluids in one and two-phase region (fluid-solid, fluid-gas) on the basis of statistical mechanics. For the calculation of thermal conductivity and viscosity for fluids will be presented Chung-Lee-Starling model Equations for the thermal conductivity are developed based on kinetic gas theories and correlated with the experimental data. The low-pressure transport properties are extended to fluids at high densities by introducing empirically correlated density dependent functions. These correlations use acentric factor, dimensionless dipole moment and an empirically determined association parameters to characterize molecular structure effect of polyatomic molecules. The calculation of thermodynamic properties for fluids was developed under the theory of statistical thermodynamics and statistical associated fluid theory. For the calculation of thermal conductivity of solids are the most important two contributions: the heat transport by electrons (el) and by phonons (ph). In our model we have made the assumption that heat transport by electrons and by phonons is independent and the thermal conductivity is than a sum of both terms.

Abstract: Three thermal modeling methods for phase change materials (PCMs): enthalpy-based method, effective heat capacity method and apparent heat capacity method, are presented in details. Their characteristics and application limitations are compared and discussed. We found that enthalpy-based method and effective heat capacity method are both approximation treatments, and can be well used in steady state problems, while apparent heat capacity method tracks the moving phase change boundary in PCMs, and it is the most accurate and applicable method of the three for dealing with transient processes. This work might provide useful information for the study of using PCMs in temperature control field, especially in aircraft environmental temperature control and thermal management.

Abstract: The effects of reheating in solid-liquid region on the microstructure of electromagnetically stirred Al alloy have been investigated. The billet of Al alloy was produced at a various casting speed from 200 to 500 mm/min in a continuous casting machine with an electromagnetic stirring device. The microstructure of the billet, which was isothermally reheated in a solid-liquid region during holding for from 0.5 to 15 min, was examined. The roundness and size of primary α phase of electromagnetic stirred Al alloy was measured according to the reheating time. The roundness of primary α phase was obtained a minimum during holding for from 3 to 7 min at a holding temperature of 584°C and was deteriorated at a longer reheating time due to a dominant coalescence. Also the spheroidization of primary α phase during reheating in solid-liquid region was significantly dependent on initial microstructure of the billet.