Tecnológico de Monterrey, Escuela de Ingeniería y Ciencias, Carr. al Lago de Guadalupe Km. 3.5, State of Mexico 52926, Mexico.
Centro de Investigación en Ciencias, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 52900, Mexico.
Molecules. 2021 Jan 12;26(2):365. doi: 10.3390/molecules26020365.
Front tracking and enthalpy methods used to study phase change processes are based on a local thermal energy balance at the liquid-solid interface where mass accommodation methods are also used to account for the density change during the phase transition. Recently, it has been shown that a local thermal balance at the interface does not reproduce the thermodynamic equilibrium in adiabatic systems. Total thermal balance through the entire liquid-solid system can predict the correct thermodynamic equilibrium values of melted (solidified) mass, system size, and interface position. In this work, total thermal balance is applied to systems with isothermal-adiabatic boundary conditions to estimate the sensible and latent heat stored (released) by KNO3 and KNO3/NaNO3 salts which are used as high-temperature phase change materials. Relative percent differences between the solutions obtained with a local thermal balance at the interface and a total thermal balance for the thermal energy absorbed or released by high-temperature phase change materials are obtained. According to the total thermal balance proposed, a correction to the liquid-solid interface dynamics is introduced, which accounts for an extra amount of energy absorbed or released during the phase transition. It is shown that melting or solidification rates are modified by using a total thermal balance through the entire system. Finally, the numerical and semi-analytical methods illustrate that volume changes and the fraction of melted (solidified) solid (liquid) estimated through a local thermal balance at the interface are not invariant in adiabatic systems. The invariance of numerical and semi-analytical solutions in adiabatic systems is significantly improved through the proposed model.
界面局部热平衡不能重现绝热系统中的热力学平衡状态。通过整个液-固系统的总热平衡可以预测熔化（凝固）质量、系统尺寸和界面位置的正确热力学平衡值。在这项工作中，总热平衡应用于具有等温-绝热边界条件的系统，以估计用作高温相变材料的 KNO3 和 KNO3/NaNO3 盐所储存（释放）的显热和潜热。获得了在界面处进行局部热平衡和在高温相变材料吸收或释放的热能方面进行总热平衡之间获得的解决方案的相对百分比差异。根据所提出的总热平衡，引入了对液-固界面动力学的修正，该修正考虑了相变过程中吸收或释放的额外能量。结果表明，通过整个系统进行总热平衡可以改变熔化或凝固速率。最后，数值和半解析方法表明，通过界面局部热平衡估计的体积变化和熔化（凝固）固体（液体）的分数在绝热系统中不是不变的。通过所提出的模型，显著提高了绝热系统中数值和半解析解的不变性。
