Effects of Volume Changes on the Thermal Performance of PCM Layers Subjected to Oscillations of the Ambient Temperature: Transient and Steady Periodic Regimes.

The Stefan problem regarding the formation of several liquid-solid interfaces produced by the oscillations of the ambient temperature around the melting point of a phase change material has been addressed by several authors. Numerical and semi-analytical methods have been used to find the thermal response of a phase change material under these type of boundary conditions. However, volume changes produced by the moving fronts and their effects on the thermal performance of phase change materials have not been addressed.

Thermophysical Characterization of Paraffin Wax Based on Mass-Accommodation Methods Applied to a Cylindrical Thermal Energy-Storage Unit.

Two mass-accommodation methods are proposed to describe the melting of paraffin wax used as a phase-change material in a centrally heated annular region. The two methods are presented as models where volume changes produced during the phase transition are incorporated through total mass conservation. The mass of the phase-change material is imposed as a constant, which brings an additional equation of motion.

Effects of Total Thermal Balance on the Thermal Energy Absorbed or Released by a High-Temperature Phase Change Material.

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.

Modeling the release of curcumin from microparticles of poly(hydroxybutyrate) [PHB].

Polyhydroxybutyrate (PHB) is biodegradable and biocompatible polyester that has been recently used for developing different drug delivery systems (DDS). Microspheres as DDS, consist of a polymeric matrix with a diameter of 1-125 μm which contains a substance entrapped, and then released mainly through diffusion. In order to make DDS viable for commercial applications, it is essential to develop models that describe and predict the substance release kinetic.

Effects of Pressure-Induced Density Changes in the Thermal Energy Absorbed by a Micro-Encapsulated Phase-Change Material.

Density changes produced by pressure increments during melting of a spherically confined phase-change material have an impact on the thermal energy absorbed by the heat storage unit. Several authors have assumed incompressible phases to estimate the volume change of the phase-change material and the thermal balance at the liquid⁻solid interface. This assumption simplifies the problem but neglects the contribution of density changes to the thermal energy absorbed.