scholarly journals Thermo-elastic model for the prediction of thermodynamic properties of high temperature phase change materials under confinement: Isobaric and isochoric regimes

AIP Advances ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 045329
Author(s):  
Ernesto M. Hernández-Cooper ◽  
José A. Otero ◽  
J. Enrique Chong-Quero
Keyword(s):  
High Temperature ◽  
Thermodynamic Properties ◽  
Phase Change ◽  
Phase Change Materials ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Elastic Model

Research on Expanded Graphite/Nitrate High-Temperature Composite Phase Change Materials

2015 ◽  
Vol 740 ◽  
pp. 11-14 ◽  
Author(s):  
Yue Feng Li
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Phase Change ◽  
Phase Change Materials ◽  
Water Solution ◽  
Expanded Graphite ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Solidification Temperature ◽  
Saturated Water Solution

In order to enhance the thermal conductivity of high-temperature phase change materials (PCMs), expanded graphite (EG) /NaNO3-LiNO3 composite was prepared by the method of eutectic aqueous solution infiltration porous structure of EG. The composites with an EG amount of 10%, 20% and 30% were prepared in the similar way. The results proved that the eutectic was an excellent PCM, for its melting (solidification) temperature was 193.7 (191.7) °C, and its latent heat was 272.6(262.6) kJ/kg. With the increasing in graphite amount, the thermal conductivity of the composite was found to progressively increase with intensifications up to 10. We can conclude that the saturated water solution method was a simple and effective way to strengthen the thermal conductivity of the eutectic.

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

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 365
Author(s):  
Suset Rodríguez-Alemán ◽  
Ernesto M. Hernández-Cooper ◽  
Rolando Pérez-Álvarez ◽  
José A. Otero
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Phase Change ◽  
Thermodynamic Equilibrium ◽  
Thermal Energy ◽  
Phase Change Materials ◽  
High Temperature Phase ◽  
Thermal Balance ◽  
Temperature Phase ◽  
Solid Interface

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.

Sign in / Sign up

Export Citation Format

Share Document