A parametric investigation of melting process within a porous medium under local thermal non-equilibrium condition using LBM

Document Type : Research Article

Authors

Faculty of Engineering, University of Zanjan, Zanjan, Iran

Abstract

The use of a porous medium with a high conductivity improves the rate of heat transfer in latent energy storage systems. This paper investigates the melting of the phase change material inside a porous medium under the local thermal non-equilibrium condition with the lattice Boltzmann method. Results examine the effect of Rayleigh number, porosity ratio, pore size, and Sparrow number on the liquid fraction and position of melting front. Results show that by increasing the pore diameter, the interface of the two phases tends to bend but the liquid fraction decreases. Also, it is found that the difference between the liquid fraction in the presence and absence of natural convection for Ra<106, is less than 5%. Nonetheless, by increasing the Rayleigh number to 108, this difference at Fo=0.003 is more than 14% and at Fo=0.006 will reach more than 31%. Furthermore, in Ra=108 and for small Sparrow numbers, this difference is small and intensifies with increasing the Sparrow number. Also, by reducing the Darcy number, natural convection is weakened and it can be ignored for Da<10-4. It is shown that in small Darcy numbers Da=10-4, the deviation from the pure conduction is always increased by Sparrow number, and for larger Darcy numbers Da=10-2, this deviation has a maximum value of 53% at Fo=0.003 and 84% at Fo=0.006.

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