Electrohydrodynamic enhancement of phase change material melting in cylindrical annuli under microgravity

Abstract

Latent heat thermal energy storage has been recommended as an effective technology for the thermal management system of space exploration for its excellent ability to store thermal energy. However, the low thermal conductivity of phase change material seriously weakens the heat charging and discharging rates of the system. This paper introduces electrohydrodynamic, a popular active heat transfer enhancement technology, to enhance the phase change material melting in a shell-tube latent heat storage system under microgravity using the lattice Boltzmann method. Different from some previous works, this work mainly focuses on the combined effects of the electric Rayleigh number T and different gravity conditions on the melting performance. Results indicate that the electrohydrodynamic technique always shows good performance in accelerating the melting process, and especially, it is possible to save up to 90% of the charging time in some cases. In addition, the effect of eccentricity on the charging process is investigated, and it is found that although the concentric annulus is always the optimal configuration under no-gravity conditions, the optimal eccentric position of the internal tube largely depends on the electric Rayleigh number if one takes into account the gravity effects. Moreover, the effect of radius ratio Γ on the heat storage efficiency is also evaluated under no-gravity condition. The present work illustrates that electrohydrodynamic is an effective method for enhancing phase change material melting even under microgravity. • The combined effect of Coulomb force and gravity on PCM melting is studied. • The transient charging process of PCM melting under an electric field is presented. • A maximum of over 90% melting time saving can be observed under an electric field. • The optimal eccentric position relies on the gravity condition.