Sensitivity analysis of the numerical study on the thermal performance of a packed-bed molten salt thermocline thermal storage system

In this paper, a comprehensive transient, two-dimensional, two-phase model for heat transfer and fluid dynamics within the packed-bed molten salt thermocline thermal storage system is presented. After model validation, the developed model is used to investigate the general thermal behavior of a discharging process of the pack-bed thermocline system and evaluate the interstitial heat transfer coefficient, the effective thermal conductivity and effect of the thermal conductivity of solid fillers. The results show that the thermocline region is moving upward with slight expansion during the discharging process. With the use of two insulation layers, a uniform cross-sectional temperature distribution is well achieved. The use of different correlations for the interstitial heat transfer coefficient or the effective thermal conductivity from the literature leads to negligible difference in the predicted thermal performance. It is also found that decreasing the heat transfer rate between fluid and solid fillers, or increasing the thermal conductivity of solid fillers, results in an increase in the thermocline thickness which finally decreases the effective discharging time and the effective discharging efficiency.

► We present a transient 2-D two-phase model for the packed-bed thermocline system.
► We investigate the general thermal behavior of a discharging process.
► We evaluate several heat transfer correlations and parameters.
► Solid conductivity and interstitial heat transfer influence the thermocline thickness.