Influence of porosity and permeability of flow distributor on thermal stratification in single media storage tank

Abstract

A single media single tank system is emerging as a promising technology for thermal energy storage. The incorporation of a porous flow distributor in such a system leads to significant improvement of the thermal stratification in the tank. The performance of the flow distributor depends upon the porous structure of the distributor wall. The influence of the distributor on the thermal stratification is well documented; however, the combined effect of porosity and permeability on the thermocline thickness is not yet explored. The objective of the present study is, therefore, to investigate the interdependent effect of the permeability and porosity of the distributor wall on the thermal stratification in the single media single tank storage system. A numerical analysis is performed to evaluate the establishment and progress of thermocline in the storage tank for a wide range of wall-permeability of the vertically mounted flow distributor. The performance of the flow distributor in minimizing the mixing is analyzed through the velocity and temperature fields, stratification number, MIX number, and span of the logistic cumulative distribution function. Results show that the permeability in the range between 10−9 m2 and 10−8 m2, leads to the best thermal stratification and minimum mixing of energy among the given system configurations. Also, the minimal thermocline thickness is achieved to be ∼13% of the entire tank height which is, to the best of our knowledge, considerably lower than the reported value in literature.