Sensitivity of Thermal Stratification at the Number of Partition of a Storage Tank

Abstract

This work is set in a series of studies on the influence of different geometrical and physical parameters on the quality of the thermo-hydrodynamic field via the thermal stratification that is installed in thermal energy storage tanks. The idea is based on the fact that undisturbed stratification considerably lengthens the charging/discharging period and therefore satisfies the user's requirements for this stored energy such as hot water. The purpose of this study is to be able to compare between the various configurations and thus to conclude on the optimal configuration before the realization phase. For an aspect ratio A ≤ 3, the central zone always shows the character of a stratification (stratified core), it occupies almost 50% of the enclosure. For 4 ≤ A ≤ 8, the central zone occupies almost 30 to 20% of the enclosure. The aspect ratio influence on the development and preservation (stabilization) of the stratification encouraged us to take advantage of its stratified core creation character but without modification of the shape of the storage tank nor its volume. In order to do this, we opted for a substantially high aspect ratio transformation that disadvantages stratification to a set of superimposed tanks of low aspect-ratio favoring stratification. However, the use of a partitioned configuration for improving the thermal stratification in a hot water storage tank may have originality in itself. In this work, we study the influence of partitions (number of partitions Np ranging from 0 to 7) on the appearance and destruction of stratification in the storage tank. The motion equations have been discretized into algebraic equations using a finite volume approach. To eliminate the pressure oscillations, we adopted the non-shifted grid approach (Colocated Grid) proposed by Rhie and Chow.

Keywords: storage tank, thermal stratification, charge/discharge, thermocline, obstacle plates