Optimized flow distributor for stabilized thermal stratification in a single-medium thermocline storage tank: A numerical and experimental study

This paper investigates the impact of flow injection on the temperature stratification inside single-medium thermocline storage tanks. Special focus is given on how to maintain the stable thermocline evolution during the dynamic charging or discharging operation, by using a new type of fluid diffuser, namely the Ring-Opening Plate Distributors (ROPDs). Firstly, the ROPDs are designed and the size distribution of the ring-shape openings is optimized by a simulation-based optimization algorithm. This diffuser concept has then been validated experi-mentally, showing its effectiveness in improving the charging and discharging efficiency of a laboratory-scale storage tank by up to 14.5% and 19.8%, respectively. Systematic experiments are performed to examine the effects of the injecting flow rate and temperature on the local transient temperature profiles and on the energy and exergy efficiencies of the thermocline tank. The stability range of operational parameters, characterized by the bulk Froude number (Fr < 3), has been deter-mined for quasi-undisturbed advance of the thermocline. Beyond this stability range, simple tube-type diffuser is no longer capable of mitigating the impact of inflowing thermal jet. Additional structuration and optimization of the diffuser geometry become essential to stabilized the thermal stratification and to maintain a good thermal performance of the storage tank.