Parametric Study of Charging Inlet Diffuser Performance in Stratified Chilled Water Storage Tanks with Radial Diffusers: Part 2–Dimensional Analysis, Parametric Simulations and Simplified Model Development

A parametric study of the thermal performance during charging of a full-scale radial inlet diffuser in a cylindrical stratified chilled water storage tank was performed by applying factorial experimental theory to the results of simulations performed with a validated computational fluid dynamics (CFD) model. Part 1 describes the development and validation of the CFD model. Part 2 summarizes the results of the parametric study. Dimensional storage tank and inlet diffuser parameters having the potential to influence inlet thermal performance were identified, then formed into dimensionless groups using Buckingham Pi analysis. These included the inlet Richardson number (Ri), inlet Reynolds number (Rei), ratio of diffuser radius to tank radius (RD/Rw) and ratio of diffuser radius to diffuser inlet height (RD/hi). Thermal performance was measured in terms of thermocline thickness and equivalent lost tank height. Sixteen simulations comprising a full 2k factorial experiment were completed and analyzed. Parameter ranges considered were as follows: Ri from 1.0 to 11.1, Rei from 1,000 to 12,000, RD/Rw from 0.2 to 0.4 and RD/hi from 5 to 10. Within these ranges, Ri, RD/Rw and RD/hi were found to be of first-order significance while Rei was not. Regression models of thermal performance metrics as functions of Ri, RD/Rw and RD/hi that are sufficiently simple to be useful for design were developed. These models agreed well with CFD simulations from which they were derived and with field data.