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 (Re_i), ratio of diffuser radius to tank radius (R_D/R_w) and ratio of diffuser radius to diffuser inlet height (R_D/h_i). Thermal performance was measured in terms of thermocline thickness and equivalent lost tank height. Sixteen simulations comprising a full 2^k factorial experiment were completed and analyzed. Parameter ranges considered were as follows: Ri from 1.0 to 11.1, Re_i from 1,000 to 12,000, R_D/R_w from 0.2 to 0.4 and R_D/h_i from 5 to 10. Within these ranges, Ri, R_D/R_w and R_D/h_i were found to be of first-order significance while Re_i was not. Regression models of thermal performance metrics as functions of Ri, R_D/R_w and R_D/h_i 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.

Reprinted from the International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research, Vol. 7, No. 1, January 2001, pp. 51-65.

Units: Dual