Temperature profiles in a full-scale, naturally stratified, chilled-water thermal storage tank are described. Tests were performed using a 1.4 million gallon (5,300 m³), 44.5 ft (13.56 m) water depth cylindrical tank with radial diffusers. Nine charge and discharge cycle tests were performed for various flow rates, covering and extending beyond the normal operating range of the system. A method for obtaining thermocline thickness from field data was derived, and a relationship between inlet flow rate and initial thermocline thickness was established. Significant differences between profiles obtained for charge and discharge cycles at similar flow rates suggest that the free surface at the top of the tank allows more mixing to occur near the upper diffuser. A study of thermocline growth compares measured temperature profiles with those predicted by a numerical conduction model that uses temperature profiles measured early in the cycle as an initial condition. Comparison with the numerical study shows that, for high flow rate tests, large-scale mixing induced by the inlet diffuser can have significant effects on thermocline development, even after the thermocline has moved away from the inlet diffuser.

Units: Dual