DTSi Chilled Water Storage

The mechanisms that operate in a Stratified Water Thermal Energy Storage (TES) System are related to both the physical properties of fresh water and the hydraulic characteristics of the stratification inducing pipework. The two physical properties of water that are of special interest to the TES design engineers are:

  1. The Density as it varies with Temperature.

  2. The Kinematic Viscosity at it varies with Temperature.

These two properties provide the basic mechanism for successfully stratifying water of different temperature within a single containment vessel. The density difference between two liquids at different temperature creates buoyancy forces, which cause the warm liquid to be literally floated on top of the cool liquid. The relatively large difference in Kinematic Viscosity of liquids separated only by a few degrees in temperature suppresses any mixing of the two fluids, due to flow disturbances and free convection at the vessel walls. The two properties of water of interest both vary in the direction of increased temperature that makes water the ideal candidate for TES Systems. That is, Density and Kinematic Viscosity both decrease with increased temperature above 4.0°C.

DTSI CHWS tank incorporates a water distribution system including a generally centrally positioned, vertically-oriented pipe extending from the bottom to about the top of the tank. A flange is positioned about mid-way of the pipe for separating an upper section of the pipe from a lower section. A water return line is coupled to the pipe above the flange and a water extraction line is connected to the pipe below the flange.


A plurality of circumferential spaced cool water conduits are connected to the pipe generally adjacent to the top of the tank. Each of the conduits comprises a first section radially extending from the pipe, a 90° elbow coupled to the first section and a bell-shaped diffuser coupled to the elbow. An apparatus is connected between each outlet and a tank support structure holds each of the upwardly turned outlets in a common horizontal plane. The support apparatus positions each of the outlets in a level plane so that water exiting the outlets flows uniformly from all edges of each outlet.