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Thermal Energy Storage(TES) systems are accumulators that store available thermal energy to be used in a later stage when consumption is required or when energy generation is cheaper. Water Thermal Energy Storage is used to increase capacity and lower operating costs of direct energy systems.Thermal energy (chilled water or hot water) is produced during periods of off-peak electrical demand (or usage), collected in a thermal energy storage tank, then withdrawn and distributed to the facility during on peak periods.


These devices need to be constructed to develop and sustain the various layers at the highest expected flow rate throughout the storage period. The diffuser selected for the inflow and outflow of the tank can help to improve the stratification of the tank and increase system efficiency. The diffusers used with chilled water TES tanks include;

  • Radial Diffuser

  • Slotted Diffuser

For the warm water floats on top of the cold water,these diffusers have to keep the velocity low enough that buoyancy prevails over inertia, creating a current across the top or bottom of the tank


For cylindrical tanks, a radial diffuser is the best option. In line with its name, water spreads radially within the tank after being introduced along the diffuser plate. The stability and study design of a radial diffuser can help withstand any hiccups in the system like water surges and hammers.

A radial disk diffuser generally includes two circular plates arranged parallel to each other, or a single disk parallel to the top or bottom tank surface. The disks form a path for the water entering, or exiting, the tank. At the top of the tank, the surface of the water may form a spreading surface, whereas, with the tank bottom, the floor of the tank may form a dispersing surface below the diffuser, which forms the channel. The radial diffuser has an area about 5 times greater than that of the influent pipe, allowing the water to slow significantly before flowing into the tank and redirecting it to a more substantial portion of the tank. Radial disk diffusers are relatively simple in both structure and installation, yet highly effective. They stand up well to water hammer and surging and are best suited to tanks where this may be a problem. However, these diffusers may be difficult to install and can be expensive; therefore, it is essential to ensure that this is the correct diffuser for your application.


Slotted diffuser design requires more installation but can be adapted to different tank shapes. This diffuser is made up of one of more concentric slotted octagonal pipe rings, within water withdrawn through transverse slots in the diffuser piping walls. These parameters may include the intended application or use of the tank, surrounding conditions, shape, capacity, and the position and inlet velocity of diffusers. As its name implies, this type of diffuser consists of slotted pipes formed into ring shapes mounted horizontally in the centre of the tank. The slots in the pipe of the diffuser face the side of the tank where the diffuser is mounted, top or bottom. The flow enters the tank through these slots, where it becomes dispersed along the vertical surface of the tank. These diffusers require more precise design than radial diffusers but usually get better performance results. Slotted diffusers are more vulnerable to the shock of water surges and experience a higher pressure drop than radial diffusers.

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