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  The STL consists of two parts
  Principle of operation

Principle of operation

The opposite mentioned histogram represents a typical cooling profile for an air conditioned office. The STL facilitates effective energy management and typical operational cycles are hereby explained for the parallel hydraulic layout. Alternative hydraulics and operational mode may be appropriate in some industrial applications.

There are 4 different kinds of systems (see the legend after the pictures) : 

Click here to see the description of the Series Upstream Layout

Series Upstream


This layout can be used for any AC or refrigeration systems. It is very popular for large systems such as District Cooling Systems (DCS).

This layout has the lowest first cost.
     This layout is interesting when the difference (DT = Treturn - Tleaving) is higher than 8°C. The chiller and the STL are in series, the DT is shared between respectively the STL and the chiller. The hydraulic and the control are simple. The advantage of the upstream layout is that the STL works with a high inlet & outlet temperature leading to a higher STL capacity. The flow in charge and discharge modes through the STL can be reversed by using a 3-way-valve in dividing configuration.
Click here to see the description of the Series Downstream Layout

Series Downstream


This layout can also be used for any AC or refrigeration systems.

This layout allows to reach very high system efficiency.
This layout is also interesting when the difference (DT = Treturn - Tleaving) is higher than 8°C. The chiller and the STL are in series, the DT is shared between respectively the chiller and the STL. The hydraulic and the control are simple. The advantage of the downstream layout is that the chiller works with the highest possible inlet temperature. But the STL volume is slightly higher to cope with the lower inlet temperature. The flow in charge and discharge modes through the STL are also reversed.
Click here to see the description of the Parallel Layout with 1 Set-Point

Parallel Layout With 1 Set-Point


This layout can be used for any AC or refrigeration systems working in partial storage when the demand is always higher than the chiller capacity, or in back-up.

This layout corresponds to a minimum first cost.
The chiller and the STL are in parallel. The chiller set point corresponds to the end of the storage. During the day when there is a demand the chiller leaving temperature is much higher than the set point due to the value of the return temperature (usually 12°C at peak load).
Click here to see the description of the Parallel Layout with 2 Set-Points

Parallel Layout With 2 Set-Points


This layout can be used for any AC or refrigeration systems working with various strategies. 

This layout allows to achieve the best energy management with a high efficiency.
The chiller and the STL are in parallel. The chiller has two set points. One set point corresponds to the charge mode and the second one corresponds to the discharge mode. The distinction between the charge and discharge modes allows an operation with the highest evaporating temperature thus the best efficiency. The control done by the 3-way valve is simple.

 

Legend

      

 

  The STL consists of two parts
  Principle of operation