Cascade Systems

The VS 3010 BS pack controller regulates complete cascade systems, incl. the cascade heat exchanger. (Diagram: Eckelmann AG)

New E*LDS pack controller VS 3010 BS from Eckelmann simultaneously regulates the cascade heat exchanger.

Wiesbaden, 27/03/2013: The new VS 3010 BS pack controller (version 4.35 and higher) from Eckelmann AG now provides all the control functions for cascade systems on one platform – with integrated cascade heat exchanger regulation. Low- and high-temperature circuits can now be coordinated in a highly dynamic and energy efficient manner.

The VS 3010 BS is characterised by a high control quality, as well as saving investment costs as no extra case controller is required for the heat exchanger. Highlights include the forward-looking power adjustment of the compressors for the top and bottom stages, as well as continuous control of the evaporator side of the cascade heat exchanger. The VS 3010 BS’s universal regulation concept ensures an especially robust cascade operation as the intelligent pack controller from Eckelmann’s E*LDS system controls all cascade functions completely independent of the field bus communication.

The pack controller can be universally deployed, for example for refrigeration systems employing R744 (CO2) for the low-temperature refrigeration (subcritical) and a synthetic refrigerant such as R134a for normal-temperature refrigeration.

Proven greater efficiency

Cascade refrigeration systems consist of two thermally connected circuits. The condensation heat from the low-temperature circuit is transferred to the high-temperature circuit via a cascade heat exchanger; cascade heat exchangers are condensers and evaporators in one. The lower circuit generally employs a refrigerant with a high vapour pressure (e.g. CO2), and the upper circuit a refrigerant with a lower vapour pressure (e.g. R134a or R404A).

Thanks to the active condensation of the refrigerant in the low-temperature circuit it is possible to generate lower condensation temperatures than condensation in the external air. This reduces the difference between condensation and evaporation pressure (Δpc-po), and thus improves the efficiency, i.e. COP of the low-temperature circuit.

In order to ensure the energy-efficient operation of cascade systems the compressor output of both circuits must be coordinated in a highly dynamic and load adjusted manner. Furthermore, the evaporation and condensation temperatures in the evaporator-condenser must be regulated so that the temperature difference between the condenser and evaporator sides is only of the order of a few degrees Kelvin. This increases the energy efficiency of the cascade heat exchanger and thus the overall efficiency of the cascade system.

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